Entire Report - September 2012


National Overview

NCDC transitioned to the nClimDiv dataset on Thursday, March 13, 2014. This was coincident with the release of the February 2014 monthly monitoring report. For details on this transition, please visit our public FTP site and our U.S. Climate Divisional Database site.

Maps and Graphics

Temperature and Precipitation Ranks
U.S. Percentage Areas
More Information

National Overview:



September Extreme Weather/Climate Events
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Did You Know?

USHCN Version 2.5 Transition

Since 1987, NCDC has used observations from the U.S. Historical Climatology Network (USHCN) to quantify national- and regional-scale temperature changes in the conterminous United States (CONUS). To that end, USHCN temperature records have been "corrected" to account for various historical changes in station location, instrumentation, and observing practice. The USHCN is a designated subset of the NOAA Cooperative Observer Program (COOP) Network. USHCN sites were selected according to their spatial coverage, record length, data completeness, and historical stability. The USHCN, therefore, consists primarily of long-term COOP stations whose temperature records have been adjusted for systematic, non-climatic changes that bias temperature trends.

The National Climatic Data Center periodically improves the quality of the datasets maintained at the center and releases updated versions. Beginning with the September 2012 processing, NCDC will use USHCN version 2.5 for national temperature calculations as well as in other products, including Climate at a Glance and the Climate Extremes Index. For additional information on the improvements made to USHCN version 2.5, please visit USHCN.

More about climate monitoring…

Supplemental September, Warm Season, and January-September Information


Please Note: the US national ('CONUS') temperatures associated with the September 2012 release were initially incorrect. NCDC personnel used an incorrect base period as the basis of their calculation. This error was corrected on October 19, 2012. The general character of monthly temperature anomalies (departures from normal) and associated trends were not affected by this error, as it applied equally to all Septembers on the record. The slight changes in the anomalies and associated ranks with the October 19 correction are reflective of late-arriving data, and are typical. The statistics in this report were updated on October 19, 2012.

  • Climate Highlights — September
  • The average contiguous U.S. temperature during September was 66.3°F, 1.5°F above the 20th century average, the 18th warmest such month on record. September 2012 marks the 16th consecutive month with above-average temperatures for the Lower 48.
  • The average contiguous U.S. temperature during September was 67.0°F, 1.4°F 66.25°F, 1.5°F above the 20th century average, tying September 1980 as the 23rd, the 18th warmest such month on record. September 2012 marks the 16th consecutive month with above-average temperatures for the Lower 48.
  • Higher-than-average temperatures were anchored across the West during much of September with California, Nevada, Utah, and Wyoming experiencing a top ten warm September. Monthly temperatures were below average across the Midwest and Ohio Valley.
  • The September nationally-averaged precipitation total of 2.40 inches was slightly below the long-term average.
  • Record and near-record dry conditions were experienced from the Pacific Northwest, across the Northern Rockies and Plains, and into the Upper Midwest. Minnesota, Montana, North Dakota, and South Dakota were record dry for September. Six additional adjacent states, from Washington to Wisconsin, had precipitation totals among their ten driest.
  • The Ohio Valley was wetter than average during September, where Ohio and Kentucky both had monthly precipitation totals ranking among their ten wettest.
  • Several large extra-tropical cyclones affected Alaska during September, bringing heavy precipitation to the state. The Alaskan statewide average precipitation was 48 percent above the 30-year average, and ranked as the 5th wettest September in its 95-year period of record.
  • According to the October 2, 2012 U.S. Drought Monitor, 64.6 percent of the contiguous U.S. was experiencing moderate-to-exceptional drought, slightly larger than the extent of drought at the end of August. The percent area of the nation experiencing exceptional drought, the worst category of drought, remained nearly constant at about 6 percent. Exceptional drought conditions improved across the Lower-Mississippi Valley and Ohio Valley, while drought conditions deteriorated across the Central and Northern Plains.
  • The warm and dry conditions across the Northwest were associated with another month of above-average wildfire activity. Nationally, nearly 1.1 million acres burned during September, the 3rd most on record for the month. Idaho, Montana, Oregon, and Washington experienced the brunt of the large wildfire activity.
  • A list of select September temperature and precipitation records can be found here.
  • Climate Highlights — warm season (April-September)
  • The contiguous U.S. warm season, defined as the six-month period from April-September, had temperatures that were record warm. The six-month average temperature of 67.6°F for the Lower 48 was 2.7°F above average. The previous warmest April-September occurred in 2006 when the nationally-averaged temperature was 67.0°F.
  • The warm season brought above-average temperatures to a large portion of the country, with 33 states having six-month temperatures among their ten warmest. Colorado and Wyoming were both record warm with temperatures 4.2°F and 4.4°F above average, respectively.
  • The April-September period was the 14th driest on record for the contiguous U.S. with a national precipitation total of 14.41 inches, 1.62 inches below average. Below-average precipitation was observed across the central regions of the country stretching from the Lower-Mississippi River Valley into the Northern Rockies. Nebraska and Wyoming were both record dry for the period. Nebraska's statewide precipitation total of 9.24 inches was 8.16 inches below average, while Wyoming's precipitation total of 3.98 inches was 4.5 inches below average.
  • The U.S. Climate Extremes Index (USCEI), an index that tracks the highest and lowest 10 percent of extremes in temperature, precipitation, drought and tropical cyclones across the contiguous U.S., was more than twice the average value during the warm season, and marked the highest USCEI value for the six-month period. Extremes in warm daytime temperatures, warm nighttime temperatures, and the spatial extent of extreme drought contributed to the record high USCEI value, based on data from 1910-2012.
  • Climate Highlights — Year-to-Date (January-September)
  • The January-September period was the warmest first nine months of any year on record for the contiguous United States. The national temperature of 58.9°F was 3.8°F above the 20th century average, and 1.3°F above the previous record warm January-September of 2006. During the nine-month period, 46 states had temperatures among their ten warmest, with 25 states being record warm. Only Washington had statewide temperatures near average for the period.
  • January-September 2012 was the 11th driest such period on record for the contiguous U.S. with a precipitation total 1.98 inches below the average of 22.67 inches. The central portion of the country, from the Ohio Valley to the Rocky Mountains, was drier than average. Wetter-than-average conditions were observed along the Gulf Coast and in the Pacific Northwest.
  • The USCEI was more than twice the average value during the January-September period, and marked the highest USCEI value for the period. Extremes in warm daytime temperatures and warm nighttime temperatures contributed to the record high USCEI value.
  • Climate Highlights — 12-month period (October 2011-September 2012)
  • The October 2011-September 2012 period was the warmest such 12-month period on record for the contiguous U.S., with an average temperature of 55.3°F, 3.3°F above average. This 12-month temperature average was the 3rd warmest of any 12-month period on record for the contiguous United States. The six warmest 12-month periods have all ended during 2012.

Alaska Temperature and Precipitation:

  • Alaska had its 46th coolest September since records began in 1918, with a temperature 0.2°F (0.1°C) below the 1971–2000 average.
  • Alaska had its 36th coolest July-September since records began in 1918, with a temperature 0.9°F (0.5°C) below the 1971–2000 average.
  • Alaska had its 18th coolest January-September since records began in 1918, with a temperature 2.0°F (1.1°C) below the 1971–2000 average.
  • Alaska had its 5th wettest September since records began in 1918, with an anomaly that was 48.1 percent below the 1971–2000 average.
  • Alaska had its 6th wettest July-September since records began in 1918, with an anomaly that was 31.0 percent above the 1971–2000 average.
  • Alaska had its 19th wettest January-September since records began in 1918, with an anomaly that was 17.0 percent above the 1971–2000 average.

For additional details about recent temperatures and precipitation across the U.S., see the Regional Highlights section below and visit the Climate Summary page". For information on local temperature and precipitation records during the month, please visit NCDC's Records page. For details and graphics on weather events across the U.S. and the globe please visit NCDC's Global Hazards page.


Regional Highlights:

These regional summaries were provided by the six Regional Climate Centers and reflect conditions in their respective regions. These six regions differ spatially from the nine climatic regions of the National Climatic Data Center.

  • Northeast Region: (Information provided by the Northeast Regional Climate Center)
  • September's average temperature of 61.2 degrees F (16.2 degrees C) was 0.4 degrees F (0.2 degrees C) above normal. This is the third month in a row to average warmer than normal (final data have June 2012 0.1 degree F, 0.1 degrees C below normal). State departures did not stray too far from normal; departures ranged from 0.7 degrees F (0.4 degrees C) below normal in Rhode Island to 1.1 degrees F (0.6 degrees C) above normal in Delaware. January through September averages remain above normal, with the Northeast seeing its warmest January through September since 1895. Among the states, Maine was ranked third warmest, Pennsylvania and West Virginia, 2nd warmest and the rest of the states joined the region in first place.
  • Overall, the Northeast averaged wetter-than-normal during September,. The monthly total of 5.02 inches (127 mm) was 128 percent of the normal precipitation amount. This placed September 2012 as the 18th wettest September in 118 years. Totals in Delaware and New Jersey were just below normal, or 97 percent, while rainfall departures in the rest of the region ranged from 101 percent in Maryland to 157 percent in West Virginia. It was the 11th wettest September since 1895 in West Virginia.
  • Above normal rainfall during September alleviated drought conditions in much of the Northeast. According to the US Drought Monitor issued on October 2, 2012, southern Delaware was still experiencing moderate (D1) and severe (D2) drought. Conditions in southern Maryland improved to a mix of D0 and D1, with only a very small D2 area along the border with Delaware. Portions of upstate New York, mainly east of Lakes Erie and Ontario, were still experiencing moderate drought (D1) at month's end.
  • The Northeast saw its share of severe weather during September, including at least five confirmed tornados, several waterspouts and funnel clouds, damaging winds, and flash flooding. The first week of the month saw an EF0 tornado in Delaware on the 3rd, and two tornados, an EF0 and EF1 in the New York City metro area on the 8th. The main impact from these tornados was downed trees and power lines along with minor structural damage along with a few minor injuries. In addition to the tornados, hundreds of wind damage reports were received from spotters throughout the region. Passage of a strong cold front on the 18th resulted in blustery conditions and intense rainfall, primarily focused on the eastern part of the region from Massachusetts to Maryland. Strong southerly winds ahead of the front gusted up to 61 mph (27 m/s) with sustained winds as high as 33 mph (15 m/s) at the higher elevations. Downpours of 2-4 inches (50-100 mm) closed roads throughout the region, while downed trees injured one person in Camden County, NJ and two in Delaware County, PA. Interstate 95 in Connecticut was closed in Cos Cob by downed trees and in Norwalk, CT due to flash floods. An unstable airmass on the 27th led to the formation of two weak tornados in southwestern Pennsylvania. A day later, another intense rain event flooded roads in southeastern New York and southwestern Connecticut, including I-95 and the Hutchinson River Parkway.
  • For more information, please go to the Northeast Regional Climate Center Home Page.
  • Midwest Region: (Information provided by the Midwest Regional Climate Center)
  • The Midwest regional temperature was slightly below normal in September, breaking a string of 11 straight months above normal from October 2011 to August 2012. For the first time since January 2011, none of the nine Midwest states had an above normal statewide temperature. September temperatures ranged from near normal to 3 degrees F (2 C) above normal near Lake Superior. Temperatures were above normal early in the month but the latter part of the month was cooler than normal. Despite the cool September, statewide year-to-date temperatures rank as the warmest or second warmest in the 118-year history for each Midwest state.
  • September precipitation varied drastically from dry in the north to wet in the south. Minnesota recorded its driest September on record (118 years) with many stations recording less than a half inch (13 mm) of rain while precipitation totals in southern Illinois topped 14 inches (356 mm) at several stations. As a percentage of normal, the totals ranged from less than 10 percent to more than five times normal. Heavy September rains in Ohio (4th wettest) and Kentucky (7th wettest) were in contrast to the drier conditions to the north where Minnesota recorded its driest September and Wisconsin had its 9th driest. June to September was the driest on record in Iowa and May to September was the third driest in Missouri. Year-to-date precipitation totals rank among the top 12 driest years since 1895 in five states: Iowa (4th), Illinois (7th), Missouri (8th), Indiana (12th), and Wisconsin (12th).
  • Early freezes hit Minnesota, Wisconsin, and Iowa with the most widespread event on the 23rd and 24th. The freeze was weeks ahead of normal with many locations in Iowa recording their earliest freeze since 1983. Early crop maturity helped to limit the damages.
  • Drought conditions eased in the southern half of the region but further north there was both expansion and intensification of drought. Overall, the Midwest saw an increase from 82 percent to 91 percent of the region in drought during September but severe drought dropped from 50 to 42 percent and extreme drought dropped from 33 to 15 percent. Missouri saw the biggest improvements going from 97 to just 17 percent areal coverage of extreme drought, though the entire state remained in drought. Minnesota saw the biggest expansion and intensification with drought areas increasing from 38 to 96 percent of the state and extreme drought increasing from 0 to 20 percent. Improvements in the southern parts of the Midwest came too late in the year to help the corn crop.
  • Harvest was on pace or ahead of normal for major crops in the Midwest. Corn harvest was ahead of normal across the region. Soybean harvest was near normal in the southeast but well ahead of normal in the northwest.
  • For details on the weather and climate events of the Midwest, see the weekly summaries in the Midwest Climate Watch page.
  • Southeast Region: (Information provided by the Southeast Regional Climate Center)
  • For the second straight month, mean temperatures were near normal across much of the Southeast region. The greatest departures were found across parts of Alabama, North Carolina, and southern Florida, where monthly temperatures were between 1 and 2 degrees F (0.5 and 1.1 degrees C) below normal. In contrast, monthly temperatures were 1 degree F (0.5 degrees C) above normal across northern Florida, central parts of Georgia and South Carolina, and northern Virginia. Monthly temperatures were also above normal across Puerto Rico and the U.S. Virgin Islands. San Juan, PR, tied its warmest September on record (1898-2012) with a mean temperature of 84.9 degrees F (29.4 degrees C). The warmest weather of the month occurred during the first week, as temperatures reached 95 degrees F (35 degrees C) as far north as central Virginia. The coolest weather of the month occurred in the days following the passage of a cold front on the 19th. Temperatures dropped below freezing for the first time this fall across many of the higher elevations of western North Carolina, while temperatures dipped below 50 degrees F (10 degrees C) as far south as the Tampa Bay, FL area.
  • Precipitation in September was highly variable across the Southeast region. The wettest locations were found across Alabama and northwest Florida, where monthly rainfall totals were between 150 and 300 percent of normal. Much of the rainfall in these areas came from the remnants of Hurricane Isaac, which dropped over 6 inches (152.4 mm) of rain locally between the 3rd and 5th of the month. Some locations in central North Carolina also received above normal rainfall in September. Raleigh-Durham, NC, recorded 7.83 inches (198.9 mm) for the month, which was more than 3 inches (76.2 mm) above normal. Much of this rainfall was tied to a low pressure system that moved north out of the Gulf of Mexico on the 18th of the month, resulting in locally heavy rainfall and some severe weather across the Southeast. Strong storms also brought heavy rain to the area on the 28th and 29th of the month. In contrast, the driest locations were found along coastal sections of Virginia and South Carolina, where monthly rainfall totals were less than 50 percent of normal. Charleston, SC, recorded 2.02 inches (51.3 mm) for the month, which was over 4 inches (101.6 mm) below normal, while North Myrtle Beach recorded just 0.87 inches (22.1 mm) for the month, or 14 percent of normal. Precipitation in September was generally below average across Puerto Rico and the U.S. Virgin Islands. Charlotte Amalie Airport in St. Thomas recorded its driest September on record with 0.92 inches (23.4 mm) of rain (period of record 1953-2012). Elsewhere across the region, monthly precipitation was between 50 and 100 percent of normal.
  • There were 208 reports of severe weather across the Southeast in September, with at least one report on half of the days. Most of these reports were for damaging winds. The remnants of Hurricane Isaac contributed to flash flooding, high winds, and small hail across parts of the Florida Panhandle from the 3rd to the 5th of the month. The low pressure system that moved out of the Gulf of Mexico on the 18th contributed to high winds, water spouts, and rip currents (including one fatality) along the Florida Gulf Coast. In addition, two EF-0 tornadoes were confirmed in eastern North Carolina on the 18th of the month. The first touched down near the town of Zebulon in Wake County. No damage was reported. The second tornado touched down three separate times along a five-mile (8.0 km) path near the town of Trenton in Jones County. Most of the damage was limited to large trees and branches, except for a greenhouse and shed that were damaged by flying debris.
  • Drought conditions remained fairly stable across the Southeast in September, with approximately one-third of the region classified in drought (D0 and greater) according to the U.S. Drought Monitor by the end of the month. Wet weather and saturated ground impeded the harvesting of hay, cotton, and peanuts across parts of Alabama, Georgia, and Florida. The planting of sugarcane and winter vegetables was also delayed across parts of Florida due to wet conditions over the past several months. The persistence of wet conditions also contributed to fungal diseases as well as outbreaks of mold and mildew in several different crops across parts of Florida and North Carolina. In contrast, the persistence of dry conditions across central Georgia continued to limit pasture growth.
  • For more information, please go to the Southeast Regional Climate Center Home Page.
  • High Plains Region: (Information provided by the High Plains Regional Climate Center)
  • While most the High Plains Region had near normal average temperatures, September 2012 continued to be dry. Most locations in the Region had average temperatures which were within 1.0-2.0 degrees F (0.6-1.1 degrees C) of normal. The largest temperature departures occurred in a few areas of Wyoming, where average temperatures were over 4.0 degrees F (2.2 degrees C) above normal, and an area along the border of northeastern Kansas and southeastern Nebraska where average temperatures were 2.0-3.0 degrees F (1.1-1.7 degrees C) below normal. Unlike the majority of this year, the temperatures this month were not record setting; however a small number of locations did break into the top 10 warmest Septembers on record. Lander, Wyoming had its 6th warmest September on record with an average temperature of 63.2 degrees F (17.3 degrees C). In 1990, Lander had its warmest September with an average temperature of 64.8 degrees F (18.2 degrees C) (period of record 1891-2012). Even with some below normal temperatures this month, 2012, as a whole, has continued to be one of the warmest on record for much of the Region. For instance, the average temperature in Topeka, Kansas was 0.5 degrees F (0.3 degrees C) below normal this month, but this year's January 1-September 30 time period still ranked as the warmest. The average temperature in Topeka for that time period was 64.4 degrees F (18.0 degrees C), which easily beat the 1934 record of 62.3 degrees F (16.8 degrees C) (period of record 1887-2012).
  • September was yet another dry month for the majority of the High Plains Region. Precipitation totals which were less than 50 percent of normal were widespread. In addition, a large area of central and northern South Dakota and pockets of North Dakota, Nebraska, and Wyoming received at most 5 percent of normal precipitation. This dearth of precipitation caused many new records to be set this month. Aberdeen, South Dakota had its driest September on record with only 0.01 inches (0 mm) of precipitation which was 2.18 inches (55 mm) below normal. The old record of 0.05 inches (1 mm) was set back in 1979 (period of record 1893-2012). Interestingly there were numerous stations across South Dakota that received no measurable precipitation this month. One of these locations was Pierre, South Dakota which tied with 1893 for its driest September on record (period of record 1893-2012). The dry weather continued to have an impact across the Region. According to the U.S. Army Corps of Engineers, the Missouri River had record low inflows this month of just 0.3 million acre feet. The previous record occurred in 1919 with 0.4 million acre feet (period of record 1898-2012). In addition, water and feed shortages for livestock were common and many producers continued to cull livestock. The dry weather did help with crop dry down and by the end of the month, the corn harvest was well ahead of average in Nebraska and the Dakotas. The only areas of the Region which received above normal precipitation were central and southeastern Colorado, and southwestern and eastern Kansas. These areas had precipitation totals ranging from 110 percent of normal to 300 percent of normal. Denver, Colorado had its 5th wettest September on record with 2.95 inches (75 mm). The record held at 4.67 inches (119 mm), set back in 1961 (period of record 1872-2012). Heavy rainfall in Colorado actually caused problems in areas that had been affected by the wildfires this summer. According to InciWeb, rain caused rock and mud slides in the High Park Fire burn area, west of Fort Collins, Colorado. In addition, numerous trees had also fallen and this combination of rock, mud, and trees caused multiple closures of roads in that area. Luckily, according to The Coloradoan, no property damage or injuries were reported.
  • According to the U.S. Drought Monitor, there have been significant changes in drought conditions over the last month in the High Plains Region. By the end of September, about 99 percent of the Region was under moderate (D1) to exceptional (D4) drought, with nearly 24 percent of the Region in the D4 designation. In contrast, at the end of last month, only 15 percent of the Region was in D4. D4 areas expanded to include most of the state of Nebraska, a small portion of eastern Wyoming, southeastern South Dakota, northeastern Colorado and much of the western and central parts of Kansas. By the end of the month, just over 75 percent of Nebraska was in D4 drought. Extreme drought conditions (D3) also expanded in Nebraska, North Dakota, South Dakota, and Wyoming. In addition, every part of the Region had at least some sort of drought designation or either abnormally dry conditions (D0). About the only improvements occurred in eastern Kansas, where the remnants of Hurricane Isaac helped downgrade drought conditions there. According to the U.S. Seasonal Drought Outlook released September 20th, drought conditions were expected to improve in the far southeastern corner of Kansas and develop in central North Dakota and northern South Dakota. All other areas of drought in the Region were expected to persist through the end of the year.
  • For more information, please go to the High Plains Regional Climate Center Home Page.
  • Southern Region: (Information provided by the Southern Regional Climate Center)
  • September temperatures in the Southern Region were generally at or above normal. In Tennessee and Mississippi, temperatures averaged near normal, with Tennessee averaging 69.00 degrees F (20.56 degrees C) for the month, while Mississippi reported an average temperature of 74.20 degrees F (23.44 degrees C). Elsewhere, temperatures averaged higher than normal, with the warmest areas occurring in Oklahoma and northern Texas. Temperatures in that region ranged from 2 to 4 degrees F (1.11 to 2.22 degrees C) above normal. Texas averaged 76.70 degrees F (24.83 degrees C) for the month. Other state average temperatures include Louisiana with 77.20 degrees F (25.11 degrees C), Oklahoma with 74.10 degrees F (23.39 degrees C), and Arkansas with 73.10 degrees F (22.83 degrees C). Though all state averages rank within the middle two quartiles, Oklahoma and Louisiana are on pace to having one of the warmest years on record. In the case of Oklahoma, the year to date (January to September) average temperature there is 66.89 degrees F (19.38 degrees C). This is their warmest January to September period on record (1895-2012). For Louisiana, it is their second warmest year to date on record (1895-2012). The January to September average for the Louisiana is 71.74 degrees F (22.08 degrees C), second only to the value of 72.11 degrees F (22.28 degrees C), which occurred in 1911. The Southern Region as a whole is also on pace for its warmest year on record. The January to September average for the region is 69.14 degrees F (20.63 degrees C), and it is the warmest January to September period on record (1895-2012).
  • September precipitation in the Southern region varied spatially. Most regions received either anomalously high or anomalously low amounts of precipitation. In Oklahoma, for example, conditions were quite dry in the northeast and in the southeast, with most stations reporting less than half the expected precipitation for the month. This was also the case for the southern tip of Texas and in northwestern Arkansas. Conversely, many areas reported over 150 percent of normal precipitation. This includes most of eastern Tennessee, northern Louisiana, central Texas, and eastern Arkansas. The wettest areas of the region occurred in central Texas and in northwestern Louisiana, where stations reported over twice the normal allotment. In the case of Texas, it was their wettest month in two years. The state reported an average precipitation total of 4.01 inches (101.85 mm), which makes it the twenty-seventh wettest September there on record (1895-2012). It also marks the first time since September of 2010, that the state reported an average precipitation value that was equal to or greater than 4 inches (101.60 mm). Tennessee reported its twelfth wettest September on record with an average precipitation total of 6.02 inches (152.91 mm). Both Louisiana and Arkansas reported their twenty-first wettest September on record (1895-2012), with Louisiana averaging 6.01 inches (152.65 mm), and Arkansas averaging 5.19 inches (131.83 mm). Other state average precipitation totals include Oklahoma with 2.90 inches (73.66 mm), and Mississippi with 4.15 inches (105.41 mm). Over the past three months (July to September), Mississippi has accumulated 19.76 inches (501.90 mm), making it the wettest July to September there on record (1895-2012).
  • Heavy rainfall amounts in the Southern Region has led to some improvements to drought conditions. In Arkansas, the northeastern counties have been improved from extreme and exceptional drought to severe drought conditions. Conditions are also improved for much of western Tennessee. Moderate to severe drought conditions were also scaled back in northern Louisiana and southern Arkansas. Elsewhere, drought conditions did not significantly change. Much of Oklahoma and southern Texas remain in extreme drought or worse, while moderate drought conditions are still prevalent in central and western Texas.
  • Dozens of wind and hail events occurred on September 7, 2012. Most of these occurred in Oklahoma and Arkansas. Baseball-sized hail was reported in Nowata County, Oklahoma, while two hangars were destroyed by heavy wind in Independence County, Arkansas
  • Dozens of hail events occurred in western Oklahoma on September 26, 2012.
  • In Texas, widespread flooding as a result of exceptionally high 24-hour accumulations occurred in Jonestown, San Antonio, and Midland, with further damage from lightning and winds in Lubbock and Montgomery County; hundreds of people lost power as a direct result, and hundreds more required high water rescue (Information Provided by the Texas State Climate Office).
  • Texas rainfall has helped mitigate many of the short-term drought effects, as seen in central Texas, where cotton farmers are expecting a 75% higher yield than last year and ranchers were provided relief as livestock overhead has been increasing due to rising feed prices. Hydrological improvements of these rains are limited, however; while San Angelo is expected 50,000+ acre-feet to be recovered to O. H. Ivie Reservoir, Jonestown's lake and reservoir levels are still so low that their revenues from water-sport related purchases are down and have been put in a budget crunch to the tune of $363,000. Jonestown has had to remove its head librarian and police chief positions and repurpose them to city administrators. Ecological impacts are also still being felt, as Longview's forestry service has gone far above budget removing trees killed by lasting drought conditions. The service has already spent nearly $90,000 on tree removal, with an estimated 301 million dead trees still requiring removal (Information Provided by the Texas State Climate Office).
  • Corpus Christi, already in a large rainfall deficit, saw soil shrinkage damaging building foundations as unseasonably high temperatures evaporated soil moisture. Old building infrastructure in Abilene has been having problems mitigating heat. Outdoorsmen in west Texas suffered heat exhaustion during the warmest days of the month, and wildfires as a result of drying grasses in southeast Texas broke out. By the end of the month, however; temperatures dropped for much of the state and impacts associated with it have slightly subsided (Information Provided by the Texas State Climate Office).
  • For more information, please go to the Southern Regional Climate Center Home Page.
  • Western Region: (Information provided by the Western Regional Climate Center)
  • Continuing this summer's theme of record heat and dry conditions, September 2012 saw above normal temperatures and below normal precipitation for much of the West. Late season monsoon activity over the southern Great Basin and Mojave Desert and a duo of storms hitting south-central Alaska brought locally heavy precipitation, while other locations remained parched.
  • Following its warmest August on record, Reno, Nevada experienced its warmest September as well with a monthly average temperature of 70.7 F (21.5 C). This value narrowly eclipses the previous record of 70.6 F (21.4 C) set in 2011. Reno's record began in 1888. In California's Central Valley, Fresno also saw consecutive August-September record average monthly temperatures. Fresno's temperature this month averaged to 81.3 F (27.4 C), the highest September mean on a record began in 1878. Further south, Needles and Death Valley, California also logged their warmest average September temperatures at 91.3 F (32.9 C) and 96.3 F (35.7 C), respectively.
  • In southern Alaska, cool and wet conditions dominated the month. Two strong storms brought heavy precipitation, cool temperatures, and high winds to the region. An impressive 26.16 in (664.5 mm) of rain fell in Valdez this month, 16.54 in (420.1 mm) above average. This total sets both the September record and the record for wettest calendar month in Valdez. The previous wettest month was 20.59 in (523 mm) in November, 1976; records at Valdez began in 1949. The two storms resulted in widespread flooding throughout south-central Alaska. The Nenana river reached its highest level on record, reducing the Parks Highway to one lane. Sustained winds of 40-50 mph (64-80 kph) were observed around Anchorage, with gusts up to 70-80 mph (112-129 kph). Due to full foliage and moist soil, the strong winds downed trees throughout the region causing power outages, closed roads, and structure damage.
  • The North American monsoon season (June 15-Sept 30) wrapped up this month, with many locations receiving near or above their normal monsoon precipitation totals. Las Vegas, Nevada received 1.18 in (30 mm) on September 11th, the location's wettest September day on record. The downpours resulted in extensive flooding in the Las Vegas area. The month ranks as the 5th wettest in a record that began in 1937. In northern Arizona, Bagdad received 10 in (254 mm) for the monsoon season, 187% of normal for the station. Elsewhere in the region, Prescott and Flagstaff received 76% and 100% of their average Monsoon precipitation. Albuquerque, New Mexico finished the season at 72% of normal. September 2012 was the 5th wettest at Denver, Colorado, with a total of 2.95 in (74.9 mm) of rainfall. It was also the 12th consecutive September with no snowfall in Denver. The other 12-year stretch of no September snowfall occurred from 1914-1926.
  • Precipitation was lacking elsewhere in the West, with many Pacific Northwest locations noting their driest Septembers on record and extended periods with no measurable precipitation. Both Billings and Missoula, Montana received only trace precipitation, their driest Septembers on records beginning in 1934 and 1893, respectively. At Missoula, it was only the second time in the station's history that any month in the year received no measurable precipitation. Sheridan, Wyoming also recorded only trace precipitation in September tying the driest on record. Beginning the 11th of August, 51 consecutive days passed at Sheridan without measurable precipitation, the longest dry period in a record beginning in 1920. In Washington, Spokane, Bellingham, and Olympia all set or tied their driest September on record. Dry conditions also dominated Hawaii, where Lihue, Kauai, received only 35% of its normal September rainfall. Precipitation at Lihue has been below average nine of eleven months of the current water year.
  • Northwest Fires: With dry fuels, high temperatures, and low relative humidity prevailing throughout the month, many large wildfires ignited or grew throughout September. Smoke from the fires lead to poor air quality in eastern Washington and Oregon, northern Idaho, western Montana, and Northern California. One of the largest, at 339,110 acres (137,233 hectares) by month's end, was the Mustang Fire on the Idaho-Montana border. The North Pass Fire, 10 miles northeast of Covelo, CA has burned 41,983 acres (16,990 hectares) and consumed 26 structures. The national average of large fire events for 2012 remains at 77% of the 10-year average, while acreage burned this year is at 129% of the recent average.
  • September 11: Las Vegas area flooding: A band of thunderstorms brought heavy precipitation to the Las Vegas Valley and surrounding areas. Flooding closed roads, swamped cars, damaged homes and businesses, and resulted in one fatality. Flood damages in Las Vegas are estimated at $75 million. Southwest Utah, northeastern Arizona, and southeastern California also experienced heavy precipitation and damaging flash floods.
  • For more information, please go to the Western Regional Climate Center Home Page.

See NCDC's Monthly Records web-page for weather and climate records for the most recent month. For additional national, regional, and statewide data and graphics from 1895-present, for any period, please visit the Climate at a Glance page.


PLEASE NOTE: All of the temperature and precipitation ranks and values are based on preliminary data. The ranks will change when the final data are processed, but will not be replaced on these pages. Graphics based on final data are provided on the Temperature and Precipitation Maps page and the Climate at a Glance page as they become available.

Global Analysis

Contents of this Section:


September 2012 Selected Climate Anomalies and Events MapSeptember 2012 Selected Climate
Anomalies and Events Map

Global Highlights

  • The average combined global land and ocean surface temperature for September 2012 tied with 2005 as the warmest September on record, at 0.67°C (1.21°F) above the 20th century average of 15.0°C (59.0°F). Records began in 1880.

  • The globally-averaged land surface temperature for September 2012 was the third warmest September on record, at 1.02°C (1.84°F) above average. The globally-averaged ocean surface temperature tied with 1997 as the second warmest September on record, at 0.54°C (0.97°F) above average.

  • The average combined global land and ocean surface temperature for January–September 2012 was the eighth warmest such period on record, at 0.57°C (1.03°F) above the 20th century average.


==global-temps-errata==

Introduction

Temperature anomalies and percentiles are shown on the gridded maps below. The anomaly map on the left is a product of a merged land surface temperature (Global Historical Climatology Network, GHCN) and sea surface temperature (ERSST.v3b) anomaly analysis developed by Smith et al. (2008). Temperature anomalies for land and ocean are analyzed separately and then merged to form the global analysis. For more information, please visit NCDC's Global Surface Temperature Anomalies page. The September 2012 Global State of the Climate report introduces percentile maps that complement the information provided by the anomaly maps. These new maps on the right provide additional information by placing the temperature anomaly observed for a specific place and time period into historical perspective, showing how the most current month, season or year compares with the past.

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Temperatures

In the atmosphere, 500-millibar height pressure anomalies correlate well with temperatures at the Earth's surface. The average position of the upper-level ridges of high pressure and troughs of low pressure—depicted by positive and negative 500-millibar height anomalies on the September 2012 height and anomaly mapSeptember 2012 map—is generally reflected by areas of positive and negative temperature anomalies at the surface, respectively.

September

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Global Temperature Percentile Maps

Global anomaly maps are an essential tool when describing the current state of the climate across the globe. Temperature anomaly maps tell us whether the temperature observed for a specific place and time period (for example, month, season, or year) was warmer or cooler than a reference value, which is usually a 30-year average, and by how much.

The August 2012 Global State of the Climate report introduces percentile maps that complement the information provided by the anomaly maps. These new maps provide additional information by placing the temperature anomaly observed for a specific place and time period into historical perspective, showing how the most current month, season or year compares with the past.

Temperature Climatological Ranking

In order to place the month, season, or year into historical perspective, each grid point's temperature values for the time period of interest (for example all August values from 1880 to 2012) are sorted from warmest to coolest, with ranks assigned to each value. The numeric rank represents the position of that particular value throughout the historical record. The length of record increases with each year. It is important to note that each grid point's period of record may vary, but all grid points displayed in the map have a minimum of 80 years of data. For the global temperature anomaly record, the data does extend back to 1880. But not all grid points have data from 1880 to present. Considering a grid point with a period of record of 133 years, a value of "1" in the temperature record refers to record warmest, while a value of "133" refers to record coldest.

The Warmer than Average, Near Average, and Cooler than Average shadings on the temperature percentile maps represent the bottom, middle, and upper tercile (or three equal portions) of the sorted values or distribution, respectively. Much Warmer than Average and Much Cooler than Average, refer to the lowest and uppermost decile (top or bottom 10 percent) of the distribution, respectively. For a 133-year period, Warmer than Average (Cooler than Average) would represent one of the 44 warmest (coolest) such periods on record. However, if the value ranked among the 13 warmest (coolest) on record, that value would be classified as Much Warmer than Average (Much Cooler than Average). Near Average would represent an average temperature value that was in the middle third (rank of 45 to 89) on record.

More about climate monitoring…

The average global temperature across land and ocean surfaces during September was 0.67°C (1.21°F) above the long-term 20th century average. This temperature ties with 2005 as the record warmest September in the 133-year period of record. The Northern Hemisphere tied with 2009 as second warmest on record, behind 2005. The Southern Hemisphere also ranked second warmest on record, behind 1997. It was also the highest departure from average for any month in the Southern Hemisphere since May 2010.

The average global land surface temperature was the third highest for September on record, behind 2009 (highest) and 2005 (second highest), with widespread warmth around the globe. It was the third warmest September over land in the Northern Hemisphere and fourth warmest in the Southern Hemisphere. In the higher northern latitudes, parts of east central Russia observed record warmth, as did parts of Venezuela, French Guiana, and northern Brazil closer to the tropics. Nearly all of South America was much warmer than average as were western Australia and central to eastern Europe. Far eastern Russia, a few regions in southern Africa, and parts of China were cooler than average.

Select national information is highlighted below:
  • Following the second warmest summer (June–August) for Hungary since national records began in 1900, monthly temperatures remained above average across the entire country during September, ranging from about 1.0°–3.5°C (1.8°–6.3°F) above the 1971–2000 average, according to the country's national meteorological service, Országos Meteorológiai Szolgálat.

  • Australia experienced its third warmest September since records began in 1950, with the nationally-averaged maximum temperature 1.94°C (3.49°F) above the 1961–1990 average. The minimum temperature was also above average but not quite as extreme as the maximum, at 0.42°C (0.76°F) above the long-term average.

  • According to Argentina's national meterological service, Servicio Meteorológico Nacional, the monthly-averaged daily, maximum, and minimum temperatures were all above normal across Argentina, particularly in the central and northern regions of the country. Record high September minimum temperatures were observed across parts of the midwest.

  • As indicated in the land and ocean temperature percentiles map above, Japan observed record warmth during September. According to the Japan Meteorological Agency, the greatest warmth was observed across northern Japan (regions of Hokkaido and Tohuko), which was 3.7°C (6.7°F) above average. It was below average across Okinawa, which had been impacted by Super Typhoons Sanba (middle of the month) and Jelawat (end of the month).

  • With warm temperatures during the first half of the month transitioning to cooler temperatures brought about by a strong low pressure system, the average September temperature across the United Kingdom was 0.7°C (1.3°F) below the 1981–2010 average. This marks the coolest September for the region since 1994, according to the UK Met Ofiice.

The globally-averaged ocean temperature tied with 1997 as second highest for September, behind 2003, at 0.55°C (0.99°F) above the long-term average. This was also the highest departure from average for any month since May 2010. Much of the anomalous warmth was generated in the central western Pacific and the northeastern and equatorial North Atlantic Oceans, all of which observed record warmth in some areas. Most of the Indian Ocean was also warmer than average, with some record warmth observed off the southwestern Australian coast. Cooler-than-average temperatures were present in regions of the northeastern and southeastern Pacific Ocean. In the central and eastern equatorial Pacific, borderline ENSO-neutral / weak El Niño conditions were present as surface temperatures remained above average. According to NOAA's Climate Prediction Center, these conditions are likely to continue throughout the Northern Hemisphere winter 2012/13, with possible strengthening to warm-phase El Niño conditions during the next few months. In addition to influencing seasonal climate outcomes in the United States, El Niño is often, but not always, associated with global temperatures that are higher than the general trend.

September Anomaly Rank
(out of 133 years)
Records
°C °F Year(s) °C °F
Global
Land +1.02 ± 0.25 +1.84 ± 0.45 Warmest 3rd 2009 +1.06 +1.91
Coolest 131st 1912 -0.79 -1.42
Ocean +0.55 ± 0.04 +0.99 ± 0.07 Warmest 2nd 2003 +0.58 +1.04
Coolest 132nd 1912 -0.46 -0.83
Ties: 1997
Land and Ocean +0.67 ± 0.11 +1.21 ± 0.20 Warmest 1st 2005, 2012 +0.67 +1.21
Coolest 133rd 1912 -0.55 -0.99
Ties: 2005
Northern Hemisphere
Land +1.04 ± 0.26 +1.87 ± 0.47 Warmest 3rd 2005 +1.18 +2.12
Coolest 131st 1912 -0.93 -1.67
Ocean +0.61 ± 0.04 +1.10 ± 0.07 Warmest 4th 2003 +0.67 +1.21
Coolest 130th 1912 -0.56 -1.01
Land and Ocean +0.77 ± 0.15 +1.39 ± 0.27 Warmest 2nd 2005 +0.83 +1.49
Coolest 132nd 1912 -0.70 -1.26
Southern Hemisphere
Land +0.97 ± 0.21 +1.75 ± 0.38 Warmest 3rd 2007 +1.13 +2.03
Coolest 131st 1894 -0.78 -1.40
Ties: 2011
Ocean +0.51 ± 0.05 +0.92 ± 0.09 Warmest 3rd 1997 +0.57 +1.03
Coolest 131st 1911 -0.52 -0.94
Ties: 2003
Land and Ocean +0.58 ± 0.09 +1.04 ± 0.16 Warmest 2nd 1997 +0.66 +1.19
Coolest 132nd 1911 -0.56 -1.01
Year-to-date (January–September)

The year-to-date globally-averaged temperature anomaly across land and oceans combined has been steadily increasing since February as a cold phase La Niña (at least 0.5°C / 0.9°F below the 1981–2010 average) in the equatorial Pacific Ocean at the beginning of the year transitioned into ENSO-neutral conditions that bordered the threshold for warm El Niño conditions (at least 0.5°C / 0.9°F above average) by August. The global land and ocean temperature for the first nine months (January–September) of 2012 was 0.57°C (1.03°F) above the 20th century average, ranking as the eighth warmest since records began in 1880. If this warmth continues through the end of the year, 2012 will surpass 2011 as the warmest La Niña year since the Climate Predition Center began monitoring ENSO conditions in 1950.

The January–September global land surface temperature ranked as the sixth warmest such period on record. In the Northern Hemisphere, where the majority of Earth's land masses are located, the year-to-date temperature was the fourth warmest on record, largely attributed to monthly record warmth during April, May, June, and July. Across the globe, temperatures were much warmer than average across most of the Americas, southern and eastern Africa, southern and southeastern Asia, east central Russia, and most of central and eastern Europe. Record warmth was observed across the eastern two-thirds of the United States and south central Canada.

The global ocean temperature for the year-to-date was the 10th warmest such period on record, with much warmer than average temperatures present across much of the North Atlantic, Indian, and western Pacific oceans. Cooler-than-average temperatures spanned much of the northeastern and east central Pacific Ocean.

January–September Anomaly Rank
(out of 133 years)
Records
°C °F Year(s) °C °F
Global
Land +0.95 ± 0.22 +1.71 ± 0.40 Warmest 6th 2007 +1.10 +1.98
Coolest 128th 1893 -0.67 -1.21
Ocean +0.43 ± 0.04 +0.77 ± 0.07 Warmest 10th 1998 +0.56 +1.01
Coolest 124th 1911 -0.49 -0.88
Ties: 2007
Land and Ocean +0.57 ± 0.10 +1.03 ± 0.18 Warmest 8th 1998, 2010 +0.68 +1.22
Coolest 126th 1911 -0.50 -0.90
Northern Hemisphere
Land +1.06 ± 0.27 +1.91 ± 0.49 Warmest 4th 2007 +1.24 +2.23
Coolest 130th 1884, 1893 -0.75 -1.35
Ocean +0.44 ± 0.05 +0.79 ± 0.09 Warmest 10th 2005, 2010 +0.56 +1.01
Coolest 124th 1910, 1913 -0.48 -0.86
Land and Ocean +0.67 ± 0.15 +1.21 ± 0.27 Warmest 6th 2010 +0.77 +1.39
Coolest 128th 1904, 1913 -0.51 -0.92
Southern Hemisphere
Land +0.67 ± 0.14 +1.21 ± 0.25 Warmest 8th 2005 +0.93 +1.67
Coolest 126th 1917 -0.73 -1.31
Ties: 2011
Ocean +0.44 ± 0.04 +0.79 ± 0.07 Warmest 10th 1998 +0.58 +1.04
Coolest 124th 1911 -0.52 -0.94
Ties: 1997, 2011
Land and Ocean +0.48 ± 0.07 +0.86 ± 0.13 Warmest 10th 1998 +0.64 +1.15
Coolest 124th 1911 -0.54 -0.97
Ties: 2007

The most current data September be accessed via the Global Surface Temperature Anomalies page.

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Images of sea surface temperature conditions are available for all weeks during 2012 from the weekly SST page.


Precipitation

The maps below represent precipitation percent of normal (left) and precipitation percentiles (right) based on the GHCN dataset of land surface stations using a base period of 1961–1990. As is typical, precipitation anomalies during September 2012 varied significantly around the world.

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Did You Know?

Global Precipitation Percentile Maps

Global anomaly maps are an essential tool when describing the current state of the climate across the globe. Precipitation anomaly maps tell us whether the precipitation observed for a specific place and time period (for example, month, season, or year) was drier or wetter than a reference value, which is usually a 30-year average, and by how much.

The August 2012 Global State of the Climate report introduces percentile maps that complement the information provided by the anomaly maps. These new maps provide additional information by placing the precipitation anomaly observed for a specific place and time period into historical perspective, showing how the most current month, season or year compares with the past.

Precipitation Climatological Ranking

In order to place the month, season, or year into historical perspective, each grid point's precipitation values for the time period of interest (for example all August values from 1900 to 2012) are sorted from driest to wettest, with ranks assigned to each value. The numeric rank represents the position of that particular value throughout the historical record. The length of record increases with each year. It is important to note that each grid point's period of record may vary, but all grid points displayed in the map have a minimum of 80 years of data. For example, considering a grid point with a period of record of 113 years, a value of "1" in the precipitation record refers to record driest, while a value of "113" refers to record wettest.

The Drier than Average, Near Average, and Wetter than Average shadings on the precipitation percentile maps represent the bottom, middle, and upper tercile (or three equal portions) of the sorted values or distribution, respectively. Much Drier than Average and Much Wetter than Average, refer to the lowest and uppermost decile (top or bottom 10 percent) of the distribution, respectively. For a 113-year period, Drier than Average (Wetter than Average) would represent one of the 38 driest (wettest) such periods on record. However, if the value ranked among the 11 driest (wettest) on record, that value would be classified as Much Drier than Average (Much Wetter than Average). Near Average would represent an average precipitation value that was in the middle third (rank of 39 to 75) on record.

More about climate monitoring…

  • Seasonal rainfall in western and central Africa was unusually heavy during September, leading to flood conditions that stretched from Senegal eastward to Chad.

  • The South Asian monsoon season in India starts around the beginning of June and lasts into October. The monsoon stalled over northwestern India before beginning its annual withdrawal, bringing excessive rainfall to most of the region during the month of September. The heavy rainfall brought seasonal precipitation totals to within the normal range and alleviated drought conditions for much, but not all, of the country. For this year's monsoon period to date (1 June – 30 September), most provinces in India reported rainfall in the normal range (81–119 percent of average), with the exception of several provinces in the south and east and a few in the north that observed deficient rainfall (61–80 percent of average). For the period June–September, India as a whole experienced rainfall that was 92 percent of average, within the normal range, according to the India Meteorological Department.

  • Several countries in eastern Europe, including Romania, Hungary, Bulgaria, and Poland, experienced drought during September. It was one of worst droughts for Hungary in two decades.

  • During mid-September, Super Typhoon Sanba—the year's first category 5 storm among all tropical cyclone basins—brought locally heavy rainfall to Okinawa Island, Japan, parts of the Philippines, including the capital city of Manilla, and both North and South Korea. Super Typhoon Jelawat—the year's second category 5 storm—also impacted part of the eastern Philippines and parts of Japan, including Okinawa and Tokyo.

Additional details on flooding and drought events around the world can also be found on the September 2012 Global Hazards page.

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References

Peterson, T.C. and R.S. Vose, 1997: An Overview of the Global Historical Climatology Network Database. Bull. Amer. Meteorol. Soc., 78, 2837-2849.

Quayle, R.G., T.C. Peterson, A.N. Basist, and C. S. Godfrey, 1999: An operational near-real-time global temperature index. Geophys. Res. Lett., 26, 333-335.

Smith, T.M., and R.W. Reynolds (2005), A global merged land air and sea surface temperature reconstruction based on historical observations (1880-1997), J. Clim., 18, 2021-2036.

Smith, et al (2008), Improvements to NOAA's Historical Merged Land-Ocean Surface Temperature Analysis (1880-2006), J. Climate., 21, 2283-2293.

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Global Hazards

Please note: Material provided in this report is chosen subjectively and included at the discretion of the National Climatic Data Center (NCDC). The ability to report on a given event is limited by the amount of information available to NCDC at the time of publication. Inclusion of a particular event does not constitute a greater importance in comparison with an event that has not been incorporated into the discussion. Data included in this report are preliminary unless otherwise stated. Links to supporting information are valid at the time of publication, but they are not maintained or changed after publication.


Updated 31 Oct 2012


September 2012Bushfires sparked across dry Australia outback. read more September 2012Deadly wildfires blazed in Portugal and Spain. read more September 2012Monsoons flooded central African nations, parts of Pakistan and India. read more September 6th–8thSevere weather battered central and eastern U.S. read more September 2012Super typhoons walloped Japan. read more September 2012Strong storms inundated southern Alaska. read more September 2012Antarctic sea ice reached an all-time maximum extent. read more September 2012Desert locusts invaded northern Africa. read more



Drought conditions

Australian Burn Scars on 18 September 2012 on 18 September 2012
Australian Burn Scars
on 18 September 2012
Source: NASA

Early spring continued to foster dry conditions in the Southern Hemisphere. Central Australia, which typically receives very little rainfall during its May to September dry season, experienced extreme dryness during the month. On September 29th, a light rain of 3 mm (one-eighth inch) ended a streak of 157 consecutive days without precipitation at Alice Springs Airport. The streak was the longest dry spell at the location since records began in 1940. A fire vortex that spun up to 30 m (100 ft) high erupted during a wildfire near Alice Springs on September 11th.

In eastern Australia, dangerous wildfire conditions existed in New South Wales (NSW) where up to 50 grass, scrub, and bushfires flared in early September. Strong northwest winds fanned a grass fire near Berridale which destroyed a historic homestead and scorched almost 500 acres in the Snowy Mountains. Water-dropping aircraft assisted in containment efforts on another wildfire in the Budderoo National Park. Sydney experienced high temperatures of 31°C (88°F) during late September, where hot and dry conditions in NSW were cited as the worst in nearly 40 years, according to media reports.


North American Drought Monitor Map of 30 September 2012
North American Drought Monitor
Map of 30 September 2012
Source: NOAA NCDC

In the Northern Hemisphere, persistent drought and warmth in the U.S. and Canada fueled wildfires through beetle-killed forests. Over 64 percent of the contiguous U.S. was experiencing moderate-to-exceptional drought. Please visit the U.S. Drought Monitor report and NOAA's Wildfires page for additional information. Year-to-date acres burned through September in the U.S. was 8.8 million acres (48,258 fires), and 4.7 million acres in Canada (7,288 fires). In British Columbia, four homes were destroyed by flames and over 1,500 people were evacuated on September 9th, according to media reports. The arid Canadian region of Okanagan that is ideal for the cultivation of vineyards is prone to wildfires in dry seasons. The White Spruce Creek wildfire threatened oil and gas facilities late in the month and prompted local evacuations, while blazing over 54,000 acres to the east of Fort Nelson.

Across Europe, wildfires continued to take a toll as hot temperatures and gusty winds exacerbated the fire behavior. According to media reports, fires in Portugal destroyed over 173,000 acres between January and August and claimed the lives of two firefighters. About 20 bushfires blazed in the drought-stricken country in early September and threatened up to 3,000 people. In western Portugal, one person perished in the flames, which destroyed two homes and a factory, and caused disruption of road and rail services between Pombal and Fatima.


Russian Wildfires on 23 September 2012
Russian Wildfires
on 23 September 2012
Source: NASA

In Spain, more than 378,000 acres burned between January and August 2012, which was triple the amount for the same period in 2011 — and was the highest amount burned in a decade, according to media accounts. In early September, one fatality and five injuries in southern Spain resulted from an intense forest fire in the Costa del Sol region, which charred over 12,000 acres and forced the evacuation of nearly 4,000 people near Ojen. In Russia, over 74 million acres burned between January and August, mostly in the eastern and central Siberian taiga. Scientists determined the Russian wildfires emitted more carbon monoxide in 2012 (48 teragrams) than in any year since 2003 (72 teragrams).

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Heavy rainfall and flooding

Heavy rainfall in west and central Africa resulted in widespread flooding that impacted more than 3 million people since early July. Heavy rains in late August damaged more than 11,400 homes in Senegal and displaced nearly 287,000 of its residents.


Flooding of Nigerian Rivers on 13 October 2012
Flooding of Nigerian Rivers
on 13 October 2012
Source: NASA Earth Observatory

Torrential rains produced deadly flooding in Nigeria and necessitated the release of water from the Jebba and Kainji hydropower dams on the Niger River in late September to prevent their collapse. Emergency officials estimated over 35,000 people in central Nigeria were displaced from their homes during the month, with many villagers being rescued by boat from rooftops or trees. Flooding in the Kogi state, which occurred at the confluence of the Niger and Benue rivers, was deemed as the worst in 50 years. Flood waters carried hippopotamuses, crocodiles, and snakes into residential areas. Humanitarian relief organizations sought to provide food and shelter for the country's large number of Internally Displaced Persons (IDPs) in the Rivers State, whose plights were compounded by the deluges. Flooding threatened the cocoa-producing farmlands in the southwestern region of Nigeria, where 2 m (7 ft) of water submerged roads leading to the commercial center near Lagos. According to media accounts, at least 148 deaths resulted from flooding within the north and central Nigerian states since early July, while the heavy rains displaced over 620,000 Nigerians, close to 4,000 homes, inundated more than 370,000 acres of farmland, and induced at least 135 cases of cholera. As of mid-October, the number of fatalities across the country exceeded 430 since July, with nearly 550,000 homes lost, and more than 1.3 million Nigerians displaced due to the floods.

In the Republic of Niger, floods resulted in 88 deaths, the loss of over 24,000 homes, and affected over 511,000 people during September. Morocco provided nearly 45 metric tons in foodstuff, as part of its humanitarian aid to Niger in early October. In Chad, flooding destroyed over 94,000 homes in September, while 630,000 acres of cropland and nearly 520,000 people were adversely impacted. Heavy rains in mid-September caused breaching of the Lagdo Dam and swelled the Benue River in northern Cameroon, which resulted in up to 40 deaths, nearly 3,000 injuries, and impacted more than 26,000 residents, according to media reports. Morroco provided humanitarian aid to Cameroon during September.


Central Pakistan Flooding on 13 September 2012
Central Pakistan Flooding
on 13 September 2012
Source: NASA Earth Observatory

Monsoon rains triggered flash floods and hill torrents across central Pakistan in early September, resulting in widespread loss of life, livelihoods, and infrastructure. Over 4.8 million people were affected, primarily within the Balochistan, Punjab, and Sindh provinces. Extensive humanitarian efforts to provide food rations and medicines were coordinated by World Health Organization partners. Critical dietary staples included fortified wheat flour and vegetable oil, iodized salt, high-energy biscuits and supplements for infants. Standing water and damages to roadways hampered relief activities, which forced the distribution efforts to be conducted by boats. Supplying nutritional safe drinking water and sanitation services were priority needs in the flood-afflicted areas. Nearly 350,000 people sought refuge in over 500 relief camps. More than 402,000 homes and 1.1 million acres of crops were damaged, while over 9,600 cattle perished.


Northeast India Flooding on 25 September 2012
Northeast India Flooding
on 25 September 2012
Source: NASA Earth Observatory

Heavy rains resulted in the flooding of the Brahmaputra River in northeast India during September. The number of displaced people neared 1.8 million, according to media reports. Twenty-one bodies were recovered in the state of Sikkim. At least 13 fatalities occurred in the state of Assam where flooding struck for the third time in 2012. Helicopters dropped provisions of rice, water, biscuits, and baby food to marooned flood victims, as many sought shelter within the estimated 3,000 temporary relief camps. Flooding inundated the 106-acre Kaziranga National Park, which is deemed as a United Nations Educational, Scientific, and Cultural Organization (UNESCO) World Heritage site. The Park is a sanctuary for the world's largest population of one-horned rhinoceroses as well as for numerous tigers, elephants, panthers, bears, and birds.

Flooding along the eastern Canadian coast at mid-month caused damage to homes and roads, according to media accounts. Heavy precipitation of up to 75 mm (2.95 inches) fell in central Nova Scotia on September 10, leaving some homes submerged in close to 1.5 m (4.9 ft) of water. Washed out roadways stranded at least 135 residents near Shubenacadie while some Truro residents were rescued by canoe.

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Severe Storms

A cold front passage across southern Australia in early September produced blustery winds with gusts up to 100 kph (62 mph) in eastern New South Wales, Tasmania, and Victoria and blizzard conditions in the Alpine areas. Damage occurred to roofs as the winds downed trees and power lines, resulting in over 600 emergency calls for assistance by residents.

Nine fatalities resulted in the wake of strong winds of up to 140 kph (87 mph) and heavy rains across central South America on September 19th, according to media reports. In Paraguay, five people died and over 80 others were injured in storm-related incidents, while at least 5,000 homes were destroyed. In Bolivia, two deaths occurred during flooding in the Santa Cruz region. In Uruguay, flooding claimed two lives and forced over 500 residents to evacuate their homes, and over 300 fallen trees led to power outages for 140,000 homes. The ferry service between Uruguay and Argentina was disrupted. Strong winds and rain in Buenos Aires caused evacuation of at least 25 people, power outages, and numerous traffic accidents. Earlier in the month, heavy rains in Buenos Aires produced extensive flooding which ruined over 8.6 million acres of barley and wheat crops, and losses of newborn calves through drowning.


U.S. Storm Reports for 07 September 2012
U.S. Storm Reports
for 07 September 2012
Source: NOAA Storm Prediction Center

In the U.S., a cold front passage through the Mid-Mississippi Valley to the East Coast resulted in over 900 severe weather reports during September 6th–8th, primarily for wind events. Powerful thunderstorms with hail and gusty winds rolled through central Iowa on September 6th. Four fatalities occurred in Oklahoma as a result of the storms on September 7th. Across Missouri, power poles snapped during strong winds with hail leaving residents without utilities, according to media accounts. Strong winds peaking near 128 kph (80 mph) destroyed three airplane hangars and damaged three airplanes at an Arkansas airport, while falling trees damaged two homes and three cars and up to 71,000 Arkansans lost power. A tornado, which briefly hit in southwestern Ohio, damaged several homes and a barn. In New York, two tornadoes touched down on Long Island on September 8th causing minor structural damage to homes and buildings in Queens, while overturning cars in Brooklyn. Damages from winds occurred along nearly 450 km (300 mi) between Maryland and Connecticut. In Virginia, power outages affected nearly 65,000 residents. Twelve injuries occurred during an evacuation of the Prince George's County Fair in Maryland. Later in the month, two tornadoes struck in eastern North Carolina on September 18th where heavy rain flooded roads and downed power lines. Severe storms in southwestern Illinois on September 25th produced hail stones exceeding 5 cm (2 inches) in diameter and dumped as much as 152 mm (6 inches) of rainfall which resulted in flash floods. At least six tornadoes were reported in the state.

Torrential rains in southern Spain on September 28th resulted in flash flooding, which claimed at least 10 lives and forced evacuation of 600 residents, according to media reports. Thirty-five fairground workers in the town of Gandia sustained injuries when a tornado toppled a ferris wheel during violent thunderstorms. Up to 245 mm (9.6 inches) of precipitation inundated the Murcia region, particularly the provinces of Mãlage and Almeria, where the rains washed out bridges and roads, overturned cars, and disrupted rail services. Farmland was damaged and numerous livestock (pigs, horses, donkeys, and hens) perished.

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Extratropical Cyclones

Susitna River Flooding in Alaska on 30 Sep 2012
Susitna River Flooding
in Alaska on 30 Sep 2012
Source: NASA Earth Observatory

In southern Alaska, heavy rains in excess of 76 mm (3 inches) in the Susitna Valley and Talkeetna Mountains resulted in flooding of small rivers and creeks on September 16th. More rains and strong winds on September 19th produced severe flooding and power outages for 2,500 residents in the Matanuska-Susitna Borough. A levee along the Montana Creek was breached and reinforced with truckloads of rock. Residents of the Willow Creek area were evacuated. At least 10 persons were rescued from a flash flood near Wasilla where water levels approached nearly 1.8 m (6 ft). A 152-meter (500-foot) section of the Alaska Railroad along Gold Creek was washed out and prevented freight service by trains to Fairbanks. The Town of Talkeetna was evacuated on September 21st, as the Talkeetna River crested at 5.2 m (16.9 ft), which was second to its record high level of 5.3 m (17.4 ft), according to media reports. Nearby the Susitna River flooded. At least 60 roads and 820 residences were damaged of which 14 homes were destroyed. Flood waters began to slowly recede by the morning of September 22nd.


Extratropical Cyclone off southern Alaska coast on 26 Sep 2012
Extratropical Cyclone off southern
Alaska coast on 26 Sep 2012
Source: NASA Earth Observatory

One fatality was presumed as a man was swept into Butte Creek while attempting to cross on September 24th, where flooding on the Denali Highway stranded a group of nearly 70 hunters. Within days another powerful extratropical cyclone developed off the Alaskan coast, but positioned to lessen the effects of its strong winds and rain over the south-central region. Following a rapid intensification, the storm's central pressure dropped to a minimum of near 956 mb. Coastal areas near Seward received up to 152 mm (6 inches) in additional precipitation, according to media reports. In Valdez, rain fell on 27 of 30 days during September for a total of 664.5 mm (26.16 inches), which was not only the highest amount for September, but also for any month at the location in records since 1949. The previous wettest month was November 1976 when 522.9 mm (20.59 inches) was recorded. The previous September record of 423.9 mm (16.69 inches) was set in 1981.

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Tropical Cyclones

Two tropical cyclones developed off Africa's west coast during September, each reached hurricane strength. Hurricane Michael (Sep 3th–11th), which was the first Atlantic Basin storm to attain Category 3 strength in 2012, stayed entirely over ocean, as did the meandering Hurricane Nadine (Sep 11th–Oct 4th). Nadine earned the distinction as the second-longest Atlantic Tropical Storm on record with 21.25 days (ties Ginger of 1971). Please visit NOAA's Hurricanes and Tropical Storms page for detailed information.


Eastern Pacific Tropical Cyclones off Baja California on 16 Sep 2012
Eastern Pacific Tropical Cyclones
off Baja California on 16 Sep 2012
Source: NASA Earth Observatory

In the Eastern Pacific, two hurricanes and three tropical storms originated during the month. Tropical Storms John (Sep 2nd–4th), Kristy (Sep 9th–17th), and Hurricane Miriam (Sep 22nd–28th) followed similar tracks along the west coast of Mexico. Likewise, Hurricane Lane (Sep 15th–19th) remained completely at sea. Tropical Storm Norman (Sep 28th–30th) made landfall near Topolobampo, Mexico, and claimed one fatality. A shrimp trawler ran aground at the port of Mazatlãn and one of the eight crewmen was injured, according to media accounts. About 400 vessels sought safety from Norman's strong winds and large waves within the harbors along the Sea of Cortez. The southwestern U.S. also received heavy rainfall associated with Norman in excess of 102 mm (4 inches).


Typhoon Sanba near Philippines on 13 Sep 2012
Typhoon Sanba near Philippines
on 13 Sep 2012
Source: NASA Earth Observatory

Six tropical cyclones formed in the Western Pacific during September of which two storms developed into deadly typhoons. Typhoon Sanba (a.k.a. Karen; Sep 9th–18th), which originated west of the Philippines, reached Category 5 strength by September 13th before making an initial landfall on September 16th in Okinawa, Japan, then another landfall in South Korea on September 17th. Sanba became the fourth typhoon to strike the Korean Peninsula in a single year — an event that has not occurred for 50 years, according to media reports. Over 200 mm (7.8 inches) of precipitation fell in southern regions of the country prompting landslides in the Gyeongsang province. Six fatalities resulted, more than 1,100 Korean residents were forced to evacuate, while over 67,000 Japanese and 382,000 Korean households lost power due to the storm. Extensive flooding occurred in the Philippines, western Japan, northeastern China, and Far East Russia in association with the storm's passage. The Russian city of Vladivostok received up to 107 mm (4.2 inches) of precipitation in 24 hours, which flooded roads and parts of the local airport.


Typhoon Jelawat over Philippine Sea on 25 Sep 2012
Typhoon Jelawat over
Philippine Sea on 25 Sep 2012
Source: NASA

Typhoon Jelawat (a.k.a. Lawin; Sep 20th–Oct 1st), which originated east of Guam and veered northeast of Taiwan to make two landfalls in Japan, resulted in seven deaths and at least 180 injuries, according to media reports. The powerful storm was the second to hit the region in two weeks and the 17th typhoon to strike Japan in 2012. Heavy rains and strong winds resulted in widespread power outages and disrupted transportation services. Jelawat punched Okinawa with nearly 185 kph (115 mph) winds on September 29th, accompanied by gusts to nearly 232 kph (144 mph) which exerted force to overturn vehicles. Jelawat arrived west of Tokyo with winds of 126 kph (78 mph) on September 30th. Precautionary evacuations of over 50,000 residents along rivers were mandated in the city of Nagoya.

After their respective originations near Guam, Tropical Storms Ewiniar (Sep 23rd–30th) and Maliksi (Sep 29th–Oct 4th) followed similar northward tracks to the east of Japan, bringing heavy rains and storm surges along Honshu. Tropical Storm Gaemi (a.k.a. Marce; Sep 29th–Oct 7th ) formed in the South China Sea and initially moved toward the Philippines before looping back to make landfall in central Vietnam. One fatality resulted when the storm's strong winds and waves capsized a motor bancas transporting three Filipino fishermen. Flooding from storm surge in the Philippines resulted in emergency assistance to nearly 300 residents and damage to over 50 homes. The storm brought heavy rains and flooding to parts of Vietnam, Laos, Cambodia, and Thailand. The strong winds of the storm posed a threat to Vietnam's coffee industry whose harvest was near, as the young cherries, which contain the coffee plant's beans, could be dropped prematurely. Reservoirs in Thailand were lowered in advance of the torrential rains as a safety measure.

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Polar Events and Sea Ice
Fragmented Arctic sea ice on 13 September 2012
Fragmented Arctic sea ice
on 13 September 2012
Source: NASA Earth Observatory

During September, the Arctic sea ice retreated to an all-time minimum extent since satellite records began in 1979, with an average extent of 1.39 million square miles. On September 16th, the lowest daily extent was 1.32 million square miles. The amount of melt during the season was 4.57 million square miles, which would be about the size of the entire U.S. and Mexico combined. The Arctic region is the fastest-warming region on the planet and its September sea ice extent has declined by 13 percent per decade over the last 33 years. Scientists concluded that the shrinking Arctic ice may have contributed to extreme effects on weather in Greenland, the U.S., and western Europe. For a more thorough discussion of sea ice extent, please see NOAA's Press Release. Reduction in Arctic ice threatens the habitats of Arctic wildlife including polar bears and walruses. Initial oil drilling operations were hindered by an enormous chunk of sea ice adrift in the Chukchi Sea. The ice — spanning 360 square miles across and up to 25 m (82 ft) in thickness — forced relocation of the Royal Dutch Shell drillship on September 10th.

Antarctic sea ice extent during September 2012
Antarctic sea ice extent
during September 2012
Source: NASA

Conversely, at the opposite pole, Antarctic sea ice reached its all-time highest daily extent on record with a maximum extent of 7.51 million square miles on September 26th, while the month's average Antarctic sea ice extent was 7.49 million square miles. September sea ice has grown by about 1 percent per decade in Antarctica. Albeit counterintuitive, the Antarctic is undergoing a warming, as much as 3°C (5°F) annually and by 5°C (9°F) in winter over the past 60 years along the Antarctic Peninsula. A recent study published in Polar Biology concluded that declines in two penguin species (the Adelie and Chinstrap) in western Antarctica were linked to the warming effect. The penguins failed to attain the better nesting spaces and lost access to food sources. Yet, a third penguin species (Gentoo) has adapted and its number increased. Another study addressed the future climate impacts from the potential release of methane gas as Antarctic glaciers melt. During September, researchers on a voyage to East Antarctica produced a three-dimensional (3-D) map of the underside of sea ice for the first time by using an Autonomous Underwater Vehicle (AUV). The AUV technology outfitted with multi-beam sonar was deemed a significant advance for measuring the thickness and volume of sea ice. Mapping obtained by the free-swimming robotic submarine will be combined with aerial measurements of surface snow and ice features to create a comprehensive 3-D map.

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Ecosystems Impacts

Desert locust swarms were present in northern Africa during September following a second generation breeding, where heavy rains resulted in favorable ecological conditions. Treatment for locusts was applied to over 1,500 acres in Chad, and about 100 acres in Sudan as part of sustainable disaster risk reduction efforts. Locusts also bred along the Indo-Pakistan border while vegetation was green. The U.S. Agency for International Development (USAID) provides disaster assistance in countries like Africa that are subject to emergency transboundary outbreak pests (ETOPs), which include locusts, grasshoppers, armyworm, and rodents. Active monitoring of ETOPs is conducted to minimize the threat they pose on food security and economic well-being of affected communities.

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Synoptic Discussion

Note: This Synoptic Discussion describes recent weather events and climate anomalies in relation to the phenomena that cause the weather. These phenomena include the jet stream, fronts and low pressure systems that bring precipitation, high pressure systems that bring dry weather, and the mechanisms which control these features — such as El Niño, La Niña, and other oceanic and atmospheric drivers (PNA, NAO, AO, and others). The report may contain more technical language than other components of the State of the Climate series.


NCDC transitioned to the nClimDiv dataset on Thursday, March 13, 2014. This was coincident with the release of the February 2014 monthly monitoring report. For details on this transition, please visit our public FTP site and our U.S. Climate Divisional Database site.


Synoptic Discussion

Monthly upper-level circulation pattern and anomalies
Monthly upper-level circulation pattern and anomalies.

The weather patternweather pattern over North America during September 2012 consisted of the seasonal battle between subtropical high pressure (High, or upper-level ridge) to the south and the polar jet stream and associated storm track to the north. The month began with the remnants of Hurricane Isaac entrained into a cold front draped across the Midwest to Northeast. After this system tracked out of the country, the jet stream frequently pushed upper-level troughs and cool fronts into the High over the eastern United States. When averaged over the month of September, this pattern resulted in warmer-than-average temperatures beneath a stronger-than-average upper-level ridge over the western U.S. and cooler-than-average temperatures beneath a stronger-than-average upper-level trough over the East. Showers and thunderstorms along the fronts and frontal lows dropped above-normal rainfall from the Southern Plains to the Midwest and parts of the Northeast, while summer monsoon showers brought above-normal precipitation to parts of the Southwest and frequent storms gave Alaska the fifth wettest September in the state's 1918-2012 record. But descending air ("subsidence") associated with the High dominated the West and Northern Plains, giving Montana, Minnesota, and the Dakotas the driest September in the 1895-2012 record. Numerous wildfires broke out in the hot, dry, windy weather across the West, especially in the Northwest, giving September 2012 near-record high acreage burned and near-record average size of fire. This weather pattern inhibited the formation of tornadoes, with the preliminary national count of 43 tornadoes being below the long-term average.

The movement of fronts across the South and East, and monsoon showers in the Southwest, can be seen in the weekly above-normal precipitation anomaly patterns (weeks 1, 2, 3, 4). The persistent dryness in the Northwest, Northern Plains, and Upper Midwest is also evident. The weather pattern during September shielded the U.S. mainland from most tropical activity. All of the four hurricanes and tropical storms active in the North Atlantic during September were steered away from the U.S. mainland. The remnants of Hurricane Isaac at the beginning of the month, and rains from subsequent frontal passages, helped shrink drought in the Ohio Valley where Kentucky and Ohio had the tenth wettest, or wetter, September in the 1895-2012 record. Ten states, from Wisconsin to the Pacific Northwest coast, had the tenth driest, or drier, September, with drought expanding in the Northern Plains and Upper Midwest. According to the end-of-September (October 2) U.S. Drought Monitor, 64.6% of the contiguous U.S. (54.0% of the U.S. including Alaska, Hawaii, and Puerto Rico) was affected by moderate to exceptional drought overall. These values are slightly higher than those at the end of August. According to the Palmer Drought Index, which goes back to the beginning of the 20th century, 51.9% of the contiguous U.S. was in moderate to extreme drought, a decrease of about 3 percent compared to last month. The 2012 Palmer Drought Index percent area values have been exceeded only by the droughts of the 1930s and 1950s.

The movement of the cool fronts can also be seen in the weekly temperature anomaly maps (weeks 1, 2, 3, 4). The persistence of warm anomalies in the West, and frequent excursions of cool air masses into the central and eastern U.S., gave four states in the West the tenth warmest, or warmer, September in the 1895-2012 record, while seven states in the Midwest and South had cooler-than-normal monthly temperatures. On a local basis, more than twice as many record warm highs and lows occurred than record cold highs and lows. Nearly 1050 daily high temperature records and 2150 record warm daily low temperatures were tied or broken. In comparison, about 750 record low temperatures and 630 record cool daily high temperatures were tied or broken. (These numbers are preliminary and are expected to increase as more data arrive.)

When averaged together, the mixture of temperature and precipitation extremes gave the U.S. the 23rd warmest and 48th driest September in the 118-year record. Averaging extremes tends to cancel them out (as in the case for national precipitation this month). But when extremes are combined cumulatively, like in the U.S. Climate Extremes Index (CEI), they may tell a different story. Nationally, the large spatial extent of very dry conditions ranked fourth largest for September 2012 (behind September 1934, 1954, and 1956). However, the CEI components for percent area with very warm maximum temperatures and days with no rain ranked only in the top 20, and the other components ranked even lower, giving the U.S. a September CEI that ranked only 39th largest. Regionally, the September 2012 CEI for the West North Central and West regions ranked sixth and seventh largest, respectively. The preponderance of unusual warmth and dryness for the last several months has ranked the national CEI largest for the warm season (April-September) and year-to-date (January-September), and second largest for the last twelve months (October-September).

Subtropical highs, and cold fronts and low pressure systems moving in the storm track flow, are influenced by the broadscale atmospheric circulation. Five such large-scale atmospheric circulation drivers were potentially influential during September:

Map of monthly temperature anomalies Map of monthly precipitation anomalies

Upper-level circulation pattern and anomalies averaged for the last three months
Upper-level circulation pattern and anomalies averaged for the last three months.

Examination of these circulation indices and their teleconnection patterns, and comparison to observed September and July-September 2012 temperature, precipitation, and circulation patterns, suggests that ENSO, PNA, and NAO had little influence on the observed weather patterns. The AO and EP-NP may have exerted some influence on the weather this past month and season. The temperature patterns over the last three months, especially the frequent movement of cold fronts across the U.S. east of the Rockies, and upper-level circulation patterns reasonably reflect the transition from a negative to a positive EP-NP. As noted above, some of the indices were near neutral values for part or much of the month. When the atmospheric circulation drivers are neutral or in a state of transition, their influence becomes difficult to trace and can be overwhelmed by other competing forces, including random fluctuations in the atmosphere.

Tornadoes

NCDC transitioned to the nClimDiv dataset on Thursday, March 13, 2014. This was coincident with the release of the February 2014 monthly monitoring report. For details on this transition, please visit our public FTP site and our U.S. Climate Divisional Database site.


September 2012 Tornadoes Year-to-date
January-September Tornado Counts

According to data from NOAA's Storm Prediction Center, during September, there were 43 preliminary tornado reports. This is less than the 1991-2010 September average of 74 tornadoes, and marks the least active September in terms of tornado activity since 2009, when eight tornadoes were confirmed. The majority of the tornadoes were weak and associated with the remnants of Hurricane Isaac as it moved through the Lower Mississippi River Valley and into the Midwest early in the month. There were also no tornado-related fatalities during September. The below-average tornado activity was similar to the rest of 2012 to-date. The preliminary number of tornadoes during the January-September period was 843 with 119 tornado reports still pending for July, August, and September, marking the lowest January-September tornado count since 2002.

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Hurricanes & Tropical Storms

NCDC transitioned to the nClimDiv dataset on Thursday, March 13, 2014. This was coincident with the release of the February 2014 monthly monitoring report. For details on this transition, please visit our public FTP site and our U.S. Climate Divisional Database site.


Note: This report catalogs recent tropical cyclones and places each basin's tropical cyclone activity in a climate-scale context. It is not updated in real time. Users seeking real time status and forecasts of tropical cyclones should visit The National Hurricane Center.

Atlantic Basin

Michael
Tropical Storm Michael Satellite Image


Michael Track
Tropical Storm Michael Track


Safir Simpson Color Legend for Track Map from Unisys
Saffir-Simpson Scale Color Legend
Tropical Cyclone Summary
Tropical Cyclone Michael
Cyclogenesis Date 09/04
Cyclolysis Date 09/11
Highest Saffir-Simpson Category Cat 3
Maximum 6-hr Sustained Wind 115 mph (100 kt or 185 km/h)
Min Pressure 964 mbar
Accumulated Cyclone Energy (ACE*) Index (kt2) 16.7725 x 104
Landfall Information (date, location and sustained winds)
Deaths 0
*The (ACE) Index calculations are based on preliminary data.

Nadine
Tropical Storm Nadine Satellite Image


Nadine Track
Tropical Storm Nadine Track


Safir Simpson Color Legend for Track Map from Unisys
Saffir-Simpson Scale Color Legend
Tropical Cyclone Summary
Tropical Cyclone Nadine
Cyclogenesis Date 09/12
Cyclolysis Date 10/04
Highest Saffir-Simpson Category Cat 1
Maximum 6-hr Sustained Wind 92 mph (80 kt or 148 km/h)
Min Pressure 978 mbar
Accumulated Cyclone Energy (ACE*) Index (kt2) 27.2050 x 104>
Landfall Information (date, location and sustained winds)
Deaths 0
*The (ACE) Index calculations are based on preliminary data.

West North Pacific Basin

Sanba
Tropical Storm Sanba Satellite Image
Sanba Track
Tropical Storm Sanba Forecast Track


Safir Simpson Color Legend for Track Map from Unisys
Saffir-Simpson Scale Color Legend
Tropical Cyclone Summary
Tropical Cyclone Sanba(Karen)
Cyclogenesis Date 09/11
Cyclolysis Date 09/17
Highest Saffir-Simpson Category Cat 5
Maximum 6-hr Sustained Wind 173 mph (150 kt or 278 km/h)
Min Pressure 900 mbar
Accumulated Cyclone Energy (ACE*) Index (kt2) 25.4250 x 104
Landfall Information (date, location and sustained winds) 09/17 - southern coast of South Korea (80 kt or 148 km/h)
Deaths 2
*The (ACE) Index calculations are based on preliminary data.

Jelawat
Tropical Storm Jelawat Satellite Image
Jelawat Track
Tropical Storm Jelawat Forecast Track


Safir Simpson Color Legend for Track Map from Unisys
Saffir-Simpson Scale Color Legend
Tropical Cyclone Summary
Tropical Cyclone Jelawat(Lawin)
Cyclogenesis Date 09/20
Cyclolysis Date 10/01
Highest Saffir-Simpson Category Cat 5
Maximum 6-hr Sustained Wind 161 mph (140 kt or 259 km/h)
Min Pressure 905 mbar
Accumulated Cyclone Energy (ACE*) Index (kt2) 45.2400 x 104
Landfall Information (date, location and sustained winds)
Deaths 7
*The (ACE) Index calculations are based on preliminary data.

Ewiniar
Tropical Storm Ewiniar Satellite Image
Ewiniar Track
Tropical Storm Ewiniar Forecast Track


Safir Simpson Color Legend for Track Map from Unisys
Saffir-Simpson Scale Color Legend
Tropical Cyclone Summary
Tropical Cyclone Ewiniar
Cyclogenesis Date 09/24
Cyclolysis Date 09/30
Highest Saffir-Simpson Category TS
Maximum 6-hr Sustained Wind 63 mph (55 kt or 102 km/h)
Min Pressure 985 mbar
Accumulated Cyclone Energy (ACE*) Index (kt2) 4.8000 x 104
Landfall Information (date, location and sustained winds)
Deaths
*The (ACE) Index calculations are based on preliminary data.

East North Pacific Basin

Kristy
Tropical Storm Kristy Satellite Image
Kristy Track
Tropical Storm Kristy Forecast Track


Safir Simpson Color Legend for Track Map from Unisys
Saffir-Simpson Scale Color Legend
Tropical Cyclone Summary
Tropical Cyclone Kristy
Cyclogenesis Date 09/12
Cyclolysis Date 09/17
Highest Saffir-Simpson Category TS
Maximum 6-hr Sustained Wind 58 mph (50 kt or 93 km/h)
Min Pressure 998 mbar
Accumulated Cyclone Energy (ACE*) Index (kt2) 2.8075 x 104
Landfall Information (date, location and sustained winds)
Deaths
*The (ACE) Index calculations are based on preliminary data.

Lane
Tropical Storm Lane Satellite Image
Lane Track
Tropical Storm Lane Forecast Track


Safir Simpson Color Legend for Track Map from Unisys
Saffir-Simpson Scale Color Legend
Tropical Cyclone Summary
Tropical Cyclone Lane
Cyclogenesis Date 09/15
Cyclolysis Date 09/19
Highest Saffir-Simpson Category Cat 1
Maximum 6-hr Sustained Wind 81 mph (70 kt or 130 km/h)
Min Pressure 989 mbar
Accumulated Cyclone Energy (ACE*) Index (kt2) 4.2875 x 104
Landfall Information (date, location and sustained winds)
Deaths
*The (ACE) Index calculations are based on preliminary data.

Bolaven
Tropical Storm Bolaven Satellite Image
Bolaven Track
Tropical Storm Bolaven Forecast Track


Safir Simpson Color Legend for Track Map from Unisys
Saffir-Simpson Scale Color Legend
Tropical Cyclone Summary
Tropical Cyclone Bolaven(Julian)
Cyclogenesis Date 09/19
Cyclolysis Date 09/28
Highest Saffir-Simpson Category Cat 4
Maximum 6-hr Sustained Wind 145 mph (125 kt or 200 km/h)
Min Pressure 910 mbar
Accumulated Cyclone Energy (ACE*) Index (kt2) 28.5000 x 104
Landfall Information (date, location and sustained winds)
Deaths 88
*The (ACE) Index calculations are based on preliminary data.

Miriam
Tropical Storm Miriam Satellite Image
Miriam Track
Tropical Storm Miriam Forecast Track


Safir Simpson Color Legend for Track Map from Unisys
Saffir-Simpson Scale Color Legend
Tropical Cyclone Summary
Tropical Cyclone Miriam
Cyclogenesis Date 09/22
Cyclolysis Date 09/27
Highest Saffir-Simpson Category Cat 3
Maximum 6-hr Sustained Wind 121 mph (105 kt or 194 km/h)
Min Pressure 958 mbar
Accumulated Cyclone Energy (ACE*) Index (kt2) 9.6600 x 104
Landfall Information (date, location and sustained winds)
Deaths
*The (ACE) Index calculations are based on preliminary data.

Norman
Tropical Storm Norman Satellite Image
Norman Track
Tropical Storm Norman Forecast Track


Safir Simpson Color Legend for Track Map from Unisys
Saffir-Simpson Scale Color Legend
Tropical Cyclone Summary
Tropical Cyclone Norman
Cyclogenesis Date 09/28
Cyclolysis Date 09/28
Highest Saffir-Simpson Category TS
Maximum 6-hr Sustained Wind 46 mph (40 kt or 74 km/h)
Min Pressure 1000 mbar
Accumulated Cyclone Energy (ACE*) Index (kt2) .5650 x 104
Landfall Information (date, location and sustained winds)
Deaths 1
*The (ACE) Index calculations are based on preliminary data.

Drought

NCDC transitioned to the nClimDiv dataset on Thursday, March 13, 2014. This was coincident with the release of the February 2014 monthly monitoring report. For details on this transition, please visit our public FTP site and our U.S. Climate Divisional Database site.

Issued 15 October 2012
Contents Of This Report:
Map showing Palmer Z Index

National Drought Overview

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Detailed Drought Discussion

Overview

September 2012 was another month with warmer-than-average temperatures (23rd warmest September on record, based on data back to 1895) and near-average precipitation (48th driest September), when weather conditions are averaged across the country. Like last month, cool fronts swept across the central and eastern U.S. (weeks 1, 2, 3, 4) while a strong high pressure system (High, or upper-level ridge) kept its stranglehold over much of the West, resulting in a monthly pattern of anomalous warmth in the West and below-normal temperatures in the Midwest and Southeast. Descending air ("subsidence") associated with the High inhibited precipitation in the Northwest to Upper Midwest, while passing fronts and the remnants of Hurricane Isaac triggered areas of rain from the Southern Plains to the Midwest and parts of the Northeast; monsoon showers brought rain to the Southwest (weeks 1, 2, 3, 4); and frequent storms gave Alaska the fifth wettest September in the state's 1918-2012 record. The dry weather in the Northwest and Northern Plains, in combination with the above-normal rainfall in the Ohio Valley and Southern Plains, helped the drought areas migrate westward and northward. Nationally, the moderate-to-exceptional (D1-D4) drought footprint increased slightly to about 54 percent of the country, compared to last month, while the percentage in the abnormally dry to exceptional drought category decreased to about 68 percent. About 17 percent of the country was in the worst drought categories (D3-D4, extreme to exceptional drought), a bit less than last month. The Palmer Drought Index, whose data base goes back 113 years, is relied upon for drought comparisons before 2000. The September 2012 Palmer value of 52 percent in moderate to extreme drought is a decrease of about 3 percent compared to last month, and the percent area in severe to extreme drought decreased to about 37 percent.

The U.S. Drought Monitor drought map valid October 2, 2012
The U.S. Drought Monitor drought map valid October 2, 2012.

By the end of the month, the core drought areas in the U.S. included:


Palmer Drought Index

The Palmer drought indices measure the balance between moisture demand (evapotranspiration driven by temperature) and moisture supply (precipitation). The Palmer Z Index depicts moisture conditions for the current month, while the Palmer Hydrological Drought Index (PHDI) and Palmer Drought Severity Index (PDSI) depict the current month's cumulative moisture conditions integrated over the last several months.

Palmer Z Index map Palmer Hydrological Drought Index map

Rain from frontal systems and the remnants of Hurricane Isaac (as seen on the Palmer Z Index map) effectively ended drought in parts of the Midwest (PDSI from end of September compared to end of August). Dry conditions in the Upper Midwest and Northern Plains, and warmer- and drier-than-normal weather across the Northern Rockies and Pacific Northwest, intensified drought in the Plains (both short-term [Z Index] and long-term [PHDI] conditions) and expanded drought to the north and west. Recent dryness (August and September Palmer Z Index maps) neutralized previously long-term wet conditions in the Northwest, while wet September conditions reduced longer-term dry conditions in the Northeast. The Palmer maps also reflect the long-term nature of the drought conditions. The Z Index and PHDI maps in combination show that precipitation brought relief to parts of the Southern Plains to Midwest and Northeast drought areas, and reduced precipitation continued to shrink long-term wet areas in the Northwest, but for the Upper Midwest to Central and Northern Rockies — drier-than-normal weather persisted over the existing drought areas.


Standardized Precipitation Index

The Standardized Precipitation Index (SPI) measures moisture supply. The SPI maps here show the spatial extent of anomalously wet and dry areas at time scales ranging from 1 month to 24 months.

1-month Standardized Precipitation Index 2-month Standardized Precipitation Index 3-month Standardized Precipitation Index

The 1-month SPI shows the main area of dryness from the Pacific Northwest to the Northern and Central Plains and Upper Midwest, with other areas dry in parts of the Southeast and much of California. The western and central regions' dryness persists at 2 and 3 months, with dryness spreading across more of the Central Plains and into the Southern Plains and Southern Rockies at 3 months. At 6 months, the April-September growing season was quite dry across the Midwest and Great Plains agricultural belt and into the Rocky Mountain states as well as parts of the Southeast and coastal Mid-Atlantic. The 6-month pattern is generally evident at 9 and 12 months with expansion of dryness further into the West. Dryness at 24 months is concentrated in the Southern to Central Plains, Southern to Central Rockies, and Southeast. Wet conditions from the Southwest monsoon appear in places from 1 to 6 months, and wetness from frontal and tropical moisture stretches from the Southern Plains to Northeast at 1 to 3 months. The Pacific Northwest and central Gulf of Mexico coast are wet at 9 months, while widespread wetness dominates at 24 months from the Ohio Valley to Northeast.


6-month Standardized Precipitation Index 12-month Standardized Precipitation Index 24-month Standardized Precipitation Index


Agricultural and Hydrological Indices and Impacts

USDA topsoil moisture short to very short
USDA topsoil moisture short to very short
USGS monthly streamflow percentiles
USGS monthly streamflow percentiles

Drought conditions were reflected in numerous agricultural, hydrological, and other meteorological indicators, both observed and modeled.

Agricultural:

At some point during 2012, most of the counties in the country had been declared agricultural disaster areas by the U.S. Department of Agriculture (USDA). Based on end-of-September (September 30th) USDA reports, 55 percent of the nation's pasture and rangeland was rated in poor to very poor condition. Several states, from California to the Central Plains, had 80 percent or more of their pasture and rangeland rated poor to very poor, with virtually all of it so rated in Nebraska. Much of the nation's corn and soybean crops have been harvested, but winter wheat was 40 percent planted and its emergence was hampered by drought in several central and northwestern states, with 71 percent of the winter wheat in drought. While topsoil moisture has recovered in Midwest states receiving rainfall during the last couple months, more than 80 percent of the topsoil was rated short or very short of moisture from the Upper Midwest to Northern and Central Plains, and in the Rocky Mountain states.

Map showing USDA pasture and rangeland conditions
Map showing USDA pasture and rangeland conditions.

Hydrological:

USGS groundwater percentile map
USGS groundwater percentile map.

Meteorological:

Map showing number of days with precipitation
Map showing number of days with precipitation.


Regional Discussion

Hawaii: September 2012 was characterized by below-normal rainfall over the Big Island stations but a mixed pattern over most of the rest of the Hawaiian Islands. A similar pattern exists for the last 2 to 3 months. Longer-term conditions continued drier than normal (last 6, 12, 24, and 36 months, and year-to-date), especially for the southern islands. Moderate to extreme drought affected 51 percent of the state, a little less than last month.

Alaska: September 2012 was drier than normal in the southeast interior region and wetter than normal across most of the rest of the state. A similar pattern could be seen at 2, 3, and 6 months, but the pattern becomes mixed at longer time scales (last 9, 12, 24, and 36 months). An area of abnormal dryness covered the northern areas on the USDM map.

Puerto Rico: It was drier than normal across much of the island during September, but especially in the south and east. Streamflow averaged below normal for the month at several locations. A dry band stretched from the west coast to the central regions, culminating in a drier-than-normal eastern third of the island, at 2 to 3 months, and even at 6 months. But the drier-than-normal area transitioned to the southeast at longer time scales (6 months, year to date, and water year to date). The October 2nd USDM map had an area of abnormally dryness in the south central to eastern areas to reflect these rainfall deficits.

Current month state precipitation ranks 3-month state precipitation ranks

Nebraska statewide precipitation, May-September, 1895-2012
Nebraska statewide precipitation, May-September, 1895-2012.

A fourth of the U.S. was very dry (the driest ten percent of the historical record) during September 2012. The dryness was partially balanced out by a significant area (about 8 percent) that was very wet, resulting in a national rank for September 2012 of 48th driest September in the 118-year record. On a statewide basis, September 2012 ranked in the top ten driest Septembers for ten states — from the Northwest to the Upper Midwest — and ranked as the driest September for Montana, North Dakota, South Dakota, and Minnesota. Six other states ranked in the driest third of the historical record. The same spatial pattern of dryness existed at the three month time scale. Again, Montana and South Dakota, along with Nebraska, had the driest July-September on record. Eight other states had the tenth driest, or drier July-September and four other states ranked in the driest third of the historical record.

6-month state precipitation ranks 12-month state precipitation ranks

Wyoming statewide precipitation, January-September, 1895-2012
Wyoming statewide precipitation, January-September, 1895-2012.

The spatial pattern of dryness at the six month time scale is centered in the Central Rockies to Central Plains. The persistent dryness gave Nebraska and Wyoming the driest April-September on record, with six other states ranking in the top ten driest category. Twelve additional states were in the driest third of the historical record. A similar pattern was evident for the year-to-date. At the 12-month time scale, dryness dominated from the West to the Midwest, with pockets of dryness in the Southeast and coastal Mid-Atlantic. October 2011-September 2012 ranked in the top ten driest category for eight states, with 14 other states ranking in the driest third of the historical record. Nebraska ranked second driest, with Delaware and Wyoming ranking third driest, for October 2011-September 2012. It should be noted that the dryness this year has been so extreme and persistent that, not only did several states rank driest for several time scales (as noted above), but their records were by wide margins compared to the previous records. The last two years have been so dry that New Mexico has had the driest 24-month October-September period in the 1895-2012 record. The last two years (October 2010-September 2012) have also tied with October 1998-September 2000 as the warmest such 24-month period for New Mexico.

Moisture Stress Index for corn, 1900-2012 Moisture Stress Index for soybeans, 1900-2012


Corn and Soybean Belt

Drought Maps for Selected Months
Year July
Palmer Z Index
August
Palmer Z Index
September
PDSI
1936 X X X
1930 X X X
1901 X X X
2012 X X X

The Primary Corn and Soybean agricultural belt has been especially hard hit by drought this year. The crop Moisture Stress Index (MSI) measures the impact of extreme dryness, as well as excessively moist conditions, on productivity of corn and soybeans by using the Palmer Z Index as an indicator. The MSI is computed annually. It shows the impact of current weather conditions on the productivity of the modern corn and soybean agricultural area compared to how past weather conditions would have theoretically impacted this modern agricultural area's productivity. The 2012 MSI for corn ranked as the fourth worst MSI in the 1900-2012 record, behind 1936, 1930, and 1901. The 2012 MSI for soybeans also ranked as the fourth worst MSI in the 1900-2012 record, behind 1936, 1930, and 1901 as well. The MSI analysis is based on the July-August Palmer Z Index, which reflects moisture conditions during an important part of the growing season. The July and August Palmer Z Index maps, as well as the September Palmer Drought Severity Index map, for these four years can be accessed via the table to the right. In each case, severely dry (short-term drought) conditions afflicted much of the agricultural belt during July and August. The short-term (Palmer Z Index) drought conditions were more important to the productivity of these crops than the longer-term (PDSI) drought conditions.


Western U.S.


Percent area of the Western U.S. in moderate to extreme drought, based on the Palmer Drought Index
Percent area of the Western U.S. in moderate to extreme drought, based on the Palmer Drought Index.

Like the last two months, showers and thunderstorms from the waning summer monsoon brought above-normal rainfall to parts of the Southwest this month, but most of the West was dry, especially from the Pacific Northwest to Northern Rockies where Montana had the driest September on record, Washington ranked second driest, and Oregon third driest. The combination of dryness and well above-normal temperatures resulted in a large area of severe to extreme short-term drought. The rain that fell in the extreme Southwest did little to change the overall percent area in drought. Drier-than-normal weather has dominated much of the West for the water year (October 2011-September 2012), as reflected in low elevation as well as high elevation (SNOTEL) precipitation, especially for the southern half of the West. Reservoir storage was below average, statewide, in most of the western states. Hot, dry, windy weather contributed to many wildfires across the West. According to the USDM, 77 percent of the West was experiencing moderate to exceptional drought at the end of September, a 3 percent increase compared to August. The Palmer Drought Index percent area statistic was about 53 percent, a decrease of two percent compared to last month.

A more detailed drought discussion, provided by the NOAA Regional Climate Centers and others, can be found below.

SoutheastSouthMidwestNortheastHigh Plains
WestUpper Colorado River BasinPacific Islands

As noted by the Southeast Regional Climate Center, precipitation was highly variable across the region. The driest locations were found along coastal sections of Virginia and South Carolina, where monthly rainfall totals were less than 50 percent of normal. For the second straight month, mean temperatures were near normal across much of the Southeast region. Drought conditions remained fairly stable across the Southeast in September, with approximately one-third of the region classified in drought (D0 and greater) according to the USDM by the end of the month. Wet weather and saturated ground impeded the harvesting of hay, cotton, and peanuts across parts of Alabama, Georgia, and Florida. The planting of sugarcane and winter vegetables was also delayed across parts of Florida due to wet conditions over the past several months. The persistence of wet conditions also contributed to fungal diseases as well as outbreaks of mold and mildew in several different crops across parts of Florida and North Carolina. In contrast, the persistence of dry conditions across central Georgia continued to limit pasture growth.

As explained by the Southern Regional Climate Center, September precipitation in the Southern region varied spatially, with most regions receiving either anomalously high or anomalously low amounts of precipitation. September temperatures in the region were generally at or above normal. Heavy rainfall amounts in the Southern region led to some improvements to drought conditions. In Arkansas, the northeastern counties improved from extreme and exceptional drought to severe drought conditions. Conditions are also improved for much of western Tennessee. Moderate to severe drought conditions were also scaled back in northern Louisiana and southern Arkansas. Elsewhere, drought conditions did not significantly change. Much of Oklahoma and southern Texas remain in extreme drought or worse, while moderate drought conditions are still prevalent in central and western Texas. Texas rainfall has helped mitigate many of the short-term drought effects, as seen in central Texas, where cotton farmers are expecting a 75 percent higher yield than last year and ranchers were provided relief as livestock overhead has been increasing due to rising feed prices. Hydrological improvements of these rains are limited, however. While San Angelo is expecting 50,000+ acre-feet to be recovered to O. H. Ivie Reservoir, Jonestown's lake and reservoir levels are still so low that their revenues from water-sport related purchases are down and have been put in a budget crunch to the tune of $363,000. Ecological impacts are also still being felt, as Longview's forestry service has gone far above budget removing trees killed by lasting drought conditions. The service has already spent nearly $90,000 on tree removal, with an estimated 301 million dead trees still requiring removal (Information Provided by the Texas State Climate Office).

As summarized by the Midwest Regional Climate Center, September precipitation varied drastically from dry in the north to wet in the south. Minnesota recorded its driest September on record (118 years) with many stations recording less than a half inch (13 mm) of rain while precipitation totals in southern Illinois topped 14 inches (356 mm) at several stations. As a percentage of normal, the totals ranged from less than 10 percent to more than five times normal. Heavy September rains in Ohio (4th wettest) and Kentucky (7th wettest) were in contrast to the drier conditions to the north where Minnesota recorded its driest September and Wisconsin had its 9th driest. June to September was the driest on record in Iowa and May to September was the third driest in Missouri. Year-to-date precipitation totals rank among the top 12 driest years since 1895 in five states: Iowa (4th), Illinois (7th), Missouri (8th), Indiana (12th), and Wisconsin (12th). The Midwest regional temperature was slightly below normal in September, breaking a string of 11 straight months above normal from October 2011 to August 2012. For the first time since January 2011, none of the nine Midwest states had an above normal statewide temperature. Drought conditions eased in the southern half of the region but further north there was both expansion and intensification of drought. Overall, the Midwest saw an increase from 82 percent to 91 percent of the region in drought during September but severe drought dropped from 50 to 42 percent and extreme drought dropped from 33 to 15 percent. Missouri saw the biggest improvements going from 97 to just 17 percent areal coverage of extreme drought, though the entire state remained in drought. Minnesota saw the biggest expansion and intensification with drought areas increasing from 38 to 96 percent of the state and extreme drought increasing from 0 to 20 percent. Improvements in the southern parts of the Midwest came too late in the year to help the corn crop. Harvest was on pace or ahead of normal for major crops in the Midwest. Corn harvest was ahead of normal across the region. Soybean harvest was near normal in the southeast but well ahead of normal in the northwest.

As noted by the Northeast Regional Climate Center, overall, the Northeast averaged wetter-than-normal during September. The average monthly temperature of 61.2 degrees F (16.2 degrees C) was 0.4 degrees F (0.2 degrees C) above normal. This is the third month in a row to average warmer than normal. Above normal rainfall during September alleviated drought conditions in much of the Northeast. According to the USDM issued on October 2, 2012, southern Delaware was still experiencing moderate (D1) and severe (D2) drought. Conditions in southern Maryland improved to a mix of D0 and D1, with only a very small D2 area along the border with Delaware. Portions of upstate New York, mainly east of Lakes Erie and Ontario, were still experiencing moderate drought (D1) at month's end.

As explained by the High Plains Regional Climate Center, while most the High Plains region had near normal average temperatures, September 2012 continued to be dry for the majority of the region. Precipitation totals which were less than 50 percent of normal were widespread. In addition, a large area of central and northern South Dakota and pockets of North Dakota, Nebraska, and Wyoming received at most 5 percent of normal precipitation. This dearth of precipitation caused many new records to be set this month. Aberdeen, South Dakota had its driest September on record with only 0.01 inch (0 mm) of precipitation which was 2.18 inches (55 mm) below normal. The old record of 0.05 inch (1 mm) was set back in 1979 (period of record 1893-2012). Interestingly there were numerous stations across South Dakota that received no measurable precipitation this month. One of these locations was Pierre, South Dakota which tied with 1893 for its driest September on record (period of record 1893-2012). The dry weather continued to have an impact across the region. According to the U.S. Army Corps of Engineers, the Missouri River had record low inflows this month of just 0.3 million acre feet. The previous record occurred in 1919 with 0.4 million acre feet (period of record 1898-2012). In addition, water and feed shortages for livestock were common and many producers continued to cull livestock. The dry weather did help with crop dry down and by the end of the month, the corn harvest was well ahead of average in Nebraska and the Dakotas. The only areas of the region which received above normal precipitation were central and southeastern Colorado, and southwestern and eastern Kansas. These areas had precipitation totals ranging from 110 percent of normal to 300 percent of normal.

According to the USDM, there have been significant changes in drought conditions over the last month in the High Plains region. By the end of September, about 99 percent of the region was under moderate (D1) to exceptional (D4) drought, with nearly 24 percent of the region in the D4 designation. In contrast, at the end of last month, only 15 percent of the region was in D4. D4 areas expanded to include most of the state of Nebraska, a small portion of eastern Wyoming, southeastern South Dakota, northeastern Colorado and much of the western and central parts of Kansas. By the end of the month, just over 75 percent of Nebraska was in D4 drought. Extreme drought conditions (D3) also expanded in Nebraska, North Dakota, South Dakota, and Wyoming. In addition, every part of the region had at least some sort of drought designation or either abnormally dry conditions (D0). About the only improvements occurred in eastern Kansas, where the remnants of Hurricane Isaac helped downgrade drought conditions there.

As summarized by the Western Regional Climate Center, continuing this summer's theme of record heat and dry conditions, September 2012 saw above normal temperatures and below normal precipitation for much of the West. Late season monsoon activity over the southern Great Basin and Mojave Desert and a duo of storms hitting south-central Alaska brought locally heavy precipitation, while other locations remained parched. The North American monsoon season (June 15-Sept 30) wrapped up this month, with many locations receiving near or above their normal monsoon precipitation totals. Las Vegas, Nevada received 1.18 in (30 mm) on September 11th, the location's wettest September day on record. The downpours resulted in extensive flooding in the Las Vegas area. The month ranks as the 5th wettest in a record that began in 1937. In northern Arizona, Bagdad received 10 in (254 mm) for the monsoon season, 187 percent of normal for the station. Elsewhere in the region, Prescott and Flagstaff received 76 percent and 100 percent of their average Monsoon precipitation. Albuquerque, New Mexico finished the season at 72 percent of normal. September 2012 was the 5th wettest at Denver, Colorado, with a total of 2.95 in (74.9 mm) of rainfall. It was also the 12th consecutive September with no snowfall in Denver. The other 12-year stretch of no September snowfall occurred from 1914-1926. Precipitation was lacking elsewhere in the West, with many Pacific Northwest locations noting their driest Septembers on record and extended periods with no measurable precipitation. Both Billings and Missoula, Montana received only trace precipitation, their driest Septembers on records beginning in 1934 and 1893, respectively. At Missoula, it was only the second time in the station's history that any month in the year received no measurable precipitation. Sheridan, Wyoming also recorded only trace precipitation in September tying the driest on record. Beginning the 11th of August, 51 consecutive days passed at Sheridan without measurable precipitation, the longest dry period in a record beginning in 1920. In Washington, Spokane, Bellingham, and Olympia all set or tied their driest year-to-date on record. Dry conditions also dominated Hawaii, where Lihue, Kauai, received only 35 percent of its normal September rainfall. Precipitation at Lihue has been below average nine of eleven months of the current water year.

With dry fuels, high temperatures, and low relative humidity prevailing throughout the month, many large wildfires ignited or grew throughout September. Smoke from the fires lead to poor air quality in eastern Washington and Oregon, northern Idaho, western Montana, and Northern California. One of the largest, at 339,110 acres (137,233 hectares) by month's end, was the Mustang Fire on the Idaho-Montana border. The North Pass Fire, 10 miles northeast of Covelo, California, has burned 41,983 acres (16,990 hectares) and consumed 26 structures. The national average of large fire events for 2012 remains at 77 percent of the 10-year average, while acreage burned this year is at 129 percent of the recent average.

Upper Colorado River Basin: As reported by the Colorado Climate Center, the October 2nd NIDIS (National Integrated Drought Information System) assessment for the Upper Colorado River Basin (UCRB) indicated that, for Water Year 2012, most of the UCRB was drier than average. Some parts in central Utah and southwest Wyoming saw above average precipitation for the water year. The San Juan mountains in CO received near average precipitation. Northwest CO was the driest part of the basin, with most areas receiving between 30% and 70% of average water year precipitation. East of the basin, most of eastern CO saw between 70% and 90% of average water year precipitation, with parts of the Front Range, Saguache County, and the Sangre de Cristos receiving near average precipitation for the water year. As of September 30th, about 48% of the USGS streamgages in the UCRB recorded normal (25th - 75th percentile) or above normal 7-day average streamflows. About 35% percent of the gages in the basin are recording much below normal or low (i.e. lowest on record) streamflows (a decrease from 48% one week ago). Only 3% of the gages are recording above normal flows. As flows return to a normal baseflow, the rivers are expected to run lower, and small changes could mean larger changes in percentiles rankings. Accumulated volumes for this time of year is a better indicator of how runoff has been affected by dry conditions. Most of the UCRB and the rest of CO experienced warmer than average temperatures for the month of September. Satellite vegetation conditions show very dry vegetation through much of the northern part of the UCRB and throughout eastern CO. Improved vegetation conditions show up in the central and southern mountains of CO and also in southern UT. For the growing season, reference evapotranspiration (ET) rates were higher than average across the western slope (meaning more available water was being lost to the atmosphere than normal, largely due to the anomalously warm spring and summer). East of the basin, stations in southeast and northeast CO reported near record or record high reference ET accumulations for the growing season. For the month of September, all the major reservoirs in the UCRB saw a volume decrease, which is normal during this time of year. Navajo and Granby reservoirs decreased more than what is normal for this time of year, while Green Mountain decreased less than average. At the end of the month, many of the reservoirs were between 70% and 85% of average. Blue Mesa and Green Mountain are the lowest, at 53% and 60% of average respectively, and Flaming Gorge is the highest, at 97% of average.

Pacific Islands: According to reports from National Weather Service offices, the Pacific ENSO Applications Climate Center (PEAC), and partners, conditions varied across the Pacific Islands.

As noted by the National Weather Service office in Honolulu, the 2012 Hawaiian Islands dry season has concluded and, as expected, large areas of the state, especially in the leeward areas of Maui County and the Big Island, head into the new wet season under significant drought. Areas of extreme drought, or the D3 category in the USDM map, remain firmly in place. In Maui County, this includes the southwest slopes of Lanai, western Molokai and southwest Maui from Kihei to Makena. On the Big Island, extreme drought continues to cover most of the south Kohala district, the Pohakuloa region of the Hamakua district and the north-facing slopes of Hualalai in the north Kona district. Extreme drought has also redeveloped over the lower elevations of southwest Kau. On Kauai, severe drought, or D2 category conditions, covers the lower elevations from Kealia to Koloa, then westward to Waimea. Maui county D2 conditions include the lower leeward slopes of the west Maui Mountains and the leeward slopes of Haleakala from Kula to Kaupo. On the Big Island, the main area of severe drought persists in the Humuula Saddle. An increase in rainfall over the northeast half of Oahu has reduced the area of moderate drought, or D1 conditions, which is now mainly confined to the leeward sections of the Waianae range.

Some drought impacts impacts in Hawaii include the following:

KAUAI:
NO SIGNIFICANT CHANGES SINCE THE SEPTEMBER 6 UPDATE.  RECENT REPORTS
INDICATED POOR PASTURE CONDITIONS IN THE AREA FROM KALAHEO TO
HANAPEPE.  OTHER AREAS WITH POOR PASTURE CONDITIONS INCLUDE THE
REGION FROM KOLOA TO MAHAULEPU...AND FROM KEALIA TO KALEPA.

OAHU:
PASTURES AND GENERAL VEGETATION REMAIN IN POOR CONDITION OVER THE
LEEWARD WAIANAE RANGE.  REPORTS FROM EARLIER IN THE SUMMER INDICATED
THAT SOME RANCHERS DESTOCKED PASTURES IN THE WAIALUA...MAKAKILO AND
PALEHUA AREAS OF THE ISLAND.

THE WATER SUPPLY IN THE WAIMANALO RESERVOIR REMAINS ABOVE
PRE-DROUGHT LEVELS.  A VOLUNTARY 10 PERCENT REDUCTION IN WATER USE
REMAINS IN PLACE AS A PRECAUTION FOR THE DRY SEASON.

MOLOKAI:
NO SIGNIFICANT CHANGES SINCE THE SEPTEMBER 6 UPDATE.   PASTURES AND
GENERAL VEGETATION CONDITIONS REMAIN VERY POOR WEST OF KAUNAKAKAI.
AN EARLIER REPORT INDICATED THAT THE DRY CONDITIONS HAVE RESULTED IN
AN INCREASE IN AXIS DEER ENCROACHMENTS AND CROP DAMAGE AS THEY SEEK
FOOD AND WATER.

THE WATER LEVEL IN THE KUALAPUU RESERVOIR REMAINS VERY LOW.
THUS...THE STATE OF HAWAII DEPARTMENT OF AGRICULTURE HAS CONTINUED A
MANDATORY 30 PERCENT REDUCTION IN IRRIGATION WATER CONSUMPTION.

LANAI:
A RECENT REPORT FROM LANAI INDICATED THAT THE MIDDLE AND LOWER
ELEVATIONS OF THE ISLAND...ESPECIALLY ALONG THE NORTH-...EAST- AND
SOUTH-FACING SLOPES...REMAIN VERY DRY AND THAT PLANTS AND ANIMALS IN
THESE AREAS HAVE BEEN STRUGGLING TO SURVIVE.  EVEN DROUGHT-RESISTANT
PLANTS AND TREES SUCH AS KIAWE WERE STRUGGLING UNDER THE DRY
CONDITIONS.  MOUFLON SHEEP...AXIS DEER AND GAME BIRD POPULATIONS
HAVE BEEN REDUCED.

MAUI:
SPOTTY LEEWARD RAINFALL IN SEPTEMBER MAY HAVE HELPED PREVENT A
WORSENING OF DROUGHT BUT IT IS TOO SOON TO TELL HOW MUCH OF AN
IMPROVEMENT IT MAY HAVE PRODUCED...IF AT ALL.  THE CURRENT SHORT
TERM DRY TREND OVER THE PAST 2 WEEKS MAY BE NEGATING ANY IMPACTS
THE MID-SEPTEMBER RAINS HAVE GENERATED.  AN EARLIER REPORT
INDICATED THAT UPCOUNTRY AGRICULTURE CONTINUES TO BE SIGNIFICANTLY
IMPACTED BY  THE ONGOING DROUGHT.  MEDIA REPORTS INDICATED THAT
RANCHERS HAVE HAD TO INCREASE IRRIGATION...SUPPLEMENT FEED AND
REDUCE HERD SIZES. ENCROACHING AXIS DEER HAVE ALSO DECREASED FORAGE
FOR LIVESTOCK. BRUSH FIRE RISK...ESPECIALLY ALONG THE SOUTHWEST
SLOPES OF HALEAKALA...IS EXTREMELY HIGH.  THE MAUI COUNTY DEPARTMENT
OF WATER SUPPLY HAS CONTINUED THE ONGOING CALL FOR A 5 PERCENT
REDUCTION IN WATER USE FOR UPCOUNTRY RESIDENTS.  THE REQUEST FOR A
10 PERCENT REDUCTION IN WATER USE BY CENTRAL AND SOUTH MAUI ALSO
REMAINS IN EFFECT.

BIG ISLAND:
THE WORSENING OF DROUGHT IN THE SOUTH POINT AREA HAS FORCED SOME
RANCHERS TO REDUCE HERD SIZES BY 25 PERCENT AND PURCHASE
SUPPLEMENTAL FEED.  NEARBY FLOWER GROWERS HAVE HAD TO SPEND
EXCESSIVE AMOUNTS OF MONEY TO FILL CATCHMENT TANKS FOR IRRIGATION.
IN THE KAU...NORTH KONA...SOUTH KONA AND SOUTH KOHALA
DISTRICTS...THE DROUGHT HAS REDUCED THE AMOUNT OF NECTAR AVAILABLE
FOR BEES AND IS NEGATIVELY AFFECTING THE BEE INDUSTRY. LEEWARD
KOHALA COASTAL PASTURES HAVE BEEN WITHOUT ADEQUATE FORAGE FOR MANY
MONTHS AND RANCHERS HAVE BEEN CONTINUING WITH COSTLY WATER HAULING
AND SUPPLEMENTAL FEED OPERATIONS.

SPI values for seven time periods for Hawaiian Island stations, computed by the Honolulu NWS office.
SPI values for seven time periods for Hawaiian Island stations

On other Pacific Islands (maps — Micronesia, Marshall Islands, basinwide), September was drier than normal for Kwajalein and Majuro, and slightly below normal for Chuuk and Pohnpei, but near to above normal for the rest of the stations. Total rainfall for the last 12 months (October 2011-September 2012) was near to above normal for all stations, except Majuro was trending below normal.


X
  • Percent of Normal Precip
  • Precipitation
  • Normals
Pacific Island Percent of 1981-2010 Normal Median Precipitation
Station NameOct
2011
Nov
2011
Dec
2011
Jan
2012
Feb
2012
Mar
2012
Apr
2012
May
2012
Jun
2012
Jul
2012
Aug
2012
Sep
2012
Oct 2011-
Sep 2012
Chuuk97%136%125%57%181%107%40%173%131%141%169%86%114%
Guam NAS135%83%103%162%94%215%121%224%107%66%179%126%108%
Kapingamarangi57%81%124%109%71%121%102%143%179%146%192%147%111%
Koror12%62%97%36%126%121%120%122%95%88%102%111%82%
Kosrae154%95%174%65%185%60%84%86%99%124%144%109%94%
Kwajalein125%130%84%134%114%84%68%161%117%120%95%57%103%
Lukonor56%154%251%86%124%135%76%106%125%82%73%148%101%
Majuro115%119%91%107%65%194%97%59%81%68%87%67%92%
Pago Pago137%157%75%61%98%131%90%126%115%105%59%195%96%
Pohnpei77%123%110%82%138%98%45%115%100%92%96%90%93%
Saipan140%57%110%77%183%35%33%166%118%77%135%101%105%
Yap101%112%116%33%117%185%89%142%99%84%128%187%111%
Pacific Island Precipitation (Inches)
Station NameOct
2011
Nov
2011
Dec
2011
Jan
2012
Feb
2012
Mar
2012
Apr
2012
May
2012
Jun
2012
Jul
2012
Aug
2012
Sep
2012
Oct 2011-
Sep 2012
Chuuk11.1414.4414.015.7413.138.875.0219.5615.2716.9221.7810.04155.92
Guam NAS15.456.145.246.502.854.453.057.636.636.7426.4215.98107.08
Kapingamarangi4.637.5412.199.946.6113.8213.9117.2424.6820.6515.5714.56161.34
Koror1.397.0410.793.6510.819.038.7914.4916.5416.3613.7213.01125.62
Kosrae16.8313.0728.1110.8923.939.5914.7015.3514.5618.5520.4615.52201.56
Kwajalein14.0014.685.594.223.011.973.5810.828.0811.839.236.1793.18
Lukonor6.3814.0228.347.2211.0612.518.6012.3514.5313.0810.2615.02153.37
Majuro14.6515.9710.378.274.4612.759.145.968.897.5410.157.47115.62
Pago Pago12.6715.919.698.1411.7614.008.4112.156.135.843.1912.73120.62
Pohnpei11.7418.2117.6110.7513.1712.928.3122.9814.8614.2113.6211.27169.65
Saipan14.903.224.231.964.750.660.883.964.266.8617.7310.2473.65
Yap12.329.929.912.116.098.435.0011.1411.9512.7418.9225.19133.72
Pacific Island 1981-2010 Normal Median Precipitation (Inches)
Station NameOct
2011
Nov
2011
Dec
2011
Jan
2012
Feb
2012
Mar
2012
Apr
2012
May
2012
Jun
2012
Jul
2012
Aug
2012
Sep
2012
Oct 2011-
Sep 2012
Chuuk11.5110.6111.2510.107.258.3212.4711.3011.6611.9812.8611.71136.77
Guam NAS11.447.385.114.013.032.072.533.406.1810.1414.7412.6699.09
Kapingamarangi8.199.279.849.159.2711.4313.6412.0813.7814.158.139.93145.85
Koror11.8411.3911.1610.188.567.447.3211.8317.4818.5313.5011.77152.90
Kosrae10.9413.8316.1116.6712.9316.0617.5117.7514.6414.9114.2214.22213.87
Kwajalein11.1811.286.663.162.642.355.266.726.939.879.7410.7490.41
Lukonor11.329.0811.278.418.939.2611.3111.6911.6515.9314.0410.15151.36
Majuro12.7313.4411.397.746.886.589.4210.1111.0111.1711.6911.17125.25
Pago Pago9.2610.1412.8413.3412.0010.689.399.665.335.555.386.53125.57
Pohnpei15.2714.8316.0813.189.5513.1718.4119.9614.8115.4314.2612.55182.36
Saipan10.625.613.852.532.591.892.632.383.628.9113.1310.0970.25
Yap12.188.838.516.395.194.565.637.8512.0415.0814.8213.50120.31

SPI values for seven time periods for Pacific Islands, computed by the Honolulu NWS office.
SPI values for seven time periods for Pacific Islands

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State/Regional/National Moisture Status
A detailed review of drought and moisture conditions is available for all contiguous U.S. states, the nine standard regions, and the nation (contiguous U.S.):

States
alabama arizona arkansas california colorado connecticut
delaware florida georgia idaho illinois indiana
iowa kansas kentucky louisiana maine maryland
massachusetts michigan minnesota mississippi missouri montana
nebraska nevada new hampshire new jersey new mexico new york
north carolina north dakota ohio oklahoma oregon pennsylvania
rhode island south carolina south dakota tennessee texas utah
vermont virginia washington west virginia wisconsin wyoming

Regional
northeast u. s. east north central u. s. central u. s.
southeast u. s. west north central u. s. south u. s.
southwest u. s. northwest u. s. west u. s.

National
Contiguous United States

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Drought Indicators
The following indicators illustrate the drought conditions this month:

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Contacts & Questions
For additional, or more localized, drought information, please visit:

Global Snow & Ice

Sea Ice Extent

According to the National Snow and Ice Data Center (NSIDC), the Northern Hemisphere sea ice extent — which is measured from passive microwave instruments onboard NOAA satellites — averaged for September 2012 was 3.61 million square km (1.39 million square miles), 48.7 percent below average. This was the smallest September sea ice extent in the 1979-2012 period of record. The previous smallest September Arctic sea ice extent occurred in 2007, at 4.3 million square km (1.66 million square miles). The six lowest September sea ice extents have occurred since 2007. This marks the 16th consecutive September and 136th consecutive month with below-average Arctic ice extent. Ice coverage was below average across all regions of the Arctic, except the East Greenland Sea, where the ice extent was near average. September Northern Hemisphere sea ice extent has decreased at an average rate of 13.0 percent per decade.

On September 16th, the Northern Hemisphere sea ice extent dropped to 3.41 million square kilometers (1.32 million square miles) reaching its annual minimum before beginning its annual growth cycle. The 2012 annual minimum extent was 760,000 square kilometers (293,000 square miles) below the previous record minimum, which occurred on September 18, 2007 and 49 percent below the 1979-2000 average. During the Arctic sea ice melt season, between March 20th, when the annual maximum extent occurred, and September 16th, 11.83 million square kilometers (4.57 million square miles) of ice was lost. This marks the largest seasonal Arctic sea ice loss in the satellite record, surpassing the 10.65 million square kilometers (4.11 million square miles) of ice loss during the 2008 melt season.

Animation of 2012 Arctic Ice Melt


Video provided by NOAA's Environmental Visualization Laboratory

September's PIOMAS Arctic Ice Anomaly
Sea Ice Volume Anomlay
Source: UW's Polar Ice Center

When using Arctic sea ice extent to monitor the state of sea ice conditions across the Arctic, no information is available on the thickness of the ice. To compensate for this, the Polar Science Center at the University of Washington developed a modeled dataset to measure the volume of Arctic sea ice using the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS). Sea ice volume is an important climate indicator because it depends on both ice thickness and extent and therefore more directly tied to climate forcing than extent alone. According to this dataset, Arctic sea ice volume reached a monthly low value during September 2012, at 3,400 km3, the smallest monthly sea ice volume on record. The previous record small Arctic sea ice volume for September occurred in 2011 at 4,200 km3. The September 2012 value is 72 percent lower than the mean over 1979-2011 period, 80 percent lower than the maximum in 1979, and 2.0 standard deviations below the 1979-2011 trend.


The September 2012 Southern Hemisphere sea ice extent was 19.39 million square km (7.48 million square miles), 3.51 percent above average and the largest September sea ice extent in the 1979-2012 period of record. Antarctic sea ice extent during September has increased at an average rate of 0.9 percent per decade, with substantial interannual variability.

The Southern Hemisphere sea ice extent reached its annual maximum extent on September 26th at 19.44 million square km (7.51 million square miles). This marked the largest annual maximum extent of Antarctic sea ice extent on record and surpassed the previous record of 19.36 million square km (7.47 million square miles) which occurred on September 21, 2006.

Arctic summer sea ice is shrinking much more rapidly than the rate at which Antarctic winter sea ice is expanding. Over the 1979-2012 record, the Arctic has experienced significant ice loss, while the growth of Antarctic sea ice has been slight. The September 2012 record low Arctic sea ice extent was 6.2 standard deviations below its 1979-2000 average, while the record large Antarctic sea ice extent was 2.1 standard deviations above its 1979-2000 average. Differences in hemispheric weather patterns, ocean currents, and geography partially account for these differing sea ice trends. A more detailed description of these differences is available through the NSIDC.

For further information on the Northern and Southern Hemisphere snow and ice conditions, please visit the NSIDC News page.

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Upper Air


Note: University of Alabama in Huntsville scientists advise that the AMSU channel 5 on the AQUA satellite, which has heretofore been the anchor-source of data in the construction of low- and mid-tropospheric temperatures (LT and MT) since 2002, was experiencing gradually increasing noise since 2009. However, a relatively rapid increase in noise in the recent few months to September 2012 generated clearly erroneous values. Therefore, beginning September 2012, these datasets (LT and MT) switched from AQUA to the AMSU channel 5 on NOAA-15 and NOAA-18, replacing AQUA data after 2009 in version 5.5.

Troposphere

Lower Troposphere

September Lower Troposphere
September Anomaly Rank
(out of 34 years)
Record Years Decadal Trend
°C °F Year °C °F °C °F
UAH +0.34 +0.61 Coolest 32nd 1984 -0.61 -1.10 +0.19 +0.34
Warmest 3rd 2010 +0.43 +0.77
RSS +0.27 +0.49 Coolest 30th 1984 -0.57 -1.03 +0.17 +0.31
Warmest 5th 2010 +0.40 +0.72
Year-to-Date Lower Troposphere
January–
September
Anomaly Rank
(out of 34 years)
Record Years Decadal Trend
°C °F Year °C °F °C °F
UAH +0.12 +0.22 Coolest 25th 1984 -0.32 -0.58 +0.13 +0.24
Warmest 10th 1998 +0.50 +0.90
RSS +0.09 +0.16 Coolest 24th 1985 -0.38 -0.68 +0.14 +0.24
Warmest 11th 1998 +0.53 +0.95

Mid-troposphere

September Mid-troposphere
September Anomaly Rank
(out of 34 years)
Record Years Decadal Trend
°C °F Year °C °F °C °F
UAH +0.21 +0.38 Coolest 29th 1984 -0.56 -1.01 +0.12 +0.21
Warmest 6th 2010 +0.39 +0.70
RSS +0.24 +0.43 Coolest 29th 1984 -0.56 -1.01 +0.14 +0.25
Warmest 6th 2010, 1998 +0.40 +0.72
UW-UAH +0.28 +0.50 Coolest 30th 1984 -0.67 -1.21 +0.19 +0.34
Warmest 5th 1998 +0.50 +0.90
UW-RSS +0.31 +0.56 Coolest 30th 1984 -0.63 -1.13 +0.19 +0.34
Warmest 4th 1998 +0.50 +0.90
Ties: 2005
Year-to-Date Mid-troposphere
January–
September
Anomaly Rank
(out of 34 years*)
Record Years Decadal Trend
°C °F Year °C °F °C °F
UAH -0.03 -0.05 Coolest 15th 1993, 1989 -0.25 -0.45 +0.04 +0.08
Warmest 20th 1998 +0.51 +0.92
RSS +0.03 +0.05 Coolest 20th 1985 -0.28 -0.50 +0.08 +0.15
Warmest 15th 1998 +0.52 +0.94
UW-UAH +0.03 +0.05 Coolest 18th 1984 -0.32 -0.58 +0.10 +0.18
Warmest 17th 1998 +0.61 +1.10
UW-RSS +0.09 +0.16 Coolest 23rd 1984 -0.33 -0.59 +0.13 +0.24
Warmest 11th 1998 +0.60 +1.08
Ties: 2011
RATPAC* +0.15 +0.27 Coolest 46th 1965 -0.85 -1.53 +0.15 +0.27
Warmest 10th 2010 +0.57 +1.03

*RATPAC rank is based on 55 years of data

Stratosphere

September Stratosphere
September Anomaly Rank
(out of 34 years)
Record Years Decadal Trend
°C °F Year °C °F °C °F
UAH -0.36 -0.65 Coolest 10th 1996 -0.61 -1.10 -0.40 -0.72
Warmest 25th 1991 +1.64 +2.95
RSS -0.32 -0.58 Coolest 8th 1996 -0.53 -0.95 -0.29 -0.53
Warmest 26th 1991 +1.51 +2.72
Ties: 2003
Year-to-Date Stratosphere
January–
September
Anomaly Rank
(out of 34 years)
Record Years Decadal Trend
°C °F Year °C °F °C °F
UAH -0.44 -0.79 Coolest 3rd 1996 -0.47 -0.85 -0.35 -0.64
Warmest 32nd 1992, 1983 +1.01 +1.82
RSS -0.43 -0.77 Coolest 1st 2012 -0.43 -0.77 -0.29 -0.51
Warmest 34th 1992 +0.99 +1.78

Background Information

Temperatures above the Earth's surface are measured within the lower troposphere, middle troposphere, and stratosphere using in-situ balloon-borne instruments (radiosondes) and polar-orbiting satellites (NOAA's TIROS-N). The radiosonde and satellite records have been adjusted to remove time-dependent biases (artificialities caused by changes in radiosonde instruments and measurement practices as well as changes in satellite instruments and orbital features through time). Global averages from radiosonde data are available from 1958 to present, while satellite measurements date back to 1979.

The mid-troposphere temperatures are centered in the in the atmospheric layer approximately 3–10 km [2–6 miles] above the Earth's surface, which also includes a portion of the lower stratosphere. (The Microwave Sounding Unit [MSU] channel used to measure mid-tropospheric temperatures receives about 25 percent of its signal above 10 km [6 miles].) Because the stratosphere has cooled due to increasing greenhouse gases in the troposphere and losses of ozone in the stratosphere, the stratospheric contribution to the tropospheric average, as measured from satellites, creates an artificial component of cooling to the mid-troposphere temperatures. The University of Washington (UW) versions of the UAH and RSS analyses attempt to remove the stratospheric influence from the mid-troposphere measurements, and as a result the UW versions tend to have a larger warming trend than either the UAH or RSS versions. For additional information, please see NCDC's Microwave Sounding Unit page.

The radiosonde data used in this global analysis were developed using the Lanzante, Klein, Seidel (2003) ("LKS") bias-adjusted dataset and the First Difference Method (Free et al. 2004) (RATPAC). Additional details are available. Satellite data have been adjusted by the Global Hydrology and Climate Center at the University of Alabama in Huntsville (UAH). An independent analysis is also performed by Remote Sensing Systems (RSS) and a third analysis has been performed by Dr. Qiang Fu of the University of Washington (UW) (Fu et al. 2004)** to remove the influence of the stratosphere on the mid-troposphere value. Global averages from radiosonde data are available from 1958 to present, while satellite measurements began in 1979.

References

Wildfires

Updated: 05 October 2012


Overview

Dry conditions coupled with an abundance of dry fuels contributed to the widespread extent of wildfire activity along the West Coast, the Northwest, and northern Rockies during September. The monthly average fire size reached 288.6 acres per fire — which was the 2nd highest for any September in the 2000-2012 record, second to September 2006, which had 307 acres per fire. Moreover, the year-to-date average fire size of 182.4 acres was the most since 2000 for any January through September period. The monthly total of 1.08 million acres burned by wildfires ranked as the 3rd highest for any September since 2000, while the year-to-date total acreage burned of 8.80 million acres was the 2nd highest since 2000. (The highest year-to-date total acreage burned was 9.07 million acres for the January through September period of 2006.) The monthly total number of 3,734 fires was the 2nd least for September in the thirteen-year record. Moreover, the year-to-date total number of fires was 48,258 fires and the least number since 2000 for any January through September period. Thus, the tendency of fewer fires — but larger in size — was denoted.

1-Month Wildfire Statistics*
September Totals Rank
(out of 13 years)
Record 2000-2010
Average
Value Year
Acres Burned 1,077,766 3ʳᵈ Most 1,474,795 2006 635,705
11ᵗʰ Least
Number of Fires 3,734 12ᵗʰ Most 13,598 2010 6,807
2ⁿᵈ Least
Acres Burned per Fire 288.6 2ⁿᵈ Most 307.0 2006 99.5
12ᵗʰ Least
Year-to-Date Wildfire Statistics*
January–September Totals Rank
(out of 13 years)
Record 2000-2010
Average
Value Year
Acres Burned 8,802,721 2ⁿᵈ Most 9,074,358 2006 6,031,095
12ᵗʰ Least
Number of Fires 48,258 13ᵗʰ Most 83,752 2006 65,980
Least on Record
Acres Burned per Fire 182.4 Most on Record 182.4 2012 91.1
13ᵗʰ Least

*Data Source: The National Interagency Fire Center (NIFC)

Discussion

Throughout September, exceptional drought (D4) was concentrated over the central Great Plains, firmly gripping parts of Nebraska, Kansas, the western half of Oklahoma, and the southeastern corner of Colorado, according to the October 2, 2012, U.S. Drought Monitor. Areas of extreme to exceptional drought combined with above-average temperatures and wind events to produce large wildfires occurrences in Nebraska, South Dakota, Wyoming, Colorado, and Oklahoma during the month. Drought conditions expanded over North Dakota and northwestern Minnesota, which coincided with wildfire activity during September. The states of Montana, North Dakota, South Dakota, and Minnesota experienced the driest September on record since 1895. Above-normal precipitation fell across much of the Southeast and Gulf Coast regions as well as parts of the Southwest and southern Great Basin. The rainfall most notably eased conditions from extreme to exceptional drought into severe drought (D2) across Arkansas, Missouri, Illinois, and Indiana. Surface and root moisture rebounded in the south central and southwestern states, yet underground aquifers remained in severe drought. Hot and dry conditions in Washington and central Idaho combined with low humidity and convectively active weather to trigger extreme fire behavior. A cold front the last week of September brought thunderstorms and showers to parts of Great Basin, and northern and central Rockies, giving moderate relief to the wildfire incidents, where the states of California, Nevada, Utah, Idaho, and Wyoming experienced much-above-normal warmth during September. Please see the U.S. temperature and precipitation report for additional information.

Significant Events


Please note, this is a list of select fires that occurred during September. Additional fire information can be found through Inciweb.


Areas from central Idaho across the northern High Plains experienced wildfire activity throughout September, while numerous fires developed in the Cascade Mountain Range at mid-month. Large fires in Washington and Oregon drew upon close to 3,500 personnel, with another 800 Northwest firefighters deployed to fires in Idaho, California, and Montana. More than 100 Canadian elite firefighters provided reinforcement as part of the Northwest Wildland Fire Protection Agreement to battle a widespread outbreak of wildfires following a severe lightning event. Following several months of continuous firefighting efforts, the U.S. resources were increasingly strained to cover the extent created by the new surge in fires. Smoke from the fires continued to contribute to air quality concerns for the Northwest. Oregon's Willamette Valley residents experienced hazardous levels of air quality at mid-month, clearing by September 24th after light rains and cooler weather approached. Air Quality Index alerts reached purple for Idahoans in late September and a state-wide burn ban was in effect.

Idaho

Wildfires were concentrated in the beetle-killed forest lands of Idaho. Two large fires burning since late July were active through September. Rain falling late in the month boosted containment to 45 percent of the Mustang Complex as of October 1st, after charring more than 339,000 acres in the Bitterroot Mountains of Idaho and Montana, during which at least eight injuries resulted. Prognosis remained good for the black bear cub, a survivor of the Mustang Complex given refuge at the Snowden Wildlife Sanctuary, following rescue and veterinary treatment of severely burned paws by the Idaho Fish and Game's Wildlife Services in late August. The Halstead Fire continued to rage, having consumed nearly 180,000 acres of mixed conifer (pine, spruce, and fir) timber stands at higher elevations, and scattered pines and sage grass along the steep slopes of Salmon River Canyon, at month's end. The estimated suppression costs for the Mustang Complex and Halstead Fire incidents exceeded $36 million and $26 million U.S. dollars, respectively, through September. The Trinity Ridge Fire, ignited on August 3rd in the Boise National Forest, reached 75 percent containment as of October 1st, with some areas remaining closed to ensure public safety. The McGuire Complex (comprised of two fires, Bagley and Herman), which threatened rural communities and over 300 structures, burned over 42,000 acres in September. During the early stages of this fierce blaze, battled by U.S. Forest Service "hotshot" teams, residents of the Orogrande, Dixie, and Comstock communities were evacuated, according to media accounts. Suppression costs were estimated at over $19 million U.S. dollars in September and the wildfire was at 20 percent containment as of October 1st.

Washington

The Highway 141 Fire originated on September 5th to quickly spread through over 1,600 acres of mixed timber, brush, and grass around the Columbia River Gorge, and threatened close to 500 residences, of which 45 homes were temporarily evacuated in Klickitat County. A few days later on September 9th, the Cascade Creek Fire flared from lightning in the Gifford Pinchot National Forest. During September, the wildfire consumed nearly 17,000 acres of beetle-killed timber, while forcing evacuation of numerous trails and campgrounds, where two vehicles burned. U.S. Forest Service firefighters saved the historic Gotchen Guard Station near Mount Adams from flames by using an aluminized structure wrap on the small ranger station that has stood since 1909.

Dry lightning strikes ignited at least 80 wildfires fires across the Pacific Northwest during September 8th–9th, with Oregon receiving 41 strikes while Washington received over 3,300 strikes, according to media reports. A wildfire incident in central Washington, the Wenatchee Complex, consisted of at least 16 smaller wildfires and threatened up to 850 homes. One firefighter died as a result of efforts to contain the blaze, which consumed over 55,000 acres of timber, brush, and grass during September. The estimated suppression costs of the fire neared $28 million U.S. dollars.

Strong winds during September 10th–11th dramatically fanned the flames of the lightning-sparked Barker Canyon Complex fire which consumed over 90,000 acres of dry brush and sage near the Grand Coulee Dam during September. The wildfire destroyed 3 homes, up to 9 outbuildings, 2 power stations near the dam, and forced evacuation of over 75 residents, according to media reports. Since September 16th, the Goat Fire burned over 7,000 acres along rugged, rocky cliffs near Alta Lake in north central Washington. Local television was lost when the wildfire damaged the KSPS-TV station's antenna receiver and threatened other critical communications sites as well as about 80 homes.

Canadian firefighting forces supported four fires in Washington, including the Table Mountain Fire, the Wenatchee and Okanogan complexes, and the Goat Fire — each of which remained active at month's end.

Oregon

The Pole Creek wildfire, which charred over 26,000 acres of dead timber and understory (juniper, sage, and bitterbrush) near Sisters, Oregon, started on September 9th. The blaze burned four cars along the Pole Creek trailhead, as search teams located and helped in evacuation efforts of campers and hikers within the wilderness area. Notably, the wildfire impacted air quality for residents as nightly inversions trapped the smoke in the valley. The American Red Cross provided shelter at a local school where the air was filtered. About 6 mm (one-quarter inch) of rain falling over September 22nd–23rd helped to limit the fire's spread. Characterized as primarily an "underburn", the fire did not permanently ruin the forest. Rather, U.S. Forest Service officials cited forest thinning and fire treatment projects in recent years as having greatly mitigated the fire's impact closest to the residential community, according to media reports.

Montana

Over 8,000 acres of beetle-killed timber were consumed during September by the Pine Creek Fire in southern Montana. Five homes and several outbuildings were lost in late August when the wildfire originated. The fire swept quickly up steep, inaccessible terrain of wilderness in Gallatin National Forest, containing very dry duff and woody fuels. The fire was estimated to be 51 percent contained as of October 5th. Another Gallatin National Forest wildfire, the lightning-sparked Millie Fire, scorched over 10,000 acres as the dry understory facilitated burning of the younger, regenerated forested stands. Estimated suppression costs of the fire exceeded $10 million U.S. dollars as of the end of September.

Monthly Wildfire Conditions

Wildfire information and environmental conditions are provided by the National Interagency Fire Center (NIFC) and the U.S. Forest Service (USFS) Wildland Fire Assessment System (WFAS).

Wildfires sparked by lightning in Nebraska's panhandle during late August were bolstered by strong canyon winds to spread quickly through dry fuels (timber and grasses), with the flames tripling in extent from September 1th–2nd. Firefighting efforts proved difficult in the rugged forest terrain of northwestern Nebraska and the bordering area of South Dakota, which accommodates a diverse range of outdoor recreation (hunting, fishing, hiking, and bird-watching). The estimated suppression costs for the wildfires topped $3.2 million U.S. dollars, according to media reports. The fires coincided closely with areas of dangerously low fuel moistures (below 10 percent) for all observed intervals of the 10-hour, 100-hour, and 1000-hour fuel moistures. The Region 23 Complex — which consisted of two Nebraskan wildfires, the West Ash and Douthit — consumed over 86,000 acres to become the largest and most destructive in the state's history, according to media accounts. About 400 residents were evacuated near Chadron and Whitney. Burning ponderosa pines exploded, shooting flames up to 90 m (295 ft) and entirely killing many of the old growth trees. Although some of the native wildlife perished in the flames, the loss of canopy may potentially improve the habitat for bighorn sheep and attract new bird species. The wildfire complex was fully contained by September 11th. Meanwhile, another large wildfire that burned nearby, the Wellnitz Fire, and later crossed into South Dakota's Pine Ridge Indian Reservation, scorched over 77,000 acres between August 29th–September 7th. At least 10 homes and more than 50 structures within the two states were damaged by the fires, with two of the homes being located in Slim Buttes, South Dakota.

In southern California, the Williams Fire consumed over 4,000 acres of chaparral within the Angeles National Forest, an area of extreme moisture deficits as indicated by the Keetch-Byram Drought Index (KBDI) value in excess of 700 units. The dense brush, up to 20 years old, over rugged terrain posed a challenge to firefighting efforts, according to media reports. On September 2nd, nearly 12,000 visitors in the campgrounds were evacuated to clear access of the single road into the San Gabriel Canyon for use by fire trucks and emergency vehicles. The wildfire was fully contained as of September 13th.


A couple of large wildfires developed in Wyoming and the Dakotas at mid-month. The low 10-hour fuel moisture (under 5 percent) expanded dramatically northeastward from the Great Basin into the Great Plains. The 100-hour fuel moisture lessened over central Idaho through western Montana, dropping under 6 percent. Across the western third of the nation, the 1000-hour fuel moistures remained at or below 10 percent through the first half of September, with the exception of central Arizona.

Large fires in Wyoming coincided closely with the extremely low 10-hour fuel moisture (under 2 percent) centered over the state on September 15th. The Horsethief Canyon Fire caused disruption for many people visiting the Jackson Hole ski resort area to attend the state's annual Fall Arts Festival, where up to 1,600 residents faced potential evacuation. The blaze which raged through more than 3,000 acres of towering trees, sagebrush, and grasslands between September 8th and early October. On September 9th, the Sheep Herder Hill Fire resulted in the evacuation of nearly 500 residents near Casper, Wyoming. Gusty winds quickly spread its flames through fuels of fallen beetle-killed timbers (fir and pine) and sage, as the blaze exceeded 15,500 acres of difficult terrain prior to being fully contained by September 18th.

An area of 1000-hour fuel moisture remained below 6 percent in northern Nevada and the bordering edges of California, Idaho, and Oregon for most of the month. The Bagley Fire, which was sparked by lightning in northern California on August 18th, consumed over 46,000 acres of conifer, brush, and hardwood stands by mid-September. Deeply embedded heat within thick duff, stump holes, and large stationary fuels emitted smoke within the fire's interior. Sediment run-off into the McCloud River was a concern during the fire's suppression efforts.


The Shockey Fire, which ignited September 23rd in southern California, claimed one life, destroyed 20 homes, and damaged 15 others, according to media accounts. The American Red Cross established an evacuation shelter for residents. Damaged utility lines resulted in power outage for over 100 households.

Several wildfires developed in western North Dakota in the latter part of September as warm, dry conditions and low humidity contributed to extreme fire weather behavior. The Little Swallow Fire burned about 10,000 acres of the Berthold Indian Reservation between September 19th–25th. The Cottonwood Creek Fire, near the Theodore Roosevelt National Park, charred nearly 600 acres of juniper, sage, and short grass between September 21th–28th. Smoke-jumpers and a water-dropping helicopter assisted in battling the wildfire in the rugged badlands terrain, according to media reports. Some campground evacuations were imposed.

A couple of wildfires in Alaska prolonged the ending for the state's fire season. Strong, northeasterly winds rekindled the Dry Creek Fire in late August, and winds during September spread its flames over an additional 6,600 acres near the Tanana River. Its smoke impacted the air quality for residents of Fairbanks for a second time in the latter part of September, as the lightning-sparked wildfire scorched in excess of 47,000 acres since June 23rd. Meanwhile to the southeast of Fairbanks, the wind-driven Industrial Park wildfire blazed close to 6,000 acres of grass land from September 25th–28th.


All Fire Related Maps


Citing This Report

NOAA National Climatic Data Center, State of the Climate for September 2012, published online October 2012, retrieved on September 19, 2014 from http://www.ncdc.noaa.gov/sotc/2012/9.