Entire Report - October 2011


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:



October Extreme Weather/Climate Events
  • Climate Highlights — October
  • During October, a persistent upper-level weather pattern brought below-normal temperatures to the southeastern United States and above-normal temperatures from the Southwest, across the northern tier of the United States, and into parts of the Northeast. Near-normal precipitation during October across the Southern Plains made little change in long-term drought conditions.
  • The average U.S. temperature in October was 55.7 degrees F, 0.9 degrees F above the 1901-2000 long term average. Precipitation, averaged across the nation, was 2.04 inches. This was 0.07 inch below the long-term average, with variability between regions. This monthly analysis is based on records dating back to 1895.
  • The Southwest, states along the U.S.-Canadian border, and much of the Northeast experienced above-normal temperatures. Eighteen states in total had October temperatures above their long-term averages.
  • Eleven states from Louisiana to West Virginia had October temperatures below their long-term averages. Meanwhile, states in the Pacific Northwest, the Central and Southern Plains, and parts of the Midwest had October temperatures near average.
  • An early season storm brought heavy snow accumulations to the northeastern United States on October 29th–31st. Several locations broke October snow storm records, including New York City’s Central Park, where 2.9 inches of snow accumulated. The highest snowfall amounts were further inland, with over 30 inches accumulating in western Massachusetts and southern New Hampshire. The heavy, wet snow falling on the autumn foliage, combined with strong winds, caused havoc across the region and over 3 million people lost power. The storm received a preliminary rank of Category 1 on the Northeast Snowfall Impact Scale (NESIS), which takes into account snowfall accumulation in populated areas, the only ranking storm on record to occur during October.
  • Several storms impacted the interior western states during October, bringing above-normal precipitation totals to Idaho, Montana, Nebraska, Nevada, and Wyoming. Storms also impacted the eastern seaboard, causing wetter-than-normal conditions in Florida and the Northeast.
  • A string of states from Minnesota, southward along the Mississippi River, to Louisiana observed below-normal precipitation. Eight states were drier than normal during October, with Iowa, Louisiana, and Missouri each having their ninth driest October on record.
  • Dry and warm weather conditions the first few weeks of October created ideal wildfire conditions across the Great Basin and Pacific Northwest, contributing to record acreage burned during the month. Over half a million acres burned nationwide during October — more than double the long-term average.
  • As of November 1st, about nine percent of the contiguous United States remained in the worst category of drought, called D4 or exceptional drought. The footprint was smaller than the nearly 12 percent of the country experiencing exceptional drought at the beginning of October. Slight improvement of drought conditions occurred across the Southern Plains during October, where near-normal precipitation was observed. The drought stricken areas of the Southern Plains would need at least 18 inches of rain in a single month to end the on-going drought.
  • A list of select October temperature and precipitation records can be found here.
  • Climate Highlights — August-October (3-month period) and Year-to-Date period
  • During the August-October period, the United States, as a whole, experienced much-above-normal temperatures with the nationally averaged temperature of 66.0 degrees F ranking as the 10th warmest August-October on record.
  • This same three month period brought very warm temperatures to the western half of the country, where 10 states experienced temperatures among their 10 warmest for the period, including Texas, which was record warm. The Northeast was also particularly warm, where eight states had a top 10 warm August-October. Below-normal temperatures were present for parts of the Ohio Valley and Gulf Coast.
  • Precipitation was a mixed bag during the August-October period, with record wet conditions across the Northeast, and much drier than normal conditions across the central United States. Maryland, New Jersey, New York, Pennsylvania, and Vermont had a record wet August-October period, and seven other states in the region had precipitation totals among their 10 wettest.
  • For the first 10 months of 2011, the contiguous United States was warmer than average. Above-normal temperatures were present across the southern tier of the country and along the eastern seaboard. Texas was record warm for the 10 month period, while Delaware, Maryland, New Jersey, New Mexico, and Oklahoma had temperatures ranking in their top 10 warmest.
  • As a whole, the year-to-date period brought near-normal precipitation to the United States, but there was significant regional variability. States across the Northeast were record wet, including Connecticut, Massachusetts, New Jersey, New York, Ohio, Pennsylvania, and Vermont. Drier than normal conditions prevailed across the southern tier of the country, with record dry conditions reported for Texas.
  • The Regional Climate Extremes Index (RCEI), which is sensitive to extremes in temperature, rainfall, dry streaks, drought, and tropical cyclones, indicated that for the Northeast climate region an area over three times the average value was affected by extreme climate conditions for the year-to-date period. For the South Climate Region, the RCEI was more than twice the average value. The values both represented the second highest values for the January-October period, regionally. For the Northeast, contributing factors included warm minimum temperatures, wet Palmer Drought Severity Index (PDSI), days with precipitation and 1-day precipitation totals. For the South, warm maximum temperatures and dry PDSI values contributed to the high RCEI value.

Alaska Temperature and Precipitation:

  • Alaska had its 31st warmest October on record, with a temperature 2.38°F (1.32°C) above the 1971–2000 average.
  • Alaska had its 33rd warmest August-October on record, with a temperature 0.84°F (0.47°C) below the 1971–2000 average.
  • Alaska had its 36th warmest year-to-date period on record, with a temperature 0.29°F (0.16°C) above the 1971–2000 average.
  • Alaska had its 5th driest October since records began in 1918, with an anomaly that was 33.2 percent below the 1971–2000 average.
  • Alaska had its 38th wettest August-October on record, with an anomaly that was 4.8 percent above the 1971–2000 average.
  • Alaska had its 33rd driest year-to-date period on record, with an anomaly that was 1.3 percent below the 1971–2000 average.

For additional details about recent temperatures and precipitation across the U.S., see the Regional Highlights section below. 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)
  • The Northeast averaged warmer than normal for the 7th consecutive month. October’s average was 50.7 degrees F (10.4 degrees C), which was 1.3 degrees F (0.61 degrees C) above normal and 0.4 degrees F (0.22 degrees C) warmer than October 2010. It was the warmest October since 2007. Unlike the previous three months, not all the states were warmer than normal. Maryland and West Virginia had temperatures that averaged -0.8 degrees F (-0.44 degrees C) and -1.2 degrees F (-0.67 degrees C), respectively. Departures among the other ten states in the region ranged from +0.4 degrees F (+0.22 degrees C) in Pennsylvania to +3.5 degrees F (+1.94 degrees C) in Maine. It is interesting to note that Vermont had its 19th warmest October in 117 years while West Virginia saw its 35th coolest October since 1895.
  • After a wet August and September, the Northeast began to dry out when high pressure settled over the region around the 5th of October. A string of lovely fall days around the Columbus Day holiday weekend brought tourists back to flood-ravaged areas in New England for fall foliage viewing on the traditional leaf peeping weekend. Unsettled weather returned, with a series of rain events and even a major snowstorm during the second half of October. The end result was above normal precipitation in the Northeast for the third month in a row. The region’s average of 4.83 inches (122.7 mm) was 126 percent of normal. It was the 20th wettest October since 1895. Delaware was the only state with below normal precipitation, at 85 percent of normal. The rest of the states saw departures that ranged from 104 percent of normal in Vermont to 166 percent of normal in Rhode Island. It was the 8th wettest October since 1895 in Massachusetts and the 10th wettest in New Hampshire and Rhode Island. October was the 7th month since January with wetter than normal precipitation the year-to-date total was 47.71 inches (1212 mm). This was 2.19 inches (55.6 mm) more than the region’s annual average and just 6.87 inches (174.5 mm) less than the wettest complete year on record, 1996. If the Northeast tallies average precipitation totals for the next two months, 2011 will be the wettest year since 1895.
  • For the third time in three months, a major weather event impacted the Northeast region. After enduring a hurricane in August, and the remnants of a tropical storm in September, residents in parts of the Northeast had to deal with up to 30 inches (76.2 cm) of heavy, wet snow on October 29th and 30th. Trees still in leaf and even conifers succumbed to the weight of the snow, causing more tree damage and power outages than Hurricane Irene did in August. About 3 million customers, from the central Appalachians of West Virginia to southern Maine, lost power. Some still were in the dark a week later due to the complexity of the restoration effort and the areal coverage of the outages. Tree and branch removal by state and local authorities had to be coordinated with crews from the various power companies. Out-of-state power crews were brought in before and after the event to help with the restoration. One power company in Connecticut expected the cost of the restoration and cleanup from the storm to be about $100 million. Connecticut’s insurance commissioner estimated the storm costs in the Nutmeg State to be upwards of $500 million, with regional totals estimated at over $1.0 billion. While the main impact of the storm was the damage to the power grid, the wintry weather also resulted in flight and rail cancellations or delays, caused many vehicular accidents and was responsible for at least 22 deaths in the Northeast. In addition, new daily and monthly snowfall records were set, including 13.6 inches (34.5 cm) on the 29th at Concord, NH, and 9.1 inches (23.1 cm) on the 29th at Scranton, PA. Concord, NH’s monthly total of 23.0 inches (58.4 cm) blew away their previous monthly record snowfall total of 2.1 inches ( 5.3 cm).
  • For more information, please go to the Northeast Regional Climate Center Home Page.
  • Midwest Region: (Information provided by the Midwest Regional Climate Center)
  • October precipitation varied considerably across the Midwest. The western half of the region received below normal precipitation while the eastern half received above normal precipitation. Totals ranged from less than 25% of normal in parts of Missouri and Iowa to more than 200% of normal in parts of Ohio.
  • October temperatures fluctuated throughout the month. Despite starting the month with a couple days of cold temperatures, the first half of the month was above normal on average. The second half of the month was below normal despite having a brief warm spell. On average, the month was near normal for much of Missouri, Illinois, Indiana, and Ohio. Kentucky had below normal temperatures ranging to 2°F (1°C) below normal. Iowa, Minnesota, Wisconsin, and Michigan were slightly above normal for the month with temperatures up to 5°F (3°C) above normal.
  • Drought conditions in October improved in eastern Illinois and western Indiana but further west there was expansion and intensification of drought. The small area of moderate drought at the beginning of the month in northern Iowa and southern Minnesota expanded and intensified to severe drought by the end of the month. By the end of the month roughly 20% of Illinois, 40% of Minnesota, 50% of Missouri, and 70% of Iowa were designated in drought.
  • Two strong low pressure systems brought strong winds to the Great Lakes. On the 14th and 15th, low pressure centered in Canada brought strong northwest winds to the Great Lakes. Wind and wave warnings were issued on the lakes and power outages were scattered across the upper Midwest. On the 19th and 20th another low moved across Ohio and brought strong northeast winds to the Great Lakes. Winds in the Chicago area topped 50 miles/hour (80 km/hour) with gusts exceeding 60 miles/hour (95 km/hour). In both Chicago and Milwaukee, boats anchored near shore were battered by the waves sinking or washing ashore dozens of boats. Both cities also had windows blown out of high-rise buildings by the strong winds.
  • With the Missouri River back in its banks, boat traffic resumed along the river for the first time since June in both Iowa and Missouri. Road repairs were also ongoing with several stretches of Interstate 29 in western Iowa and northwest Missouri reopened in early October. Scores of levees, weakened or breached by the flood waters, were in various stages of repair in both states.
  • For details on the weather and climate events of the Midwest, see the weekly summaries in the MRCC Midwest Climate Watch page.
  • Southeast Region: (Information provided by the Southeast Regional Climate Center)
  • Mean temperatures in October were between 1 and 4 degrees F (0.5 and 2.2 degrees C) below average across most of the Southeast region, except along coastal sections of North Carolina and Virginia. Monthly temperatures were generally above average across Puerto Rico and the U.S. Virgin Islands. It was the coldest October ever observed at the summit of Mount Mitchell, NC in a record extending back to 1980. Across the Southeast, there were over 180 daily minimum and over 300 daily low maximum temperature records tied or broken during the month. Most of these records occurred in the wake of several cold frontal passages. Dulles Airport near Washington D.C. recorded a maximum temperature of 39 degrees F (3.9 degrees C) on the 29th of the month following a rare October snowstorm, making it the lowest maximum October temperature ever recorded in a record extending back to 1962.
  • Precipitation was highly variable across the Southeast in October. Monthly totals were at least 150 percent of normal across the Florida Peninsula, with some locations exceeding 300 percent of normal. Strong storms from the 7th to the 10th of the month dropped up to 17 inches (431.8 mm) of precipitation across central and southern Florida. It was the second wettest October on record in Vero Beach, FL, which recorded 21.93 inches (557.0 mm) for the month. Key West, FL recorded 17.14 inches (435.4 mm), making it the fourth wettest October on record. Most of this precipitation occurred over a 5-day period from the 15th to the 19th of the month. Significant flooding and property damage were reported. In contrast, October was unusually dry across most of Puerto Rico and the U.S. Virgin Islands. St. Thomas recorded just 1.95 inches (49.5 mm) of precipitation for the month, which was nearly 3.5 inches (88.9 mm) below average. The driest locations across the Southeast (less than 25 percent of normal) were found across Alabama and northwest Florida. Mobile, AL recorded just 0.09 inches (2.3 mm) of precipitation for the month. Elsewhere across the region, monthly precipitation was near normal to slightly above normal. A rare October snowstorm dumped up to 7 inches (177.8 mm) of snow across northern Virginia from the 28th to the 29th of the month, while higher elevations across the Southern Appalachians recorded up to 2 inches (50.8 mm). Dulles Airport recorded just its third measurable October snowfall ever with 0.6 inches (15.2 mm). On the 2nd of the month, Beech Mountain, NC recorded 0.5 inches (12.7 mm) of snow, making it the earliest measurable autumn snowfall on record in North Carolina.
  • There were 84 reports of severe weather across the Southeast in October, including 12 confirmed tornadoes. On the 9th of the month, an EF-1 tornado caused extensive damage to several homes on Fleming Island near Jacksonville, FL. A small outbreak of weak tornadoes occurred across eastern Virginia on the 13th of the month. Two of these tornadoes were caught on video by motorists as they crossed Interstate 95 and Highway 1 in Stafford and Prince William Counties. An EF-1 tornado damaged over 30 homes in a subdivision near Kent Lake, VA, while another EF-1 tornado in Louisa County caused major damage to the historic Sylvania Plantation house, which was built in 1746. The most severe tornado was an EF-2 that struck the Sunrise/Plantation area in Broward County, FL on the 18th of the month. This tornado caused damage to as many as 50 homes and several minor injuries were reported.
  • There were relatively few changes to the Drought Monitor in October. Extreme drought (D3) conditions continued across much of Georgia, eastern portions of Alabama, the upstate of South Carolina, and the western panhandle of Florida. There was a slight improvement from extreme (D3) to severe drought (D2) across parts of central and southern Georgia, while drought conditions were completely eliminated across most of the Florida Panhandle. Drought conditions expanded across Alabama, where precipitation deficits were the greatest.
  • 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)
  • The High Plains Region experienced a wide range of weather conditions this October including record warmth, record cold, severe storms, and snow. Overall, temperature departures generally ranged from near normal in the south up to 8.0 degrees F (4.4 degrees C) above normal in the north. Many locations across North Dakota ranked in the top 10 warmest Octobers on record. Fargo, North Dakota’s average temperature was 52.6 degrees F (11.4 degrees C) this month which was 7.3 degrees F (4.1 degrees C) above normal. That was warm enough to be ranked as the 6th warmest October on record (period of record 1881-2011). The warmest October on record, which was set in 1963, held firmly at 57.2 degrees F (14.0 degrees C). The hot, dry, and windy start to the month contributed to the warm average temperatures and also created dangerous fire weather conditions. Temperatures reached the mid to upper 90s throughout the Region and new daily temperature records were set in the Dakotas. One impressive record occurred at Dunn Center 1E, North Dakota, which is located north of Dickinson. The high temperature on October 4 was 98.0 degrees F (36.7 degrees C) which smashed the old record of 87.0 degrees (30.6 degrees C) set in 1963 (period of record 1919-2011). On the other end of the spectrum, Laramie, Wyoming set a new daily low temperature record of -16.0 degrees F (-26.7 degrees C) on October 27 after receiving some fresh snow. The old record of 0.0 degrees F (-17.8 degrees C) was set in 1996 (period of record 1948-2011).
  • Precipitation was highly variable this month across the High Plains Region. Little precipitation fell in the eastern part of the Region, along the eastern sides of North Dakota, South Dakota, Nebraska, and Kansas. Some locations in these areas were ranked in the top 10 driest Octobers on record. Although the dryness led to the development of abnormally dry and moderate drought conditions, the dry weather did help harvesting activities progress as many days were suitable for fieldwork. By the end of the month, the harvesting of most row crops was either completed or nearing completion. Extremely dry conditions were present early in the month and numerous fires were reported in Nebraska and South Dakota. These fires destroyed crops, combines, center pivots, and even homes. One fire in Stapleton, Nebraska, which is north of North Platte, burned over 25,000 acres and caused around $4 million in damages.
  • Meanwhile, other areas of the Region received over 200 percent of normal precipitation. These areas included central Nebraska, northwestern Kansas, pockets of Colorado, and southeastern and northwestern Wyoming. October 6-8 was an eventful time frame for many parts of the Region. Severe weather, including tornadoes, high winds, and hail were reported across southwestern Kansas on the 7th. Meanwhile, northwestern Kansas received high precipitation, most of which fell during the October 6-8 time frame as a slow moving system passed through the area. By the end of the month, a few locations had even surpassed 300 percent of normal precipitation. An extreme example was Hoxie, Kansas which received 6.95 inches (177 mm) of precipitation, most of which fell during the October 6-8 time period. Despite the monthly total for Hoxie being 5.81 inches (148 mm) above normal, or an impressive 610 percent above normal precipitation, this was only the 3rd wettest October on record (period of record 1897-2011). The wettest October on record occurred in 1946 with 7.55 inches (192 mm).
  • Parts of Wyoming were also wetter than normal this month. North central and southeastern Wyoming both had precipitation totals which were at least 200 percent of normal. Several locations ranked in the top 10 wettest Octobers on record and with 3.72 inches (94 mm) of precipitation, Sheridan, Wyoming had its wettest October on record (period of record 1907-2011). This monthly total was 2.31 inches (59 mm) above normal or 264 percent of normal precipitation. 1.79 inches (45 mm) fell in one day, October 7, and a new daily precipitation record was set as well. The old record occurred in 1993 with only 0.59 inches (15 mm).
  • In addition to heavy precipitation and severe storms, some of the first snow of the season affected parts of the Region. An early snow storm caused problems in Colorado. Leaves were still on trees as heavy, wet snow fell on October 26. As a result, trees fell causing many power outages. Snow totals were highly variable across north central Colorado, but with 11.5 inches (29 cm) of snow, Boulder, Colorado set a new daily snow record for October 26 (period of record 1893-2011). This crushed the old daily record of 4.1 inches (10 cm) set in 2006.
  • For more information, please go to the High Plains Regional Climate Center Home Page.
  • Southern Region: (Information provided by the Southern Regional Climate Center)
  • Average temperatures varied spatially in the Southern Region. In Mississippi, southern Tennessee, and south eastern Louisiana, temperatures were generally 2 to 4 degrees F (1.11 to 2.22 degrees C) below normal. Much of Arkansas and the remainder of Louisiana experienced a slightly cooler than normal October, while in Oklahoma and Texas, temperatures averaged between 2 to 4 degrees F (1.11 to 2.22 degrees C) above normal. The state average temperatures were as follows: 60.50 degrees F (15.83 degrees C) in Arkansas, 65.30 degrees F (18.50 degrees C) in Louisiana, 60.90 degrees F (16.06 degrees C) in Mississippi, 61.50 degrees F (16.39 degrees C) in Oklahoma, 56.40 degrees F (13.56 degrees C) in Tennessee, and 66.80 degrees F (19.33 degrees C) in Texas. For Mississippi, it was the twelfth coldest October on record (1895-2011), while Louisiana recorded its twentieth coldest October on record (1895-2011). In Tennessee it was the eighteenth coldest October on record (1895-2011).
  • With the exception of central Texas and eastern Tennessee, the bulk of the Southern Region experienced a very dry October. In central Texas, stations averaged between 100 and 250 percent of normal precipitation for the month. It is worth noting that these stations received between 4 to 8 inches (101.60 to 203.20 mm) of precipitation for the month. In eastern Tennessee, stations averaged between 100 to 200 percent of normal precipitation, or approximately 3 to 6 inches (76.20 to 152.4 mm) for the month. By contrast, conditions were extremely dry in Louisiana, Mississippi, eastern Texas, and southern Arkansas. Stations in southern Louisiana and southern Mississippi averaged only between 0 to 25 percent of normal, or approximately 3 to 5 inches (76.20 to 127.00 mm) less than they normally receive for the month. Louisiana averaged only 0.82 inches (20.83 mm) for the month, making it their ninth driest October on record (1895-2011). For Mississippi, it was the seventeenth driest October on record with an average precipitation total of 1.10 inches (27.94 mm). Other state average precipitation totals for the month include: Arkansas with 2.48 inches (62.99 mm) of precipitation, Oklahoma with 2.67 inches (67.82 mm) of precipitation, Tennessee with 2.39 inches (60.71 mm) of precipitation, and Texas with 2.18 inches (55.37 mm) of precipitation.
  • Over the month of October, drought conditions did not change much from September in Mississippi, Tennessee and Arkansas. Conditions have changed, however; in Texas, Oklahoma and Louisiana. In Oklahoma, much of the central portion of the state did see a one category improvement from exceptional drought to extreme drought. This was also the case for central Texas, where rainfall for the month was abundant. In Louisiana, the south east parishes went from being drought free to moderate drought. In addition, much of the western part of the state is now experiencing exceptional drought. In total for the Southern Region, there was a decrease in exceptional drought from 53.77 percent areal coverage to 41.90 percent areal coverage.
  • October was a quiet month for severe weather in the Southern Region. Less than half a dozen twisters were reported and there was very little in the way of hail or strong winds. The biggest outbreak of severe weather occurred on October 22, 2011, with several hail reports in central Oklahoma. Softball sized hail was reported in Okfuskee County, and some windshields were shattered by hail in Canadian County.
  • The bulk of weather impacts for the Southern Region continue to pertain to the longstanding Texas drought. The effects of the drought and wildfires on Texas agriculture have been devastating. Cotton has been particularly hard hit with a loss of more than half of the 7.1 million acres planted this season. With prices being extremely high, cotton crop losses alone have translated into a $1.8 billion loss to the Texas cotton industry. Precipitation during the second half of October helped to replenish livestock tanks and ponds and helped with the plating of fall crops and winter forages, but much more additional precipitation will be needed to maintain growth. Additionally, Texas corn farmers were expected to only harvest about half of the normal 200 million bushels the state normally produces each year. The devastating wildfire season has been estimated to have caused $200 million in damage to Texas agriculture alone. Overall, the $5.2 billion in estimated 2011 losses to Texas agriculture set in August have only increased since this estimate was put forth (Information provided by the Texas Office of State Climatology).
  • For more information, please go to the Southern Regional Climate Center Home Page.
  • Western Region: (Information provided by the Western Regional Climate Center)
  • October saw a startup of the winter storm season and the 2011-2012 water year. The first such storm arrived during the early days of October, followed by another significant event about mid-month, and providing above normal precipitation for much of the West. Temperatures were near normal throughout most of the West, with areas of above normal temperatures throughout Montana, Wyoming, eastern California, Nevada, and southern Arizona.
  • The greatest positive temperature anomalies this October occurred in eastern Montana, northern Wyoming, and southern Arizona. Tucson’s October average was 83.3 F (28.5 C), the 13th warmest October on record. Billings, Montana experienced a monthly average of 51.9 F (11 C), the 9th warmest October since 1948. In the midst of warm October temperatures in the inland Northwest, record low temperatures on individual days were recorded with the passage of cold fronts. On October 27th Laramie, Wyoming had a record low of -16 F (-26.7 C), shattering the previous daily record of 7 F (-13.9 C) set in 1970.
  • Precipitation was near normal for most of the West, with pockets above normal. Many above normal values were recorded in the inland Northwest, setting or tying previous precipitation records. Missoula, Montana experienced its 4th wettest October on record with a rainfall total of 2.4 in (60.9 mm). Pocatello, Idaho and Boise, Idaho both experienced their 6th wettest Octobers on record with rainfall totals of 1.99 in (50.5 mm) and 1.79 in (45.5 mm) respectively. One of the most impressive records occurred at Riverton, Wyoming on October 8th. Riverton received a daily total of 1.14 in (29 mm) rainfall, well beyond the previous record for the date of 0.11 in (2.8 mm) set in 2010, and above the October monthly average at that location of 0.91 in (23 mm).
  • Western Oregon and southern Arizona and New Mexico were drier than normal at most stations. October 2011 was the 16th driest year on record at Eugene, Oregon airport, with a precipitation total of 1.81 in (46 mm), or 51% of the 3.54 in (90 mm) October average. Tucson, Arizona received 0.06 in (1.5 mm), only 7% of the average 0.87 in (22 mm) for that location, making it the 29th driest October on record at Tucson. The low precipitation in the Southwest allowed drought conditions and extent to persist for Arizona and New Mexico throughout October.
  • October 6-8: Winter Storm: The first winter storm of the 2011-2012 water year passed through the West October 6th through 8th, providing precipitation throughout the region and dropping 1 to 2 ft (30.5 cm-61.0 cm) of snow at some locations the Sierra and Rockies.
  • October 26, 27: Colorado Snowstorms: Heavy snowstorms dropped up to 18 in (45.7 cm) of snow in the foothills west of Denver, and 5-8 in (12.7 cm-20.3 cm) in the Denver metropolitan area. The heavy, wet snow felled many trees leaving 200,000 without power.
  • October (all month) Late first freezes: Warm temperatures dominated throughout the West in October. Many locations saw much later than average first freezes. Ely, Nevada experienced its first freeze October 5. The only later freeze at that location was October 13, 1963. Spokane, Washington and Boise, Idaho experienced their first freezes on October 25, more than two weeks later than their average freezes of October 8th and October 10th respectively.
  • 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:


October 2011 Selected Climate Anomalies and Events MapOctober 2011 Selected Climate
Anomalies and Events Map


Global Highlights

  • The combined global land and ocean average surface temperature for October 2011 was the eighth warmest on record at 14.58°C (58.14°F), which is 0.58°C (1.04°F) above the 20th century average of 14.0°C (57.1°F). The margin of error associated with this temperature is +/- 0.07°C (0.13°F).
  • Separately, the global land surface temperature was 1.10°C (1.98°F) above the 20th century average of 9.3°C (48.7°F), making this the second warmest October on record. The margin of error is +/- 0.11°C (0.20°F). Warmer-than-average conditions occurred across Alaska, Canada, most of Europe and Russia, and Mongolia. Cooler-than-average regions included the southeastern United States, most of southern and western South America, parts of Algeria and Libya, part of Eastern Europe, and far southeast Asia.
  • Separately, the global land surface temperature was 1.10°C (1.98°F) above the 20th century average of 9.3°C (48.7°F), making this the second warmest October on record. The margin of error is +/- 0.11°C (0.20°F).
  • The October global ocean surface temperature was 0.39°C (0.70°F) above the 20th century average of 15.9°C (60.6°F), making it the 11th warmest October on record. The margin of error is +/- 0.04°C (0.07°F). The warmth was most pronounced across the north central and northwest Pacific, the northeast Atlantic, and portions of the mid-latitude Southern oceans..
  • The October global ocean surface temperature was 0.39°C (0.70°F) above the 20th century average of 15.9°C (60.6°F), making it the 11th warmest October on record. The margin of error is +/- 0.04°C (0.07°F).
  • The United Kingdom marked its warmest October since 2006 and sixth warmest in the last 100 years, at 1.5°C (2.7°F) above the 1971–2000 average.
  • Spain had its warmest October since 1990 for the and fifth warmest over the past 50 years, at 1.8°C (3.2°F).
  • The combined global land and ocean average surface temperature for the January – October period was 0.53°C (0.95°F) above the 20th century average of 14.0°C (57.4°F), making it the 10th warmest such period on record. The margin of error is +/- 0.09°C (0.16°F).
  • The January – October worldwide land surface temperature was 0.85°C (1.53°F) above the 20th century average — the sixth warmest such period on record. The margin of error is +/- 0.19°C (0.34°F). The global ocean surface temperature for the year to date was 0.41°C (0.74°F) above the 20th century average and was the 12th warmest such period on record. The margin of error is +/- 0.04°C (0.07°F).
  • La Niña conditions strengthened during October 2011. According to NOAA's Climate Prediction Center, La Niña is expected to continue through the Northern Hemisphere winter 2011/12.
  • The average Arctic sea ice extent during October was 23.5 percent below average, ranking as the second smallest October extent since satellite records began in 1979. The extent was 2.19 million square kilometers (846,000 square miles) below average and 330,000 square kilometers (127,000 square miles) above the record low October extent set in 2007.
  • On the opposite pole, the October Antarctic monthly average extent was 1.2 percent above the 1979–2000 average, the 12th largest on record.
  • Despite a record-breaking snowstorm in the US Northeast, Northern Hemisphere snow cover extent during October was below average, and ranked as the 15th smallest October snow cover extent in the 44-year period of record. The North America and Eurasian land areas both had below-average snow cover during the month.

Please Note: The data presented in this report are preliminary. Ranks and anomalies may change as more complete data are received and processed. Effective with the October 2009 State of the Climate Report, NCDC transitioned to the new version (version 3b) of the extended reconstructed sea surface temperature (ERSST) dataset. ERSST.v3b is an improved extended SST reconstruction over version 2. For more information about the differences between ERSST.v3b and ERSST.v2 and to access the most current data, please visit NCDC's Global Surface Temperature Anomalies page.


==global-temps-errata==

Introduction

Temperature anomalies for October 2011 are shown on the dot maps below. The dot map on the left provides a spatial representation of anomalies calculated from the Global Historical Climatology Network (GHCN) dataset of land surface stations using a 1961–1990 base period. The dot map on the right is a product of a merged land surface and sea surface temperature (SST) anomaly analysis developed by Smith et al. (2008). For the merged land surface and SST analysis, temperature anomalies with respect to the 1971–2000 average 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.

October

October 2011 was much warmer than normal compared with previous Octobers. On average, land areas across the Northern Hemisphere—where the majority of the Earth's land mass is located—were the warmest on record for the month, at 1.29°C (2.32°F) above the 20th century average. The warmth was especially pronounced across Alaska, Canada, Mongolia, and most of Russia and Europe. According to the UK Met Office, the United Kingdom marked its warmest October since 2006 and eighth warmest in the last 100 years, at 2.0°C (3.6°F) above the 1971–2000 average. Norway also reported its eighth warmest October, at 1.8°C (2.6°F) above normal, with records dating back to 1900.The dot maps below show much of central and northern Russia with average temperatures more than 5°C (9°F) above average. Temperatures in the Southern Hemisphere were also above average, ranking 16th warmest on record. However, most of southern and western South America was cooler than average. According to the Argentina Meteorological Service (Servicio Meteorológico Nacional), several locations in Argentina experienced their coolest October in five decades. Globally, the average October land surface temperature was second warmest on record, at 1.10°C (1.98°F) above average.

La Niña conditions continued to strengthen in the eastern central Pacific Ocean during October, according to NOAA's Climate Prediction Center. Globally, the average October sea surface temperature was 13th warmest on record, with similar monthly average temperature anomalies in both the Northern and Southern Hemisphere oceans. While it was cooler than normal in the region of the Pacific where ENSO conditions are measured and also in the northeast Pacific, it was notably warmer than normal across the north central and northwest Pacific, the northeast Atlantic, and portions of the mid-latitude Southern oceans.

Overall, the combined global average land and ocean temperature ranked as the eighth warmest October in the 132-year period of record.

Year-to-date (January–October)

La Niña conditions have been present during all months to-date in 2011, with the exception of May, June, and July, when ENSO-neutral conditions briefly returned. These conditions impacted temperatures around the globe, making the January–October combined global land and ocean temperature the 10th warmest such period on record and the coolest since 2008, at 0.53°C (0.95°F) above average. The January-October 2011 Blended Land and Ocean Surface Temperature Anomalies in degree CelsiusJanuary–October 2011 map of temperature anomalies shows regions with anomalously warm and anomalously cool temperatures. Over land, the most anomalous warmth enveloped nearly all of central and western Russia. Few regions were cooler than normal, most notably much of northern Australia the north central and northwest United States, and southwest Canada. Overall, the global land surface temperature anomaly (0.85°C / 1.53°F) was more than twice as high as the global sea surface temperature anomaly (0.41°C / 0.74°F) for this period, ranking as 6th warmest and 12th warmest, respectively.

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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 October 2011 height and anomaly mapOctober 2011 map, respectively) are generally reflected by areas of positive and negative temperature anomalies at the surface, respectively. For other Global products, please see the Climate Monitoring Global Products page.

Images of sea surface temperature anomalies are available for each week from 2004 to present on the weekly SST page.


Temperature Rankings and Graphics

Current Month | Year-to-date

October Anomaly Rank
(out of 132 years)
Records
°C °F Year(s) °C °F
Global
Land +1.10 ± 0.11 +1.98 ± 0.20 Warmest 2nd 2005 +1.14 +2.05
Coolest 131st 1976 -0.88 -1.58
Ocean +0.39 ± 0.04 +0.70 ± 0.07 Warmest 11th 2003 +0.58 +1.04
Coolest 122nd 1909 -0.47 -0.85
Ties: 1998
Land and Ocean +0.58 ± 0.07 +1.04 ± 0.13 Warmest 8th 2003 +0.72 +1.30
Coolest 125th 1912 -0.54 -0.97
Northern Hemisphere
Land +1.29 ± 0.11 +2.32 ± 0.20 Warmest 1st 2003 +1.25 +2.25
Coolest 132nd 1912 -1.15 -2.07
Ocean +0.40 ± 0.04 +0.72 ± 0.07 Warmest 12th 2003, 2006 +0.65 +1.17
Coolest 121st 1912 -0.50 -0.90
Land and Ocean +0.73 ± 0.08 +1.31 ± 0.14 Warmest 5th 2003 +0.88 +1.58
Coolest 128th 1912 -0.74 -1.33
Southern Hemisphere
Land +0.58 ± 0.17 +1.04 ± 0.31 Warmest 16th 2006 +1.15 +2.07
Coolest 117th 1910 -0.74 -1.33
Ocean +0.39 ± 0.04 +0.70 ± 0.07 Warmest 13th 1997 +0.59 +1.06
Coolest 120th 1910 -0.46 -0.83
Land and Ocean +0.42 ± 0.06 +0.76 ± 0.11 Warmest 12th 1997 +0.62 +1.12
Coolest 121st 1910 -0.51 -0.92
Ties: 1996, 2001, 2007

January–October Anomaly Rank
(out of 132 years)
Records
°C °F Year(s) °C °F
Global
Land +0.85 ± 0.19 +1.53 ± 0.34 Warmest 6th 2007 +1.06 +1.91
Coolest 127th 1893 -0.62 -1.12
Ties: 2009
Ocean +0.41 ± 0.04 +0.74 ± 0.07 Warmest 12th 1998 +0.54 +0.97
Coolest 121st 1911 -0.47 -0.85
Land and Ocean +0.53 ± 0.09 +0.95 ± 0.16 Warmest 10th 2010 +0.66 +1.19
Coolest 123rd 1911 -0.45 -0.81
Ties: 2001
Northern Hemisphere
Land +0.96 ± 0.20 +1.73 ± 0.36 Warmest 5th 2007 +1.19 +2.14
Coolest 128th 1893 -0.67 -1.21
Ocean +0.40 ± 0.04 +0.72 ± 0.07 Warmest 12th 2005 +0.56 +1.01
Coolest 121st -0.47 -0.85 0.05
Ties: 2008
Land and Ocean +0.61 ± 0.13 +1.10 ± 0.23 Warmest 10th 2010 +0.75 +1.35
Coolest 123rd -0.47 -0.85 0.06
Southern Hemisphere
Land +0.57 ± 0.15 +1.03 ± 0.27 Warmest 12th 2005 +0.92 +1.66
Coolest 121st 1917 -0.73 -1.31
Ties: 1983, 2008
Ocean +0.43 ± 0.04 +0.77 ± 0.07 Warmest 11th 1998 +0.56 +1.01
Coolest 122nd 1911 -0.51 -0.92
Land and Ocean +0.45 ± 0.07 +0.81 ± 0.13 Warmest 12th 1998 +0.62 +1.12
Coolest 121st 1911 -0.52 -0.94

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

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Precipitation

The maps below represent anomaly values based on the GHCN dataset of land surface stations using a base period of 1961–1990. Precipitation anomalies on a month-to-month basis are often highly variable across the globe and even within regions.

There were several areas across the globe with anomalous wetness or anomalous dryness during October. With the end of the South Asian monsoon season, India and Bangladesh observed drier-than-normal conditions. It was also abnormally dry in northeastern China, eastern Australia, the central United States and much of Canada. An unusually wet monsoon season brought devastating floods to Thailand. Seasonal rains brought wetter-than-normal conditions to Algeria and Ethiopia. The remnants of Hurricane Rina affected south Florida and brought heavy precipitation in the form of snowfall to the northeast United States. Other regions that experienced above-average rainfall included eastern South America, the northwest United States, Western Australia, and Pakistan.

Rainfall across Australia was 52 percent above average, making this month the 17th wettest October in its 112-year period of record, according to Australia's Bureau of Meteorology. The wetness was due largely to well-above average rainfall in the tropical north and western half of the country. Western Australia saw average rainfall more than two times higher than normal, making this October its third wettest on record and wettest since 1975. Weak La Niña conditions were present in October, and La Niña is associated with heavier-than-average precipitation in Australia.

Additional details on extreme climate events and flooding and drought conditions can also be found on the October 2011 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 22 November 2011


early OctoberDeficient rains lead to a water shortage on the South Pacific island of Tuvalu read more October 17thGiant dust storm rolls through Lubbock, Texas read more October 1stHighest October temperature recorded for the United Kingdom read more early OctoberFloods kill 10 people in Algeria read more mid-OctoberTwo storm systems leave dozens dead across Central America. read more OctoberThailand experiences worst flooding since 1942 read more October 1stSuper Typhoon Nalgae strikes the Philippine island of Luzon read more October 12thHurricane Jova makes landfall in western Mexico near Manzanillo read more OctoberLargest algal bloom in a decade forms along the Texas Gulf Coast read more October 24thTwo people are killed amid heavy rainfall and widespread flooding in Dublin, Ireland read more October 25thStorm leaves nine people dead in Italy. read more October 26thFirst major snowfall of the season hits Colorado. read more October 14thCrack discoved in Antarctica's Pine Island Glacier read more



Drought conditions

Months of deficient rainfall associated with the climate phenomenon La Niña, in combination with well-water contamination from development and population growth and unusually high tides that have mixed salt water with ground water, led to a major water crisis on the small South Pacific island nation of Tuvalu during early October. The situation was so extreme that buckets of fresh water were rationed daily to local families. La Niña conditions in the eastern equatorial Pacific Ocean, which returned in September, continued to strengthen in October and were forecast to gradually continue to strengthen through the Northern Hemisphere winter 2011/12, according to NOAA's Climate Prediction Center. Average rainfall in Tuvalu ranges from about 8–16 inches (200–400 mm) per month.


Satellite aniomation of cold front moving across Texas south plains. Dust can be seen in light grey.
Storm System Satellite Imagery
17 October 2011
Image Credit:
National Weather Service

Wind gusts as high as 75 mph (121 km/hr), in combination with ongoing drought conditions, led to the formation of an 8,000-foot (2,400-meter) wall of dust that made its way to Lubbock, Texas on October 17th. Visibility dropped to near zero as the storm passed through. While dust storms occur occasionally in Lubbock, the timing, strength, and size of the storm was unusual, according to the National Weather Service. The high winds were due to a strong cold front moving through the region, while the drought led directly to less vegetation cover on the ground and thus provided a larger potential source of dust than in normal years. The storm damaged trees and buildings and sparked at least three wildfires in the area.

Please visit NCDC's Drought and Wildfire pages for more detailed information.

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Extreme Temperatures

On October 1st, the temperature reached 85.8°F (29.9°C) in Gravesend, Kent, setting a new monthly October maximum temperature record for the United Kingdom. The previous high temperature of 84.9°F (29.4°C) was recorded on October 1st, 1985 in March, Cambridgeshire. October 1st, 2011 was also the warmest October day ever recorded in Wales, as the temperature reached 82.3°F (28.2°C), breaking the previous record of 79.5°F (26.4°C), also set on October 1st, 1985.

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Heavy rainfall and flooding

In Algeria, days of heavy rainfall culminated in overflowing rivers and floods at the beginning of October that killed 10 people near El-Bayadh, several hundred miles south of the capital city of Algiers. Hundreds of homes were also destroyed. Heavy rain and flooding is common in Algeria during October.


Central American countries impacted by heavy rainfall during 11–20 October
Central American Countries Impact by Storms
11–20 October 2011
Image Credit:
BBC

Two separate storm systems—a tropical depression from the Pacific and another system from the Caribbean—wreaked havoc across Central America, dumping nearly five feet (1520 mm) of rain in some areas during October 11th–20th, according to officials. At least 105 deaths were reported across Honduras, Costa Rica, Guatemala, El Salvador, and Nicaragua. About one million people in total were affected by the storms, which led to major flooding and landslides.


Flooding in the historic city of Ayutthaya on 23 October
Floodwaters in Ayutthaya, Thailand
23 October 2011
Image Credit:
NASA Earth Observatory

Storms and heavy monsoon rains from late July to October contributed to the worst flooding in Thailand since 1942, affecting about nine million people. Floodwaters from the north in August slowly made their way south toward the Gulf of Thailand while heavy precipitation continued to fall. Some areas were under six feet (two meters) of water. The ancient capital of Ayutthaya, a Unesco World Heritage Site, was hit hard by the flooding in mid-October as the Chao Phraya River that surrounds the island city overflowed its banks. The death toll rose to at least 373. Twenty-seven of the country's 77 provinces remained inundated near the end of October, with four million acres (1.6 million hectares) submerged in the north, northeast, and center of Thailand. Several large industrial parks near Bangkok were impacted, idling hundreds of factories and hundreds of thousands of workers, and disrupting global shipments ranging from computer hard drives to automobiles. Damage estimates varied in different media reports, but have been as high as $6 billion U.S. dollars. Other countries in South Asia have also been affected by the heavy rainfall. An estimated 240 people were killed in Cambodia and at least 106 perished in Myanmar.


Radar imagery of rainfall across Ireland on 24 October
Ireland Rainfall Radar Imagery
24 October 2011
Image Credit: Met Eirann

Very heavy rain fell across eastern and northern Ireland on October 24th, making this the wettest October day in Dublin, Ireland since records began in 1954. A total of 3.2 inches (82.2 mm) of precipitation was recorded in South West County Dublin, with most of the rainfall (2.59 inches / 65.7 mm) occurring within a four-hour period, which is an estimated 1-in-80 year event. Average monthly rainfall for October is about 65 mm (2.6 inches). The torrential rains led to widespread flooding that killed two residents in the city.



Flooded streets with mud wall in Monterosso, Italy on 26 October
Flooded Steet, Monterosso, Italy
26 October 2011
Image Credit: Getty Images

The same storm system that affected Ireland also severely impacted parts of Italy on October 25th. Reportedly, up to 19.7 inches (500 mm) of rain fell within a 24-hour period in some locations. The popular tourist destinations of the northwestern coastal region of Liguiria and the central region of Tuscany were among the hardest hit. At least nine people were killed and six were missing due to flash flooding and landslides. Several town were isolated for days in the aftermath of the storm as roads and bridges were washed away or filled with debris.

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Tropical Cyclones

Nalgae and Nesat storm tracks and estimated rainfall totals for 26 September–2 October
Typhoons Nesat and Nalgae
24 September–2 October 2011
Image Credit:
NASA Earth Observatory

Less than a week after getting hit by Typhoon Nesat, Super Typhoon Nalgae (locally referred to as Quiel) roared ashore in the Philippines on October 1st. Similar to Nesat, the storm crossed the main island of Luzon, making landfall in Isabela province. The storm reached its maximum strength of one-minute sustained 150 mph (241 km/hr) winds—equivalent to a strong category 4 hurricane on the Saffir-Simpson hurricane wind scale. At least three people were killed before the storm weakened and moved out into the South China Sea, heading for the southern Chinese island of Hainan and then to Vietnam. The Philippines experiences about 20 storms a year on average.


Hurricane Jova estimated rainfall totals for 6–13 October
Hurricane Jova
6–13 October 2011
Image Credit:
NASA Earth Observatory

In the eastern Pacific, Hurricane Jova struck Mexico's western coast near Manzanillo on October 12th with category 2 hurricane force winds of more than 100 mph (160 km/hr). Jova weakened into a tropical depression as it moved inland. At least six people were killed. Jova was the 10th named storm and ninth hurricane of the 2011 Eastern Pacific hurricane season.

Please visit NCDC's Hurricanes & Tropical Storms page for more detailed tropical cyclone statistics.

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Severe winter weather

Just two days after a record-high daily temperature of 80°F (26.7°C) was set in Denver, Colorado on October 24th, the first major snowstorm of the season pounded the area. Several inches fell across Denver and more than a foot of snow was reported in several locations, including 19.8 inches (50.3 cm) in nearby Boulder. Tens of thousands of residents lost power as tree limbs crashed down on utility lines. Minor injuries, but no fatalities, were reported.


Snowfall in the northeastern U.S. covers a jack-o-lantern on 30 October
Snow-covered Jack-o-lantern
30 October 2011
Image Credit: AP

Mother Nature played a trick on much of the mid-Atlantic and northeastern U.S. states during October 29th–30th as an unseasonably early, record-breaking nor'easter affected residents from West Virginia to Maine, forcing the disruption of Halloween plans in addition to many other major problems. Heavy, wet snow fell on tree limbs with leaves yet to fall off, which caused the limbs to dip or break off and snap power lines, leaving more than three million residents lost power across the area and creating dangerous conditions on the ground. Connecticut's governor said that this was the largest power outage on record for the state with 800,000 residents left in the dark for up to several days. Hundreds of flights were cancelled or delayed for Philadelphia, Boston, Newark, and New York City airports and some commuter train services were suspended. Jaffrey, New Hampshire recorded the highest storm total of 31.4 inches (80 cm) with well over a foot (30 cm) of snow reported in many other locations. In Central Park, New York City, 2.9 inches (7.4 cm) of snow fell on October 29th, the first time more than in an inch (2.5 cm) of snow has been observed here during the month of October since records began in 1869. Across the region, at least 22 deaths were blamed on the storm.

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Polar Events and Sea Ice

Crack in Pine Island Glacier as spooted by NASA's Operation IceBridge on 14 October 2011
Pine Island Glacier Crack
14 October 2011
Image Credit: NASA

According to a NASA blog, the agency's Operation IceBridge saw a large crack in Antarctica's Pine Island Glacier as aircraft flew over the region on October 14th. According to NASA, Pine Island is one of the largest and fastest moving glaciers in Antacrtica. Located in West Antarctica, Pine Island Glacier is a gigantic ice stream that discharges about 100 trillion tons of ice into the Amundsen Sea every year. For several years, scientists have known that the glacier is thinning, and the rate of thinning has quadrupled over the last 18 years. According to the IceBridge project manager, the crack, which will eventually lead to calving (breaking off), is part of a natural cycle. The IceBridge team estimated that the area that could calve in the near future covers about 310 square miles (803 square kilometers). Scientists are concerned about the impact this will have on sea level rise.

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Ecosystems Impacts

The ongoing drought in Texas, which began about a year ago, has had far-reaching impacts, including to ecosystems in the Gulf of Mexico. The largest algal bloom in more than a decade—called the red tide bloom—formed along the Texas Gulf Coast and affected areas from Galveston to South Padre Island. The bloom, which depletes oxygen in the water, triggered fish kills and warnings about beach conditions, and released aerosols into the air that irritate respiratory systems. Some regions measured more than 100,000 cells per cubic millimeter of water. During years with normal rainfall, freshwater runoff into bays help keep salinity levels low enough stop these tides. The last red tide bloom occurred during 2009.

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National Snow & Ice

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.

October marks the beginning of the cold season for the United States, and snow typically begins to fall across the Northern tier of the country and the high terrain of the West. When weather conditions are averaged for the month of October 2011, most of the West had near- to above-normal precipitation. The Northeast also had above-average precipitation during the month, while the Mississippi River Valley and the central Gulf Coast had below-average precipitation. Temperatures were warmer than average across the Northern tier of the country and parts of the West, while below-normal temperatures were dominate across the Southeast. The warm temperatures across the West were associated with below-normal snow cover across the high terrain, during October.


October Snow Storm

An early October snow storm brought heavy snowfall to the Central Rockies between October 7th and 9th, but most accumulating snow fell across high elevations and had limited impacts. A late October storm between the 26th and 31st brought heavy snowfall amounts to the Front Range of the Rockies to northern Texas. The storm system then moved across the central parts of the country and into the Mid-Atlantic and Northeast where it brought snowfall from North Carolina to Maine. According to the Rutgers Global Snow Lab, a NOAA supported facility, the average snow extent across the contiguous United States for October 2011 ranked as 22nd smallest (23rd largest) in the 44-year satellite record at 38,225 square miles (99,000 square km) — 19,700 square miles (51,000 square km) below the long term average of 57,900 square miles (150,000 square km). At the beginning of the month, only the highest mountain peaks across the Pacific Northwest and Northern Rockies had snow cover, amounting to less than 0.01 percent of the contiguous United States. By the 31st, the area covered by snow increased to 6.6 percent, with snow on the ground across the Northern Rockies, the High Plains of Colorado and across most of the Northeast corridor.


Summary of Notable Snow Events:
Satellite Image of NE Snowfall
Satellite image of Northeast Snowfall 30 Oct. 2011
Source: NASA

A potent early season extra-tropical cyclone moved from the Rocky Mountains, across the U.S., into the Northeast between October 26th and 31st. The storm brought heavy snowfall across the Front Range and High Plains of Colorado. Snowfall amounts of over a foot were widespread across the region, and Ward, Colorado, received 19 inches (48.3 cm) of accumulation. The snowfall occurred two days after record high temperatures in the 70s °F and 80s °F were observed across the region. On October 28th, the storm moved eastward into the Plains, where it brought several inches of snowfall to the Texas Northern Panhandle. A new daily record of 3.1 inches (7.9 cm) of snow fell in Amarillo. The storm traversed the center of the country, where the predominate type of precipitation was rain. Between October 29th and 31st, the storm moved off the Atlantic Coast and rapidly intensified into a Nor’easter, and the northern side of the storm was cool enough to dump over a foot of snow over interior regions of the northeast. Snow was seen as far south as North Carolina. Over 30 inches of snow were reported across western Massachusetts and southern New Hamsphire. In Concord, Maine, 22.5 inches (57.2 cm) of snow accumulated between 3pm on the 29th and 7am on the 30th, setting the second greatest 24-hour snowfall on record for the city. Dozens of locations from Virginia to Maine set daily snowfall records on October 29th and 31st, as well as snowfall records for the month of October. The storm also broke the record at many locations for the most snowfall this early in the winter season. New York’s Central Park recorded 2.9 inches (7.4 cm) of snowfall during the storm — the first time since records began in 1869 that an inch or more of snowfall has been recorded during the month of October. The storm was preliminarily scored as a Category 1 (Notable) snow storm on the Northeast Snowfall Impact Scale (NESIS), which takes into account snowfall in populated areas of the Northeast. This is the first October snow storm to have significant enough impacts to be ranked on the NESIS. Significant damage was reported across the region from the storm because of the strong winds and many of the trees had not yet lost their foliage — the excess snow accumulating on branches caused them to break. The storm temperatures were also relatively warm, leading to a high water content of the snow (heavier snow). According to media reports, over 3 million people lost electricity and there were 22 storm-related fatalities.

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

Upper-level circulation pattern and anomalies averaged for October 2011
Upper-level circulation pattern and anomalies averaged for October 2011.

A vigorous weather patternweather pattern dominated the contiguous United States during October 2011. Several strong upper-level low pressure systems brought areas of rain and snow with cold temperatures, while southerly winds swept warmer-than-normal air ahead of the storm systems. Numerous wildfires affected the West at the beginning of the month, contributing to a record wildfire month for October, but weather systems later in the month dampened the wildfire activity. In spite of the active weather pattern, tornado activity was below average for the month.

A winter storm early in the month dumped snow over the high elevations of the West, with up to 6 percent of the contiguous U.S. snowcovered by October 9th, but the rest of the month saw warmer temperatures with more rain than snow, so the West ended the month with a below-normal snowpack. Near the end of the month, winter storms buried Colorado and the Northeast with blankets of snow, respectively covering up to 8.3 percent (by October 28th) and 7.4 percent (by October 30th) of the country. Heavy snow from these early-season snowstorms tied or broke over 400 daily snowfall records for the month of October and over 100 monthly October snowfall records.

October 2011 Palmer Z Index
October 2011 Palmer Z Index.

The fronts and low pressure systems brought above-normal precipitation to parts of the West, Central and Southern Plains, Florida, and parts of the Ohio Valley to Northeast, where New Hampshire and Rhode Island had the tenth wettest October on record and Massachusetts ranked eighth wettest. But large parts of the Southwest, South, and Mississippi Valley missed out on the precipitation. Iowa, Missouri, and Louisiana had the ninth driest October in the 1895-2011 record, with Alabama ranking 11th driest. Parts of the Southern Plains drought area received beneficial rainfall, but it had little effect on the year-long deficits. Drought expanded further into the Upper Mississippi Valley where little rain fell this month, with the national drought footprint rising to about 33 percent in moderate to exceptional drought.

Air flow at the surface, associated with the upper-level low pressure systems, caused numerous temperature extremes at both ends of the scale. More than 1400 daily high temperature records were tied or broken in October 2011 compared to over 1400 reports of daily high temperatures that were coldest on record. There were more than 1200 reports of record warm daily minimum temperatures and about 600 reports of record cold daily minimum temperatures. This synoptic brew of daily hot and cold weather systems cooked out into a monthly spatial pattern of below-normal temperatures in the Southeast and above-normal temperatures in the western and northern states.

Extremes in PDSI component of the U.S. Climate Extremes Index, October, 1910-2011
Extremes in PDSI component of the U.S. Climate Extremes Index, October, 1910-2011.

When averaged together, the mixture of temperature and precipitation extremes gave the U.S. the 33rd warmest and 51st driest October in the 117-year record. Averaging extremes tends to cancel them out. But when extremes are combined cumulatively, like in the U.S. Climate Extremes Index (CEI), they may tell a different story. The national CEI for October 2011 ranked near the long-term average. The large area of extremely wet and extremely dry conditions ranked seventh largest (wet) and ninth largest (dry) in the 1910-2011 CEI record, individually, but taken together they ranked second biggest.

Sea surface temperature (SST) anomalies for four La Niña/El Niño regions
Sea surface temperature (SST) anomalies for four La Niña/El Niño regions.

Cold fronts and low pressure systems moving in the storm track flow are influenced by the broadscale atmospheric circulation. Three such large-scale atmospheric circulation drivers were potentially influential during October:

Map of monthly temperature anomalies Map of monthly precipitation anomalies

The pattern of observed temperature anomalies for October 2011 and the last three months (August-October) corresponds to the AO in the Northern Plains and the PNA in the Southeast. The October 2011 and August-October 2011 precipitation patterns are a reasonable match for the La Niña and AO patterns, especially over the West and parts of the Southeast (La Niña), the Southern Plains and Upper Mississippi Valley (AO), and Great Lakes (La Niña and AO).

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.


YTD Tornado Counts
January-October Tornado Count

According to data from the Storm Prediction Center, the annual decline of tornado activity continued into October 2011, with only 23 preliminary tornado reports during the month. The 20-year average number of tornadoes during October is 61. The preliminary tornado reports during October continued to push the annual tornado count upwards, with the 2011 tornado count encroaching on the annual record of 1,817 set in 2004. During the January-October 2011 period, 1,488 tornadoes have been confirmed with 140 preliminary tornado reports still pending. This ranks the January-October 2011 period among the top three most active such periods since the modern record began in 1950.

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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.

East North Pacific Basin

Originating several hundred miles southwest of Acapulco, Mexico, Jova gradually strengthened into a tropical storm on the afternoon of October 6. Set in a favorable environment, the storm became a hurricane on October 8, and by October 10 had intensified to a strong Category 3 storm–the 5th major hurricane of the eastern Pacific season. A day prior to landfall, the storm began an eyewall replacement cycle and weakened to a minimal Category 2 hurricane. It maintained this intensity as it made landfall in the Mexican state of Jalisco just prior to midnight on October 11. With winds of 100 mph (km/h), Jova was the strongest hurricane to hit Mexico’s Pacific coast since Hurricane Jimena of 2009 (winds of 105 mph). A small storm with winds extending outward a modest 15 miles (24 km) from its center, Jova’s main threat was from torrential rains which triggered flooding and mudslides, claimed 8 lives, and caused an estimated $27.7 million (U.S. dollars) in damages. Coquimatlan, Colima, Mexico reported the highest rainfall total with 14.74 inches (374.4 mm); this challenges the state’s all-time record hurricane rainfall of 15.57 inches (395.5 mm) set in 1998 by Hurricane Javier. As the storm passed over the rugged terrain of western Mexico, it quickly dissipated, becoming post-tropical within 24 hours.

Jova
Tropical Storm Jova Satellite Image
Jova Track
Tropical Storm Jova Forecast Track


Safir Simpson Color Legend for Track Map from Unisys
Saffir-Simpson Scale Color Legend
Tropical Cyclone Summary
Tropical Cyclone Jova
Cyclogenesis Date 10/06
Cyclolysis Date 10/12
Highest Saffir-Simpson Category Cat 3
Maximum 6-hr Sustained Wind 127 mph (110 kt or 204 km/h)
Min Pressure 955 mbar
Accumulated Cyclone Energy (ACE*) Index (kt2) 14.5200 x 104
Landfall Information (date, location and sustained winds) 10/12 – Jalisco, Mexico (85 kt or 157 km /h)
Deaths 8
*The (ACE) Index calculations are based on preliminary data.

On the morning of October 6, an area of disturbed weather emerged 700 miles (1126.5 km) northwest of Tropical Depression Ten-E (Jova). Just 5 hours later, it surpassed Jova in strength, and was named Tropical Storm Irwin. Irwin strengthened to a Category 1 hurricane the following day, then downgraded on October 8; the storm fluctuated between tropical storm and tropical depression intensity the remainder of its lifespan. While initially forecast to impact the same stretch of coastline as Jova, Irwin came within 145 miles (235 km) of Manzanillo, Mexico, then drifted southwestward back into the Pacific–an unusual track for an eastern Pacific tropical cyclone, the majority of which move west-northwestward. On October 16, the storm became a remnant low while out to sea.

Irwin
Tropical Storm Irwin Satellite Image
Irwin Track
Tropical Storm Irwin Forecast Track


Safir Simpson Color Legend for Track Map from Unisys
Saffir-Simpson Scale Color Legend
Tropical Cyclone Summary
Tropical Cyclone Irwin
Cyclogenesis Date 10/06
Cyclolysis Date 10/15
Highest Saffir-Simpson Category Cat 1
Maximum 6-hr Sustained Wind 92 mph (80 kt or 148 km/h)
Min Pressure 977 mbar
Accumulated Cyclone Energy (ACE*) Index (kt2) N/A
Landfall Information (date, location and sustained winds) 7.9825 x 104
Deaths 0
*The (ACE) Index calculations are based on preliminary data.


Atlantic Basin

Near mid-October, a large low pressure system located within 100 miles (170 km) of the Nicaragua-Honduras border brought 3 to 10 inches (76.2 to 254 mm) of precipitation to locations in South Florida, Cuba, and the Yucatan Peninsula. On October 23, the system organized into a tropical depression and was named Tropical Storm Rina by that day’s close. Twenty–one hours later, Rina strengthened to the 6th hurricane of the Atlantic season. It peaked as a strong Category 2 storm, then weakened, making landfall near Cozumel, Mexico on the night of October 27 as a tropical storm. Rainfall totals included 8.2 inches (208 mm) in Cozumel and 1.89 inches (48 mm) in the popular tourist locale of Cancun. While no injuries were reported, an estimated 10,000 tourists evacuated the region. The following day, the storm degenerated to a remnant low over the Yucatan Channel. Its moisture was absorbed into the southerly flow of a rare 2011 Halloween nor’easter which affected the mid-Atlantic and Northeastern U.S.

Rina
Tropical Storm Rina Satellite Image
Rina Track
Tropical Storm Rina Forecast Track


Safir Simpson Color Legend for Track Map from Unisys
Saffir-Simpson Scale Color Legend
Tropical Cyclone Summary
Tropical Cyclone Rina
Cyclogenesis Date 10/24
Cyclolysis Date 10/28
Highest Saffir-Simpson Category Cat 2
Maximum 6-hr Sustained Wind 109 mph (95 kt or 176 km/h)
Min Pressure 966 mbar
Accumulated Cyclone Energy (ACE*) Index (kt2) 9.2075 x 104
Landfall Information (date, location and sustained winds) N/A
Deaths 0
*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 November 2011
Contents Of This Report:
Map showing Palmer Z Index

National Drought Overview

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Detailed Drought Discussion

Overview

October 2011 was near-average (33rd warmest and 51st driest, based on data back to 1895) when weather conditions are averaged across the country. But this reflected regional extremes (in both monthly temperature and precipitation, as well as weekly regional patterns of temperature anomalies [weeks 1, 2, 3, 4] and precipitation anomalies [weeks 1, 2, 3, 4]). Parts of the Southern Plains and Southeast drought areas received beneficial rainfall, but it had little effect on deficits that have accumulated over the last 12 months. Drier-than-normal weather during October, combined with dryness during the previous two months, expanded drought in the Upper Midwest and Plains areas along and west of the Mississippi River. Two-thirds of Hawaii was rated in moderate to exceptional drought at the end of October — a jump of 22 percent compared to last month, due to a dry October. Drought coverage increased in the Southeast (42 percent in moderate to exceptional drought at the end of September rising to 45 percent at the end of October), South (76 to 80 percent), Midwest (14 to 24 percent), and High Plains (17 to 23 percent) regions, but remained steady in the West region (Southwest). Nationally, the moderate-to-exceptional drought footprint increased to about 27 percent of the country, but the percentage in the worst category (D4, exceptional drought) dropped to about 7 percent.

U.S. Drought Monitor map from September 27, 2011
The U.S. Drought Monitor drought map valid November 1, 2011.

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

  • a large area of moderate (D1) to exceptional (D4) drought across the Southwest, Southern and Central Plains;
  • moderate to extreme drought in the Southeast;
  • areas of expanding moderate to severe (D2) drought in the Midwest to Northern Plains; and
  • much of Hawaii, where moderate to extreme drought persisted.

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

As seen on the October 2011 Palmer Z Index map, low precipitation led to short-term drought across the Midwest to Upper Mississippi Valley, central Gulf Coast states, and areas along the border with Mexico this month. Evapotranspiration due to above-normal temperatures is a decreasing factor as we transition to the cold season this time of year. Wet conditions are evident on the Z Index map over a large area from the eastern Ohio Valley to the Northeast, southern Florida, and parts of the Rockies into the central High Plains. Compared with the September 2011 PHDI map, the October 2011 PHDI map indicates that drought conditions intensified along the southern Gulf Coast and spread further into the Mid-Mississippi Valley; drought conditions improved in southern Florida; moist conditions decreased in the Pacific Northwest and parts of the Midwest to western Great Lakes and Upper Mississippi Valley; and moist conditions increased from the eastern Ohio Valley to Northeast. The October 2011 PHDI map also reflects the long-term nature of the drought conditions. The Z Index and PHDI maps in combination show that heavy rains brought relief to the southern Florida drought area, near normal October moisture conditions occurred over parts of the southern drought areas, and dry weather further dried out parts of the Midwest to Upper Mississippi Valley, but for the other southern drought areas and Northeast — precipitation fell where it was already wet and it was drier than normal 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

Dryness is evident across the Central Gulf Coast states during October (1 month map), the Central to Upper Mississippi Valley and adjacent Plains at 1 to 3 months, parts of the Pacific Northwest to Northern Rockies at 2 to 3 months, the Southwest and Southern Plains at 2 to 24 months, and the Southeast at 3 to 24 months. The Southwest to Southern Plains dryness is most severe at 6, 9, and 12 months. Wet conditions caused by several strong low pressure systems can be seen at 1 month; Tropical Storm Lee rains show up in the Northeast at 2 to 3 months; and the flooding spring rains in the Midwest and Northern Plains show up at 6, 9, and 12 months. In addition to the Northern Plains and Midwest to Northeast wetness, the usually wet conditions from last winter across much of the West are evident in the 12- and 24-month time scales, although dry conditions were eroding into the western wet areas. This illustrates the persistence of the dry and wet areas.


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

Agricultural and Hydrological Indices and Impacts

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

Drought conditions were reflected in numerous agricultural, hydrological, and other meteorological indicators, both observed and modeled. Across the drought areas of the Southeast, streamflows were low and many groundwater well stations were at or near record low levels for this time of year. Low streamflows also characterized the drought areas of the Southwest and Southern Plains, where soil moisture was depleted, water restrictions were implemented in many communities, and pastures, rangeland, crops, and natural vegetation were ravaged. Vegetation was stressed and soils dry in the Southeast drought areas as well, and into the Mid- to Upper-Mississippi developing drought areas. Parts of the Southwest, Southern Plains, Central Gulf Coast, and Midwest to Upper Mississippi Valley had few, if any, days with rain in October. This summary is based on the following observed and modeled indicators:

hydrological:

USGS groundwater map
USGS groundwater map.

agricultural:

VegDRI (Vegetation Drought Response Index) map
VegDRI (Vegetation Drought Response Index) map.

meteorological:

Map of maximum consecutive dry days
Map of maximum consecutive dry days.

Regional Discussion

October 2011 was another drier-than-normal month for most of the stations in the Hawaiian Islands. The prolonged dryness of the last 2 to 3 months caused the percent of the state in moderate to exceptional drought to jump to 66 percent, with virtually all of the state (99 percent) classified in the D0-D4 categories (abnormally dry to exceptional drought). The dryness at 6 months was not as severe, but significant longer-term deficits (last 12, 24, 36 months) remained, especially for the southern islands. Streamflow was below to much below normal and October SPI values were consistently drier than normal for most locations.

Most stations in central and southern Alaska were drier than normal this month, with October 2011 ranking as the fifth driest October in the 1918-2011 record. Dryness was evident at longer time scales (2, 3, 6, 12, 24, 36 months). The October 31st snow water content was below normal, but this is early in the season and the snow depth amounts this time of year are typically low. Although the last 2 months have been dry, August was much wetter, ranking the last 3 months as the 38th wettest August-October statewide, so there was no drought or abnormal dryness indicated on the November 1st USDM.

Most of Puerto Rico was drier than normal during October. The precipitation pattern at 2 months was mixed, but above-normal rainfall dominated at longer time scales (3 and 6 months, and year to date), and streamflow was near average, so the November 1st USDM map had no drought or abnormally dry areas on the island.

State precipitation ranks, August-October 2011 State precipitation ranks, November 2010-October 2011

On a statewide basis, October 2011 ranked in the top ten driest Octobers for three states along the Mississippi River (Louisiana, Missouri, and Iowa), and five other states in the Mississippi Valley and Central Gulf Coast ranked in the dry third of the historical record. For the last three months (August-October 2011), prolonged dryness in the Upper Mississippi Valley ranked Iowa and Minnesota fifth driest, while Texas ranked sixth driest and 12 other states (in the Southeast, Great Plains, and Northwest) ranked in the dry third category. The dryness in the Southern Plains and Southeast lowered the ranks at longer time scales, with five states (New Mexico, Texas, Oklahoma, Louisiana, and Georgia) in the top ten driest category, and another eight in the dry third category, for May-October. The same five states (New Mexico, Texas, Oklahoma, Louisiana, and Georgia) were in the top ten driest category for January-October, and these same five plus South Carolina were in the top ten driest category for the last 12 months (November 2010-October 2011). Record dryness occurred for Texas at several time scales and Louisiana for December 2010-October 2011, while New Mexico and Oklahoma ranked second driest for several time scales. Widespread and persistent dryness gave the Rio Grande and Texas Gulf Coast river basins the driest November-October in the 1895-2011 record.

Rio Grande River Basin Precipitation, November-October, 1895-2011 Texas Gulf Coast Basin Precipitation, November-October, 1895-2011

Percent area of the contiguous U.S. in moderate to exceptional drought, 2000-2011
Percent area of the contiguous U.S. in moderate to exceptional drought, 2000-2011

During October, moderate to exceptional drought expanded to 80 percent of the South region, 45 percent of the Southeast region, 24 percent of the Midwest region, 23 percent of the High Plains region, and 66 percent of Hawaii. But beneficial rains during the month shrank the worst drought category (D4, exceptional drought) in the South region from 54 percent last month to 42 percent this month. Exceptional drought shrank from 86 percent to 65 percent for Texas, from 66 percent to 43 percent for Oklahoma, and from 35 percent to 26 percent for New Mexico. It dropped from 11 percent last month to 9 percent this month for the contiguous United States.

On a more localized basis, record dryness has occurred for at least one climate division in the Midwest, Southern Plains, or Southeast at every time scale from September-October 2011 through the 12-month period, November 2010-October 2011. Record warm temperatures have occurred for at least one climate division during every time scale from August-October 2011 back through November 2010-October 2011, especially in the Southern Plains during the spring and summer:

Precipitation anomaly maps:
Temperature anomaly maps:
PHDI for Texas climate division 5 (Trans Pecos), January 1900-October 2011
PHDI for Texas climate division 5 (Trans Pecos), January 1900-October 2011.

The prolonged and intense drought conditions caused a rapid intensification of the PHDI, with several climate divisions reaching record dry PHDI values during the summer. Beneficial October rains backed off the PHDI values to only near-record intensity for many of these climate divisions, but the Trans Pecos division (Texas division 5) still had a record dry PHDI at the end of October. Two river basins (the Rio Grande and the Texas Gulf Coast Basin) also had record dry PHDI values for October 2011.

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.

This water year (October through the following September) began (October 2011) with a mixed precipitation pattern over the West. Parts of the Southwest, Pacific Northwest, and Intermountain Basin were drier than normal, with other parts (especially the Northern Rockies) wetter than normal. A winter storm early in the month dumped snow over the high elevations of the West, but the rest of the month saw warmer temperatures with more rain than snow, so the West ended the month with a below-normal snowpack. The previous water year (October 2010-September 2011) left the West with moist conditions in the north and dry conditions in the south, as reflected in modeled soil moisture and the PHDI, although conditions were drying out some in recent months (2, 3 months) in the Northwest. An analysis of early data by the USDA indicated that reservoir levels were, on average, below normal in New Mexico but near to above average in most other western states. According to the USDM, 19 percent of the West was experiencing moderate to exceptional drought at the end of October, about the same as September, while the Palmer Drought Index statistic was about 15 percent, a decrease of about 1 percent. When the statistics for the Arizona-New Mexico-Colorado drought area (the Southwest drought area) are aggregated, the percent area in moderate to exceptional (USDM categories) drought has fluctuated between 60 and 70 percent for the last eight months. The percent area in the exceptional and extreme to exceptional categories steadily increased from March to June then leveled off with monsoon showers in July, then decreased slightly in August, holding steady at about 32 percent in extreme to exceptional drought at the end of this 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 Southeast in October. Monthly totals were at least 150 percent of normal across the Florida Peninsula, with some locations exceeding 300 percent of normal. In contrast, October was unusually dry across most of Puerto Rico and the U.S. Virgin Islands. St. Thomas recorded just 1.95 inches (49.5 mm) of precipitation for the month, which was nearly 3.5 inches (88.9 mm) below average. The driest locations across the Southeast (less than 25 percent of normal) were found across Alabama and northwest Florida. Mean temperatures in October were between 1 and 4 degrees F (0.5 and 2.2 degrees C) below average across most of the Southeast region, except along coastal sections of North Carolina and Virginia. Monthly temperatures were generally above average across Puerto Rico and the U.S. Virgin Islands.

There were relatively few changes to the USDM in October. Extreme drought (D3) conditions continued across much of Georgia, eastern portions of Alabama, the upstate of South Carolina, and the western panhandle of Florida. There was a slight improvement from extreme (D3) to severe drought (D2) across parts of central and southern Georgia, while drought conditions were completely eliminated across most of the Florida Panhandle. Drought conditions expanded across Alabama, where precipitation deficits were the greatest.

As explained by the Southern Regional Climate Center, with the exception of central Texas and eastern Tennessee, the bulk of the Southern region experienced a very dry October. In central Texas, stations averaged between 100 and 250 percent of normal precipitation for the month. It is worth noting that these stations received between 4 to 8 inches (101.60 to 203.20 mm) of precipitation for the month. In eastern Tennessee, stations averaged between 100 to 200 percent of normal precipitation, or approximately 3 to 6 inches (76.20 to 152.4 mm) for the month. In contrast, conditions were extremely dry in Louisiana, Mississippi, eastern Texas, and southern Arkansas. Stations in southern Louisiana and southern Mississippi averaged only between 0 to 25 percent of normal, or approximately 3 to 5 inches (76.20 to 127.00 mm) less than they normally receive for the month. Louisiana averaged only 0.82 inches (20.83 mm) for the month, making it their ninth driest October on record (1895-2011). For Mississippi, it was the seventeenth driest October on record with an average precipitation total of 1.10 inches (27.94 mm). Other state average precipitation totals for the month include: Arkansas with 2.48 inches (62.99 mm) of precipitation, Oklahoma with 2.67 inches (67.82 mm) of precipitation, Tennessee with 2.39 inches (60.71 mm) of precipitation, and Texas with 2.18 inches (55.37 mm) of precipitation. Average temperatures varied spatially in the Southern region. For Mississippi, it was the twelfth coldest October on record (1895-2011), while Louisiana recorded its twentieth coldest October on record (1895-2011). In Tennessee it was the eighteenth coldest October on record (1895-2011).

Drought conditions did not change much from September to October in Mississippi, Tennessee and Arkansas. Conditions did change, however, in Texas, Oklahoma and Louisiana. In Oklahoma, much of the central portion of the state saw a one-category improvement from exceptional drought to extreme drought. This was also the case for central Texas, where rainfall was abundant. In Louisiana, the southeast parishes went from being drought-free to moderate drought. In addition, much of the western part of the state was now experiencing exceptional drought. In total for the Southern region, there was a decrease in exceptional drought from 53.77 percent areal coverage to 41.90 percent areal coverage.

The bulk of weather impacts for the Southern region continued to pertain to the longstanding Texas drought. The effects of the drought and wildfires on Texas agriculture have been devastating. Cotton has been particularly hard hit with a loss of more than half of the 7.1 million acres planted this season. With prices being extremely high, cotton crop losses alone have translated into a $1.8 billion loss to the Texas cotton industry. Precipitation during the second half of October helped to replenish livestock tanks and ponds and helped with the planting of fall crops and winter forages, but much more additional precipitation will be needed to maintain growth. Additionally, Texas corn farmers were expected to harvest only about half of the normal 200 million bushels the state normally produces each year. The devastating wildfire season has been estimated to have caused $200 million in damage to Texas agriculture alone. Overall, the $5.2 billion in estimated 2011 losses to Texas agriculture set in August have only increased since this estimate was put forth (Information provided by the Texas Office of State Climatology).

As summarized by the Midwest Regional Climate Center, October precipitation varied considerably across the Midwest. The western half of the region received below normal precipitation while the eastern half received above normal precipitation. Totals ranged from less than 25% of normal in parts of Missouri and Iowa to more than 200% of normal in parts of Ohio. October temperatures fluctuated throughout the month. Despite starting the month with a couple days of cold temperatures, the first half of the month was above normal on average. The second half of the month was below normal despite having a brief warm spell. On average, the month was near normal for much of Missouri, Illinois, Indiana, and Ohio. Kentucky had below normal temperatures, while Iowa, Minnesota, Wisconsin, and Michigan were slightly above normal for the month.

Drought conditions in October improved in eastern Illinois and western Indiana but further west there was expansion and intensification of drought. The small area of moderate drought at the beginning of the month in northern Iowa and southern Minnesota expanded and intensified to severe drought by the end of the month. By the end of October, roughly 20% of Illinois, 40% of Minnesota, 50% of Missouri, and 70% of Iowa were designated in drought.

As noted by the Northeast Regional Climate Center, after a wet August and September, the Northeast began to dry out when high pressure settled over the region around the 5th of October. A series of rain events occurred, followed by a major snowstorm during the second half of the month. The end result was above normal precipitation in the Northeast for the third month in a row. The region's average of 4.83 inches (122.7 mm) was 126 percent of normal. It was the 20th wettest October since 1895. Delaware was the only state with below normal precipitation, at 85 percent of normal. The Northeast averaged warmer than normal for the 10th consecutive month.

As explained by the High Plains Regional Climate Center, the High Plains region experienced a wide range of weather conditions this October including record warmth, record cold, severe storms, variable precipitation, and snow. Overall, temperature departures generally ranged from near normal in the south up to 8.0 degrees F (4.4 degrees C) above normal in the north. Many locations across North Dakota ranked in the top 10 warmest Octobers on record. Little precipitation fell in the eastern part of the region, along the eastern sides of North Dakota, South Dakota, Nebraska, and Kansas. Some locations in these areas were ranked in the top 10 driest Octobers on record. Although the dryness led to the development of abnormally dry and moderate drought conditions, the dry weather did help harvesting activities progress as many days were suitable for fieldwork. By the end of the month, the harvesting of most row crops was either completed or nearing completion. Extremely dry conditions were present early in the month and numerous fires were reported in Nebraska and South Dakota. These fires destroyed crops, combines, center pivots, and even homes. One fire in Stapleton, Nebraska, which is north of North Platte, burned over 25,000 acres and caused around $4 million in damages. Meanwhile, other areas of the region received over 200 percent of normal precipitation. These areas included central Nebraska, northwestern Kansas, pockets of Colorado, and southeastern and northwestern Wyoming.

As summarized by the Western Regional Climate Center, October saw a startup of the winter storm season and the 2011-2012 water year. The first such storm arrived during the early days of October, followed by another significant event about mid-month, and providing above normal precipitation for much of the West. Temperatures were near normal throughout most of the West, with areas of above normal temperatures throughout Montana, Wyoming, eastern California, Nevada, and southern Arizona. Other parts of the West had near normal precipitation. Western Oregon and southern Arizona and New Mexico were drier than normal at most stations. October 2011 was the 16th driest year on record at Eugene, Oregon airport, with a precipitation total of 1.81 in (46 mm), or 51% of the 3.54 in (90 mm) October average. Tucson, Arizona received 0.06 in (1.5 mm), only 7% of the average 0.87 in (22 mm) for that location, making it the 29th driest October on record at Tucson. The low precipitation in the Southwest allowed drought conditions and extent to persist for Arizona and New Mexico throughout October.

Upper Colorado River Basin: As reported by the Colorado Climate Center, the November 1st NIDIS (National Integrated Drought Information System) assessment for the Upper Colorado River Basin (UCRB) indicated that, in October, precipitation favored the higher elevations of the UCRB. The northern and central mountains of Colorado, the Wasatch mountains in Utah, and the San Juans in southern CO all received between 1 and 4 inches of moisture for the month, with some isolated spots in the San Juans and northeast UT receiving over 4 inches. East of the basin, the Sangre de Cristos had accumulations of around 2 inches and northeast CO also received over an inch for the month. Southeast CO and the Colorado River valley in southeast UT were somewhat drier, receiving less than half an inch in many spots. Water-year-to-date (WYTD) SNOTEL precipitation percentiles were in the near normal range throughout most of the UCRB indicated a good start to the winter snowfall season. In the San Juan basin (around the Four Corners), snowpack was near average for the beginning of the season. After a large event earlier in the month, much of the snowpack melted, but was quickly replenished by another system, keeping snowpack near average, and slightly above last year's early accumulations. As of October 30th, 97% of the USGS streamgages in the UCRB recorded normal (25th - 75th percentile) or above normal 7-day average streamflows, with 4 gages recording below-normal flows. During the last week of October, cooler-than-average temperatures dominated most of the UCRB and eastern CO. With the cooler fall conditions and continuous widespread precipitation throughout the drought-stricken areas of southeast CO, water demands eased. The VIC model showed poor soil moisture conditions where long-term dryness has prevailed for much of the year over southeast CO. Most of the UCRB had near-average soil moisture with the Wasatch range in UT and the mountains near the Colorado Headwaters showing wet soils. Parts of eastern UT and Sweetwater County, WY continued to show drying soils. All of the major reservoirs above Lake Powell in the UCRB ended the month near or above their average October volumes. Flaming Gorge and Lake Granby were well above their averages, at 111% and 112% respectively. Lake Powell ended the month at 89% of average and 71% of capacity, compared to 63% of capacity last year.

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, below-normal rainfall over most areas of the state during the month of October resulted in an increase in drought intensity and coverage in all four Hawaii counties. All of this occurred prior to the onset of wet conditions which commenced at the end of October and continued into early November. The most notable change in drought depiction since the end of September occurred on the island of Maui where leeward areas deteriorated to extreme drought, or D3 category conditions on the USDM map, from Kamaole to Kaupo. Severe drought, or D2 category conditions, also increased in coverage and encompassed the lower elevations of west Maui from Maalaea through Lahaina. The western third of Molokai worsened from moderate drought, or D1 category, to severe drought. On the Big Island, extreme drought continued along the lower elevations of the south Kohala district, the leeward north Kohala district and the southern end of the Kau district. Severe drought also continued over most of the north Kona district, the Pohakuloa region of the Hamakua district and the eastern portion of the Kau district. Moderate drought also spread to the windward slopes above 3000 feet. Localized drought conditions developed over the lower elevations of southeast Kauai with a small area of severe drought developing near Kalepa following two months of rainfall at less than 50 percent of normal. Severe drought has affected portions of the state of Hawaii continuously since June 2008.

Some drought impacts in Hawaii include the following:

  • On Kauai, ranchers in the Kalepa area of southeast Kauai have had to purchase feed for cattle due to poor pasture conditions.
  • On Oahu, the water supply in the Waimanalo reservoir continued to decrease and has dropped over 35 feet since early in the year. The State of Hawaii Department of Agriculture implemented a mandatory 10 percent cutback in irrigation water use on October 17.
  • On Molokai, the State of Hawaii Department of Agriculture has kept in place the mandatory 30 percent cutback in irrigation water consumption for the Kualapuu reservoir system.
  • On Lanai, pastures and general vegetation conditions were in a degraded state. No additional impact information has been received though rainfall totals have been very low.
  • On Maui, pasture and vegetation conditions were very poor over the leeward slopes of Haleakala especially from Kamaole to Kaupo. One rancher reported having less than three weeks of feed left and was supplementing with molasses and alfalfa. Water supply levels for upcountry Maui had been decreasing through October but the late October-early November surge in rainfall has helped increase reservoir supplies. The Maui County Department of Water Supply has maintained their call for a 5 percent reduction in water use. The request for a 10 percent reduction in water use by central and south Maui residents also remained in effect.
  • On the Big Island, drought conditions began affecting agriculture even on the normally wetter northeast slopes of the island where a rancher in upper Paauilo reported dry pastures above 3000 feet. Pastures and general vegetation from Kawaihae to north Kona were in very poor condition and brush fires continued to be a significant concern. In September the USDA Farm Service Agency reported that various areas of the island had 30 to 100 percent loss of forage for livestock. Many ranchers have already destocked cattle and water hauling operations have been ongoing for several months. Coupled with higher feed prices, the impact on ranching operations has been significant. In other areas of agriculture, yields for tangerines, oranges, and pummelos were down about an average of 50 percent.

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, October rainfall was near to below normal in Micronesia, but near to above normal at most other locations.

Pacific Island Percent of Normal* Precipitation
Station Name Nov 2010 Dec 2010 Jan 2011 Feb 2011 Mar 2011 Apr 2011 May 2011 Jun 2011 Jul 2011 Aug 2011 Sep 2011 Oct 2011 Nov 2010-Oct 2011
Chuuk 66% 85% 76% 137% 156% 109% 66% 218% 124% 147% 120% 80% 113%
Guam IAP 53% 76% 205% 166% 138% 142% 95% 96% 195% 109% 121% 128% 124%
Kapingamarangi 25% 9% 22% 2% 61% 74% 69% 247% 199% 214% 181% 111% 89%
Koror 94% 75% 163% 145% 170% 130% 180% 129% 166% 145% 269% 107% 147%
Kosrae 74% 76% 82% 67% 51% 74% 151% 114% 76% 105% 86% 104% 88%
Kwajalein 158% 37% 119% 316% 277% 49% 91% 121% 100% 135% 101% 122% 121%
Majuro 142% 95% 100% 190% 188% 28% 109% 97% 118% 106% 108% 107% 112%
Pago Pago 82% 92% 183% 110% 52% 36% 35% 132% 40% 60% 26% 126% 86%
Pohnpei 97% 75% 98% 125% 148% 47% 95% 128% 85% 120% 97% 72% 97%
Saipan 82% 43% 182% 124% 164% 209% 154% 174% 110% 120% 64% 131% 115%
Yap 98% 69% 164% 123% 171% 129% 169% 113% 157% 133% 155% 101% 131%
* 1971-2000 Normals

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

NH Snow Cover Extent

October marks the beginning of the cold season for the Northern Hemisphere and storms begin bringing snow to the higher latitudes and elevations. During October 2011, the Northern Hemisphere snow cover extent was 761,000 square km (294,000 square miles) below the long-term average of 17.9 million square km (6.9 million square miles). The monthly value ranks as the 15th smallest October snow cover extent in the 44-year period of record.

Across North America, snow cover extent for October 2011 was below average. The U.S. and Canada both had below average snow cover extent during the month. The North American snow cover extent was 194,000 square km (74,900 square miles) below the long-term average of 8.1 million square km (3.1 million square miles). This is the 18th smallest October snow extent since the satellite record began in 1967. For the continent, below-average snow cover was observed across the U.S. and Canadian Rockies, the Canadian Pacific Ranges, and eastern Hudson Bay. Above-average snow cover was observed along the U.S. northeastern coast, the eastern Canadian prairies, and along the Arctic coast. For more information on the U.S. October 2011 snow events, please visit the U.S. October Snow/Ice Summary page.

Eurasian snow cover extent was also below average for October 2011, with an aeral extent of 9.3 million square km (3.6 million square miles), 568,000 square km (219,000 square miles) below average. This was the 18th smallest October snow extent on record. Above-average snow cover was observed for eastern Russia, northern Kazakhstan, and the Tibetan Plateau, while below-average snow cover was observed over central and western Russia, and the Himalayas.

Data were provided by the Global Snow Laboratory, Rutgers University.

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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 October 2011 was 7.10 million square kilometers (2.74 million square miles). The monthly extent was 23.5 percent below the 1979-2000 average and ranked as the second smallest October Northern Hemisphere sea ice extent in the satellite record. The October 2011 Arctic sea ice extent was 333,000 square kilometers (127,000 square miles) larger than the lowest October extent on record in 2007. Northern Hemisphere sea ice extent has declined at a rate of 6.6 percent per decade. The NSIDC stated that by the end of October, ice extent remained below the 1979 to 2000 average in the Beaufort and Chukchi seas and in the Barents and Kara seas. Extent was near average in the East Greenland Sea. By the end of the month, new ice growth closed both the Northwest Passage and the Northern Sea Route. This is the 15th consecutive October and 125th consecutive month with below-average Arctic sea ice extent.

October 2011 Southern Hemisphere sea ice extent was 1.2 percent above the 1979-2000 average. This was the 12th largest (22nd smallest) October Southern Hemisphere sea ice extent on record. Southern Hemisphere October sea ice has increased at an average rate of 0.8 percent per decade.

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: Beginning in December 2010, all data are reported here with respect to the 1981–2010 base period. Prior to December 2010, radiosonde data were reported with respect to the 1961–1990 base period and satellite data were reported with respect to the 1979–1998 base period. Remote Sensing Systems continues to provide data to NCDC with respect to the 1979–1998 base period; however, NCDC readjusts the data to the 1981–2010 base period so that the satellite measurements are comparable. This change provides a more consistent comparison between the various datasets.

Note: Effective with the January 2011 report, Remote Sensing Systems (RSS) transitioned to a new version (3.3) of the RSS MSU/AMSU atmospheric temperature datasets. Information about the differences between version 3.2 and 3.3 is available.

Troposphere

Lower Troposphere

October Lower Troposphere
October Anomaly Rank
(out of 33 years)
Record Years Decadal Trend
°C °F Year °C °F °C °F
UAH +0.12 +0.22 Coolest 22nd 1985 -0.41 -0.74 +0.16 +0.30
Warmest 12th 2005 +0.35 +0.63
RSS -0.01 -0.02 Coolest 15th 1985 -0.38 -0.68 +0.14 +0.26
Warmest 19th 1998 +0.37 +0.67
Year-to-Date Lower Troposphere
January–
October
Anomaly Rank
(out of 33 years)
Record Years Decadal Trend
°C °F Year °C °F °C °F
UAH +0.16 +0.29 Coolest 25th 1985, 1984 -0.32 -0.58 +0.14 +0.25
Warmest 8th 1998 +0.49 +0.88
RSS +0.06 +0.11 Coolest 22nd 1985 -0.38 -0.68 +0.14 +0.26
Warmest 12th 1998 +0.51 +0.92

Mid-troposphere

October Mid-troposphere
October Anomaly Rank
(out of 33 years)
Record Years Decadal Trend
°C °F Year °C °F °C °F
UAH -0.06 -0.11 Coolest 10th 1985 -0.34 -0.61 +0.08 +0.14
Warmest 23rd 1998 +0.31 +0.56
RSS -0.09 -0.16 Coolest 10th 1985 -0.41 -0.74 +0.10 +0.17
Warmest 23rd 1998 +0.33 +0.59
UW-UAH +0.03 +0.05 Coolest 19th 1985 -0.39 -0.70 +0.15 +0.28
Warmest 14th 1998 +0.43 +0.77
UW-RSS -0.02 -0.04 Coolest 17th 1985 -0.44 -0.79 +0.15 +0.28
Warmest 17th 1998 +0.43 +0.77
Year-to-Date Mid-troposphere
January–
October
Anomaly Rank
(out of 33 years*)
Record Years Decadal Trend
°C °F Year °C °F °C °F
UAH +0.01 +0.02 Coolest 17th 1993, 1989, 1984 -0.24 -0.43 +0.05 +0.10
Warmest 16th 1998 +0.49 +0.88
RSS +0.01 +0.02 Coolest 17th 1985 -0.29 -0.52 +0.09 +0.16
Warmest 17th 1998 +0.50 +0.90
UW-UAH +0.09 +0.16 Coolest 24th 1984 -0.31 -0.56 +0.11 +0.20
Warmest 8th 1998 +0.59 +1.06
UW-RSS +0.08 +0.14 Coolest 23rd 1985, 1984 -0.32 -0.58 +0.14 +0.26
Warmest 11th 1998 +0.58 +1.04
RATPAC* +0.15 +0.27 Coolest 46th 1965 -0.82 -1.48 +0.15 +0.28
Warmest 9th 2010 +0.54 +0.97

*RATPAC rank is based on 54 years of data

Stratosphere

October Stratosphere
October Anomaly Rank
(out of 33 years)
Record Years Decadal Trend
°C °F Year °C °F °C °F
UAH -0.45 -0.81 Coolest 7th 2000 -0.65 -1.17 -0.45 -0.82
Warmest 27th 1991 +1.59 +2.86
RSS -0.38 -0.68 Coolest 6th 2000 -0.55 -0.99 -0.35 -0.62
Warmest 28th 1991 +1.58 +2.84
Year-to-Date Stratosphere
January–
October
Anomaly Rank
(out of 33 years)
Record Years Decadal Trend
°C °F Year °C °F °C °F
UAH -0.41 -0.74 Coolest 3rd 2008, 1996 -0.47 -0.85 -0.37 -0.67
Warmest 30th 1983 +1.01 +1.82
RSS -0.35 -0.63 Coolest 3rd 1996 -0.40 -0.72 -0.29 -0.53
Warmest 31st 1992 +0.98 +1.76

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: 6 October 2011


Overview

During October 2011, approximately 507,724 acres (205,470 hectares) burned across the country, the most on record for the month. Most of the wildfire activity during the month occurred across the interior West, during the first two weeks of the month. The previous record for October acreage burned occured in 2007, when 469,496 acres (190,000 hectares) were burned. During the January-October period, 8.23 million acres (3.33 million hectares) burned across the U.S. — the 4th most in the 12-year period of record. The most acres burned during the January-October period occurred in 2006 when 9.40 million acres (3.80 million hectares) burned nationwide.

1-Month Wildfire Statistics*
October Totals Rank
(out of 12 years)
Record 2000-2010
Average
Value Year
Acres Burned 507,724 Most on Record 507,724 2011 211,434
12ᵗʰ Least
Number of Fires 3,399 8ᵗʰ Most 7,651 2000 4,271
5ᵗʰ Least
Acres Burned per Fire 149.4 2ⁿᵈ Most 158.9 2004 62.6
11ᵗʰ Least
Year-to-Date Wildfire Statistics*
January–October Totals Rank
(out of 12 years)
Record 2000-2010
Average
Value Year
Acres Burned 8,229,183 4ᵗʰ Most 9,400,909 2006 6,242,529
9ᵗʰ Least
Number of Fires 63,821 8ᵗʰ Most 87,809 2000 70,251
5ᵗʰ Least
Acres Burned per Fire 128.9 2ⁿᵈ Most 145.9 2005 88.9
11ᵗʰ Least

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

Discussion

During October, wetter-than-normal conditions were present across the Northeast, and the interior western states. Drier-than-normal conditions dominated the month along the Mississippi Valley. The remainder of the country — the Southeast, Southern Plains, and Southwest — received near-normal precipitation amounts for the month. Two-thirds of the country had October temperatures which were near to above normal, while the Southeast was the only region of the country cooler than normal. See the U.S. Temperature and Precipitation discussion for more information. According to the U.S. Drought Monitor, the overall size of the drought footprint (D1-D4) expanded from 29.1 percent of the contiguous U.S. at the end of September to 32.6 percent of the contiguous U.S. at the end beginning of November. Meanwhile, the percent area of the contiguous U.S. experiencing Exceptional Drought (D4) shrank. Drought conditions remained generally unchanged across the Southeast, with the exception of a few locations that received isolated heavy rainfall during October. Beneficial precipitation across the Southern Plains improved drought conditions by one to two categories across northern Texas, eastern Oklahoma, and southeastern Kansas. Drought conditions also improved slightly across portions of southern Arizona. To the north, across the Central and Northern Plains, drought conditions worsened by one to two categories. Severe Drought (D2) conditions became more widespread during October across Iowa, Minnesota, and Illinois. A large area of the Northern Rockies was classified as being abnormally dry at the end of October.

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).

At the beginning of October, there were 26 large wildfires burning across the country. There were two large wildfires burning across the Pacific Northwest in interior Oregon (1) and Washington (1) where high fire danger and extremely low 10-hour fuel moistures were reported. Thirteen large wildfires were active across the Great Basin in Nevada (11) and Utah (2). Dry conditions dominated across the region during the end of September, increasing the fire danger and Keetch-Byram Drought Index (KBDI), drying fuels of all sizes (10-hour, 100-hour, and 100-hour fuel moistures). Seven large wildfires were burning across Idaho (3), Montana (3), and Wyoming (1), where high fire danger and low 10-hour and 100-hour fuel moistures were reported. Two large fires burned in Southern California (1) and Arizona (1). Across the region, extremely low 10-hour fuel moistures were reported. One large wildfire was active in northern Texas, where on-going drought has caused fuels of all sizes to remain dry (10-hour, 100-hour, and 1,000-hour fuel moistures) and led to high KBDI values across the state. The Pagami Creek Fire in northern Minnesota continued to burn where low 10-hour fuel moistures were reported.

At mid-October, the large wildfire activity across the country subsided significantly, and only three large wildfires were active. Two large wildfires were burning across Oklahoma (1) and Arkansas (1). On-going drought across the region led to high fire danger. Reported 10-hour fuel moistures were also moderately low, with extremely high KBDI values. The Pagami Creek Fire in northern Minnesota continued to burn during mid-October. Cooler temperatures helped to increased fuel moistures and lower fire danger and KBDI values across the region, which aided fire fighters to fully contain the fire.

By October 31st, only two large wildfires were burning across the country. One large fire was active in eastern Oklahoma, where ongoing drought has continued to create ideal wildfire conditions. The prolonged dry conditions caused high KBDI values across the region, while dry conditions on the shorter term dried out small fuels and lowered 10-hour fuel moistures. The other large fire was burning in central Idaho. Relatively wet conditions the second half of the month caused low fire danger across the region, but dry conditions over the longer term caused moderately low 100-hour and 1,000-hour fuel moistures.


All Fire Related Maps


Citing This Report

NOAA National Climatic Data Center, State of the Climate for October 2011, published online November 2011, retrieved on December 19, 2014 from http://www.ncdc.noaa.gov/sotc/2011/10.