Drought - October 2012
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Contents Of This Report:
National Drought Overview
Detailed Drought Discussion
October 2012 marked a departure from the warmth of the last 16 months, averaging cooler than normal (44th coolest October on record, based on data back to 1895) with near-average precipitation (52nd wettest October), when weather conditions are averaged across the country. Like the last couple months, cool fronts swept across the country (weeks 1, 2, 3, 4, 5), but this time the monthly temperature pattern had below-normal temperatures covering more of the country — stretching from Montana to Alabama. High pressure (High, or upper-level ridge), with its descending air ("subsidence"), dominated the Southwest, resulting in a monthly pattern of anomalous warmth there with below-normal precipitation which stretched into the Central and Southern Plains. The Northeast was dominated by warmer-than-normal temperatures and, for most of the month, dry weather. The storm track kept above-normal precipitation mainly across the northern states and Midwest, with the remnants of Hurricane Sandy combining with a cold front to bring wet conditions to the Northeast at the end of the month (weeks 1, 2, 3, 4, 5). The wet weather improved drought conditions in the Midwest and virtually eliminated them in the Northeast, but dry weather helped intense drought keep its grip across much of the Plains, West, and Hawaii. Nationally, the moderate-to-exceptional (D1-D4) drought footprint decreased to about 50 percent of the country, compared to last month, while the percentage in the abnormally dry to exceptional drought category decreased to about 66 percent. About 16 percent of the country was in the worst drought categories (D3-D4, extreme to exceptional drought), a bit less than last month. The Palmer Drought Index, whose data go back 113 years, is relied upon for drought comparisons before 2000. The October 2012 Palmer value of 49 percent in moderate to extreme drought is a decrease of about 3 percent compared to last month, and the percent area in severe to extreme drought decreased to about 34 percent.
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 stretching from the Central Rockies, across the Northern to Southern Plains, into the Upper Midwest and Mid-Mississippi Valley;
- a persistent area of moderate to exceptional drought in the Southeast;
- a lingering area of moderate drought in the Mid-Atlantic;
- an area of moderate to extreme (D3) drought across much of the West; 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.
Used together, the Palmer Z Index and PHDI maps show that some long-term drought areas (north and Midwest) received short-term relief, while for other areas (Southwest, Southeast, and Southern Plains), short-term dry conditions exacerbated long-term drought. Precipitation from frontal systems along the Pacific Northwest to Northern Plains nibbled at the northern edge of the nation's drought area, while rain from Midwest fronts and the Sandy system cut away at the drought area from the east (October PHDI compared to September PHDI). Above-normal precipitation from these systems, as well as the massive area of below-normal temperatures (which reduced evapotranspiration), contributed to a reduced area of short-term drought (as seen on the Palmer Z Index map). But long-term drought intensified (October PHDI compared to September PHDI) over the Southwest and Southern Plains where the Palmer Z Index map showed short-term drought due to warmer- and drier-than-normal October conditions.
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.
The 1-month SPI shows the main area of dryness extending from the Southwest and Central Rockies to the Southern and Central Plains, with another dry area centered in the Southeast. At 2 to 3 months, the epicenter of dryness shifts to the Central Plains, Upper Midwest, Intermountain Basin, and up and down the Rockies. The 6- to 9-month SPI maps have dryness expanded into the Ohio Valley and further in the West. At 12 months, dryness is generally oriented from the Southwest to Central and Northern Plains, with some dry areas in the Upper Midwest. Dryness at 24 months is mostly concentrated in the central and southern portions of the Plains and Rockies. The Southeast is dry at virtually all time scales, but the dryness is most severe at 24 months. For the Central Plains and Rockies, the dryness is most severe at 3 to 12 months.
On the other (wet) side of the coin, wet conditions are evident at 1 month from the Pacific Northwest to extreme Northern Plains and from 1 to 6 months and at 24 months for the Northeast. The Midwest shows recent wetness (1-3 months), intermediate dryness (6-12 months), and longer-term wet conditions (24 months). Parts of the Deep South (mainly Gulf coast) are wet on the 3- to 12-month SPI maps, while the Pacific Northwest is generally wet from 6 to 12 months.
Agricultural and Hydrological Indices and Impacts
Drought conditions were reflected in numerous agricultural, hydrological, and other meteorological indicators, both observed and modeled.
Based on end-of-October (October 31st) USDA reports, 54 percent of the nation's pasture and rangeland was rated in poor to very poor condition. Several states, from California to the Central Plains, had 80 percent or more of their pasture and rangeland rated poor to very poor, with virtually all of it so rated in Nebraska and California. Winter wheat emergence was hampered by drought in several central and northwestern states, with 65 percent of the winter wheat in drought. Overall, 15 percent of the winter wheat was rated in poor to very poor condition, although that number was much higher in South Dakota (61 percent) and Nebraska (49 percent). Topsoil moisture has recovered where precipitation has fallen (October 28 compared to September 30), but conditions are still very dry where it hasn't. More than 90 percent of the topsoil was rated short or very short of moisture in New Mexico and Nebraska, and over 70 percent so rated in Wyoming, Colorado, Oklahoma, and even Georgia.
- USDA (U.S. Department of Agriculture) observed soil moisture conditions, departures and percentiles, and comparison to 5-year average and 10-year average;
- the Palmer Crop Moisture Index (CMI), which normally improves as the seasons transition to fall, but which depicted lingering agricultural drought in some southern states (weeks 1, 2, 3, 4, 5);
- NOAA Climate Prediction Center (CPC) modeled soil moisture anomalies and percentiles for the end of the month, and soil moisture anomaly change compared to previous month;
- CPC's Leaky Bucket model soil moisture percentiles;
- NLDAS (North American Land Data Assimilation System) modeled soil moisture percentiles for the top soil layer and total soil layer;
- VIC (University of Washington Variable Infiltration Capacity macroscale hydrologic model) modeled soil moisture percentiles, and soil moisture percentile change compared to previous month;
- USDA observed pasture and rangeland conditions;
- Vegetation Drought Response Index (VegDRI);
- the NOAA/NESDIS satellite-based Vegetation Health Index (VHI);
- USGS observed streamflow;
- VIC 1-, 2-, 3-, and 6-month runoff percentiles;
- NLDAS modeled streamflow anomalies and percentiles;
- NLDAS model runoff anomalies and percentiles;
- USGS groundwater observations (real-time network, climate response network, total active network);
- USDA reservoir storage as percent of capacity;
- total precipitation (plotted by the USGS, NOAA National Weather Service [NWS], and NOAA High Plains Regional Climate Center [HPRCC]);
- percent of normal precipitation and precipitation percentiles (NWS, HPRCC station observations, Leaky Bucket model);
- NCDC statewide precipitation ranks;
- USGS number of days with precipitation and maximum number of consecutive dry days;
- temperature departures from normal (HPRCC) and temperature percentiles (CPC, Leaky Bucket);
- NCDC statewide temperature ranks; and
- number of record warm daily low temperatures, record daily high temperatures, record daily low temperatures, and record cool daily high temperatures, set during the month (from NCDC's daily records analysis).
Hawaii: October 2012 was a very dry month for the Hawaiian Islands. The pattern of below-normal rainfall was evident at most time periods (last 2, 3, 6, 12, 24, and 36 months), especially for the southern islands, and streamflow was below normal for most of the islands. Moderate to extreme drought affected 52 percent of the state, a little more than last month.
Alaska: It was drier than normal in the southeast and along the southern coast, but wetter than normal at most interior and northern stations, during October 2012. A pattern of dryness extends from the southeast panhandle to interior southeast stations at 2 and 3 months, with some hint of that pattern continuing at the longer time scales (6, 12, 24, and 36 months). An area of abnormal dryness covered the northern areas on the USDM map.
Puerto Rico: The south central and southeast coastal areas and central region of the island were drier than normal this month. Above-normal rainfall over other parts of the island helped bring the monthly streamflow back to near normal levels. But the October rainfall was not enough to make up for earlier precipitation deficits. A dry band stretched across the southern and central portions of Puerto Rico at 2, 3, and 6 months, with the southeast dry for the year to date. The October 30th USDM map was free of any drought or abnormally dry areas.
CONUS State Ranks:
Only about five percent of the U.S. was very dry (the driest ten percent of the historical record) during October 2012. This stands in marked contrast to the previous five months when up to a third of the country was very dry. On a statewide basis, October 2012 ranked in the driest third of the historical record for Octobers for nine states — mostly in the Southwest and Southern to Central Plains — with Texas having the ninth driest October in the 1895-2012 record.
The spatial pattern of dryness at the three month time scale was centered in the Central to Northern Plains. Nebraska and Wyoming had the driest August-October in the historical record, followed by Minnesota (second driest) and South Dakota (fourth driest). In total, 14 states, mostly in the Rockies and Great Plains, ranked in the driest third of the historical record. A similar spatial pattern of dryness is evident at the six month time scale, except it extended farther east into the Ohio Valley. Again, Nebraska and Wyoming had the driest May-October on record, with six other states ranking in the top ten driest (Kansas (second driest), Oklahoma (fourth driest), South Dakota (fourth driest), Iowa (fifth driest), Missouri (fifth driest), and Colorado (sixth driest)). In fact, Nebraska had the driest July-October and June-October as well, and Wyoming also had the driest June-October. Eleven additional states ranked in the driest third of the historical record.
For the year-to-date, the 3- and 6-month spatial pattern is evident — plus dryness in the Southeast shows up. Nebraska and Wyoming ranked driest for January-October 2012, and four other states ranked in the top ten driest category [Colorado (third driest), New Mexico (sixth driest), Iowa (seventh driest), and Kansas (tenth driest)]. Sixteen other states ranked in the driest third of the historical record, including Georgia (17th driest) and South Carolina (31st driest). At the 12-month time scale, dryness dominated from the West to the Midwest, with pockets of dryness in the Southeast and coastal Mid-Atlantic. November 2011-October 2012 ranked in the top ten driest category for five states, with 14 other states ranking in the driest third of the historical record. Again, Nebraska and Wyoming had the driest November-October on record, followed by Colorado at third driest, Utah at sixth driest, and South Dakota at seventh driest. The dryness in the Central Plains and Central Rockies was so severe and persistent this year that both Nebraska and Wyoming had the driest period on record in 2012 for all periods from the last six months (May-October) through the last twelve months (November-October). Not only was 2012 record-breaking, but Wyoming shows evidence of a long-term drying trend over the last hundred years.
The combination of well-above normal temperatures and well-below normal precipitation brought the PDSI to very low levels in the core drought area this summer, although it did not reach record low levels on a statewide basis. In 2012, Nebraska's PDSI fell to the lowest values since the 1950s, while Wyoming's rivaled the record low set in 2002. Colorado's PDSI suggested that the 2012 drought episode was the third worst episode after 2002 and 1934. New Mexico's was a continuation of last year which, together, rival the record 1950s drought. In South Dakota, the recent dryness lowered the 2012 PDSI to the most severe level since the 1930s, but this bucked a trend toward wet conditions for the last couple decades.
As noted earlier, 15 percent of the winter wheat crop was rated in poor to very poor condition. Although October precipitation for the Winter Wheat agricultural belt was near average regionally (with October 2012 ranking 51st driest), the preceding months have been quite dry (April-October 2012 ranked as the fourth driest such period in the 1895-2012 record), thus drying out soils going into the winter wheat growing season (which begins in October). Conditions were even drier in the smaller Primary Hard Red Winter Wheat belt, with October 2012 ranking 20th driest and April-October 2012 ranking second driest (behind 1956). With April-October 2011 ranking eighth driest, the last two years have severely depleted the soil moisture in this area. The aggregate PDSI for the Primary Hard Red Winter Wheat area reached the lowest value since the 1950s, while the PDSI for the broader Winter Wheat area was far less extreme since this larger area encompassed counties that have seen wetter conditions recently. For comparison, the PDSI for the Spring Wheat belt (map) dropped from record wet only a few months ago to the driest since 1988, and similarly for the Primary Corn and Soybean belt.
According to the U.S. Army Corps of Engineers, monthly lake-wide mean levels on Lakes Michigan, Huron, and Superior were near record lows during the month of October. Drought has affected parts of the Great Lakes during 2012; however, it was not as severe as in the Midwest and Great Plains. For example, the last twelve months (November 2011-October 2012) for the U.S. climate divisions surrounding Lake Superior was slightly drier than normal, which would not account for such low lake levels. But November 2011-October 2012 was the warmest such period in the 1895-2012 record. Persistent warmth for most of the last two decades, with the accompanying above-normal evaporation, could be a factor in the low lake levels. The entire Great Lakes Basin had the warmest November-October on record this year and the last couple of decades have been persistently warmer than normal, but precipitation basin-wide has been on the wet side in recent decades.
The PDSI for the Great Lakes Basin was only slightly negative this summer. For other basins (such as the Rio Grande and Upper Mississippi basins), the PDSI was nowhere near a record. But for others (such as the Missouri and Upper Colorado basins), the 2012 drought approached previous records. And for the much bigger Mississippi River and its tributaries north of Memphis, Tennessee, into which the Missouri and Ohio rivers flow, drought was beginning to show up in 2012.
Beneficial precipitation fell in the northern parts of the West this month, relieving moisture stress that had developed during the previous two months. But for much of the rest of the West, October 2012 was drier than normal, as seen in data from both the low elevation stations and high elevation (SNOTEL) stations. The Southwest was especially afflicted with short-term drought this month due to the combination of below-normal precipitation and above-normal temperatures (which increased evapotranspiration). Some of the October precipitation fell as snow, with snow water equivalent percentile and percent of normal values relatively high, especially in the north, but this is due largely to snow depth normals being low this early in the season. Reservoir storage was below average, statewide, in most of the western states, but near to slightly above average in Montana and Washington where beneficial precipitation has fallen. According to the USDM, 76 percent of the West was experiencing moderate to exceptional drought at the end of October, a one percent increase compared to September. The Palmer Drought Index percent area statistic was about 63 percent, a ten percent jump compared to last month.
A more detailed drought discussion, provided by the NOAA Regional Climate Centers and others, can be found below.
West — Upper Colorado River Basin — Pacific Islands
As described by the High Plains Regional Climate Center, October 2012 was cooler than normal for the majority of the region. Ample precipitation was confined to North Dakota and small pockets elsewhere in the High Plains region this month. Much needed precipitation fell in areas of northern North Dakota, where precipitation totals were over 150 percent of normal. While this precipitation was not record-breaking, it did help alleviate drought conditions there. A large portion of the region continued to have dry conditions this month. Central Nebraska, central South Dakota, southern Kansas, southern and northwestern Colorado, and south-central Wyoming all had precipitation totals which were less than 25 percent of normal. The dry weather helped with the harvesting of row crops in many areas across the region. The corn harvest was ahead of average in Kansas, Nebraska, North Dakota, and South Dakota. The soybean harvest was also well ahead of average in Nebraska, North Dakota, and South Dakota. On the downside, dryness continued to affect pasturelands as most of the region continued to have pasture conditions in the very poor to poor classifications. Dry and windy conditions also took their toll on winter wheat progress. For instance, the lack of precipitation limited winter wheat emergence in parts of South Dakota and some winter wheat had to be reseeded in Nebraska due to wind damage. Although mid-October showers did help with winter wheat emergence, according to the National Agricultural Statistics Service (NASS), more precipitation is needed for improved emergence.
Slight changes in drought conditions in the High Plains region occurred over the past month, according to the USDM. Some areas experienced improvements and others had degradation which balanced out to little change over the past month. Nebraska was still the hardest hit state, with nearly 78 percent of the state in exceptional drought conditions (D4) which was up a few percent from the end of last month. South Dakota had the most degradation with a significant increase in D4 that went from 7 to 33 percent coverage over the past month. The most significant improvements occurred in the Red River Valley of North Dakota where precipitation in the middle of the month helped downgrade all extreme drought conditions (D3) to severe drought conditions (D2) in the state. Other areas which had improvements included north central Colorado, eastern Kansas, far southeastern Nebraska, and central North Dakota.
Even with the growing season coming to a close, the ongoing drought has continued to have impacts across the region. The combination of an intense low pressure system to the east and high pressure over the Rockies created very strong northwest winds over the High Plains region October 17-18. The strongest wind speeds occurred on the 18th when winds were sustained at 35-45 mph (56-72 km/h) for much of the day. Gusts to 50-60 mph (80-97 km/h) were quite common and some peak wind gusts topping 70 mph (113 km/h) were reported as well. The combination of these winds and dry conditions from the ongoing drought caused a large dust storm to form. The dust storm reduced visibilities and many roads were forced to close, including portions of I-80 in western Nebraska and eastern Wyoming, I-70 in eastern Colorado, and I-35 in Kansas and Oklahoma. Unfortunately, wildfires also started during this time period and spread rapidly. According to NASS, in Nebraska, buildings, machinery, and even crops were lost in these fires. Impacts ranging from overturned semi-trucks to downed power lines to roof and tree damage were reported all across the wind swept region.
As explained by the Southern Regional Climate Center, October was a slightly cooler than normal month for much of the Southern region. With the exception of Tennessee and northern Mississippi, October was much drier than normal month in the Southern region. A large portion of the region, including Oklahoma, Texas, Louisiana and southern Mississippi, received approximately half the normal amount of precipitation or less. Conditions were extremely dry throughout much of northwestern Texas and central Oklahoma, with many stations receiving only 5 to 25 percent of normal precipitation. Texas averaged only 0.83 inch (21.08 mm) of precipitation, making it their ninth driest October on record (1895-2012). The state of Oklahoma averaged 1.28 inches (32.51 mm), which is their twentieth driest October on record (1895-2012). Louisiana experienced its thirty-sixth driest October on record (1895-2012) with a state average precipitation of 1.83 inches (46.48 mm). Conversely, conditions were wetter than normal in Tennessee. The state averaged 4.03 inches (102.40 mm), making it their twenty-fourth wettest October (1895-2012). Other state average precipitation values include Mississippi, which averaged 3.56 inches (90.42 mm), and Arkansas, which averaged 3.33 inches (84.58 mm). Despite widespread dryness in October over much of the Southern region, drought conditions have not changed significantly over the past month. Slight improvements occurred in western Tennessee and in northern Mississippi. There was also a one category improvement in northern Arkansas, which improved from exceptional drought to severe and extreme drought. Elsewhere, conditions remained relatively unchanged.
As summarized by the Midwest Regional Climate Center, October temperatures in the Midwest were below normal for the second straight month. Statewide October temperatures ranked among the coolest 25 percent on record (1895-2012) in all Midwest states except Michigan and Ohio. Though both September and October have been below normal, the 2012 year-to-date temperatures still rank as the warmest on record dating back to 1895 (Iowa, Minnesota, Missouri, and Wisconsin) or the second warmest (Illinois, Indiana, Kentucky, Michigan, and Ohio) for every state in the region.
October precipitation varied widely with amounts less than a half inch (13 mm) in western parts of Minnesota and Missouri and totals exceeding 10 inches (254 mm) along the southern shore of Lake Erie. Totals were more than twice normal for October in most of Ohio, far eastern Kentucky, the thumb of Michigan, extreme northeast Minnesota, and a swath from southeast Minnesota to Upper Michigan. Snowfall in the Midwest was limited to the upper Midwest with totals of 3 to 5 inches (8 to 13 cm) in parts of northern Minnesota and Upper Michigan. Snow also fell in parts of Ohio and Kentucky as the remnants of Hurricane Sandy brought precipitation from the northeast seaboard all the way to the eastern reaches of the Midwest at the end of the month.
Drought conditions improved slightly during October. Areas in drought dropped from about 70 percent to 56 percent while areas in extreme drought fell from 16 percent to 11 percent of the Midwest. Cooler temperatures have helped to lower evapotranspiration in the region allowing for more of the precipitation to help recharge soil moisture. Harvest continued ahead of normal across the region. All nine states were ahead of normal for corn harvest while soybean harvest was either near normal or slightly ahead of normal. According to the US Army Corps of Engineers, monthly lake wide mean levels on Lake Michigan-Huron and Lake Superior were near record lows during the month of October. By the end of October, the mean lake wide level of Lake Michigan-Huron was 576.6 feet (175.748 m), which is within 1.5 inches (38 mm) of the record October low set back in 1964 and 1965 and only about 7 inches (178 mm) above the all-time record low lake level of 576 feet (175.565 m) in March 1964. By the end of October, Lake Superior was 15 inches (381 mm) below the long-term October average.
As noted by the Southeast Regional Climate Center, for the third straight month, mean temperatures were near normal across much of the Southeast region. The warmest weather occurred during the first week and towards the end of the month in advance of Hurricane Sandy, with temperatures exceeding 80 degrees F (26.7 degrees C) as far north as northern Virginia. The coldest weather of the month occurred following the passage of a cold front on the 8th and in the wake of Hurricane Sandy over the final four days of the month. A month after tying its warmest September on record, San Juan, PR recorded its fourth warmest October in a record extending back to 1898.
Precipitation in October was below average across most of the Southeast. The driest locations were found across central and southern parts of Alabama, Georgia, and South Carolina, where monthly totals were less than 25 percent of normal, while the wettest locations were found across eastern sections of North Carolina and Virginia, where monthly totals exceeded 200 percent of normal in places. Precipitation in October was variable across Puerto Rico, with above normal precipitation along the northern half of the island and below normal precipitation along the southern half. Precipitation was generally above normal across the U.S. Virgin Islands, with a large portion tied to the passage of Hurricane Rafael on the 15th of the month.
There were relatively few changes to the USDM across the Southeast in October. Abnormally dry conditions (D0) expanded across southeastern Georgia, central South Carolina, and south-central North Carolina. There was a slight contraction of moderate (D2) to exceptional (D4) drought across central Georgia, while Hurricane Sandy helped eliminate drought conditions across eastern and northern sections of Virginia. By the end of the month, approximately 40 percent of the Southeast was classified in drought. The overall dry pattern in October aided in the harvesting of row crops and fall vegetables as well as the planting of winter crops. Pastures were also reported to be in good condition due to the cooler temperatures, though newly planted pastures, particularly fescue and cool season forage, could benefit from some additional rainfall. The continued dry pattern across central Georgia forced some farmers to ship in water for their livestock to offset dropping farm pond levels. Livestock and crop conditions also declined across much of South Carolina due to the lack of rainfall. High winds from Sandy contributed to some cotton damage across eastern North Carolina and delayed the harvesting of several row crops. However, the rain from Sandy provided some much needed moisture for newly planted winter wheat. Several vegetable and tobacco growers in North Carolina reported above average yields for the year, while growers in Virginia reported that peanut and soybean yields have been above average.
As explained by the Northeast Regional Climate Center, for the fourth month in a row, the Northeast was warmer than normal. While October started off dry, Hurricane/Superstorm Sandy brought record rainfall to parts of the Northeast. With a monthly total of 5.49 inches (139.45 mm), October was 143 percent of normal. Delaware received 8.89 inches (225.81 mm) of rain making it the wettest October since 1895. Maryland had its third wettest October with 4.21 inches (106.93 mm) of rain. Sandy also brought snow to parts of the Northeast. In fact it was the snowiest October on record (since 1948) for Charlestown, WV, with 10.1 inches (256.54 mm). Despite receiving rain from Sandy, Connecticut remained slightly drier than normal at 89 percent. While drought conditions improved across most of the Northeast, upstate New York was still experiencing abnormal dryness (D0) according to the USDM for October 30, 2012.
As summarized by the Western Regional Climate Center, storms began marching across the Pacific Northwest mid-month, providing the first relief from a summer dominated by below normal precipitation and developing drought. Dry conditions persisted throughout the Southwest with the exception of southern Nevada, where a slow moving low-pressure system generated heavy precipitation and thunderstorms. After receiving no measurable precipitation for 84 days (July 21-Oct 12), Wenatchee, Washington recorded 1.56 in (39.6 mm) this month, 354% of normal and Wenatchee's 3rd wettest October on record. Missoula, Montana logged 1.82 in (46.2 mm) total precipitation and 4 in (10.2 cm) snow, making for the 6th wettest and 7th snowiest October in a record that began in 1893. Despite high precipitation totals this month, 60 percent of Montana remained in moderate to extreme drought. Las Vegas, Nevada saw its 9th wettest October in a record beginning in 1888 with a total of 0.73 in (18.5 mm). In just 3 months, August 1-October 31, 2012, Las Vegas received 4.19 in (106.4 mm) of precipitation, equal to the location's 30-year normal for annual precipitation. In contrast, the first 6 months of 2012 saw only 0.25 in (6.35 mm) in Las Vegas, the 6th driest January-June period on record. The same storm system that brought precipitation to the Las Vegas area also provided rainfall to Colorado's Front Range, helping to alleviate the persistent drought in this region. A cold front passed through the Front Range late in the month, bringing over 5 in (12.7 cm) of snowfall to Denver, bringing the city's total to 1.22 in (31.0 mm) of precipitation for October, 119 percent of normal. Wyoming also received some drought relief this month from the aforementioned storm systems. Normal to slightly above normal precipitation fell in the western and southeastern portions of the state, though at month's end, 97.8 percent of Wyoming remained at some level of drought. In the Southwest, Albuquerque, New Mexico recorded only trace precipitation this month, tying the 2nd driest October since official records began in 1933.
In addition to dry conditions, above normal temperatures dominated the Southwest. Phoenix, Arizona recorded its 8th warmest October at 78.8 F (26.0 C), and Albuquerque, New Mexico noted its 10th warmest at 60.8 F (16 C). Records at Phoenix date back to 1895 and at Albuquerque to 1892. On October 6th, Ely, in northeastern Nevada, saw its second latest autumn freeze in an 89-year record, behind October 13, 1963. On the heels of its warmest August and September on record, Reno, Nevada posted an average October temperature of 58 F (14.4 C), the 5th warmest in a record beginning in 1888.
Much further north, most of interior and southeast Alaska saw near or below normal temperatures this month. In contrast, the North Slope recorded average monthly temperatures 8-10 F (4-5 C) above normal. Barrow posted an October average of 27.5 F (-2.5 C), 10.3 F (5.7 C) above normal and the warmest since records began in 1949. This warmth is likely associated with the smallest measured summer minimum of polar ice extent, well below the former 2007 record. Out in the Pacific, Lihue, Hawaii set an all-time October high temperature record of 91 F (32.8 C) on October 9th. Lihue also recorded its driest October in a record that began in 1950, receiving only 0.39 in (9.9 mm) of rainfall, 9 percent of normal. Hilo, Hawaii also had a dry October at a total of 2.91 in (73.9 mm), its 3rd driest on record. All reporting stations in Hawaii received 75 percent or less of their normal October rainfall, further exacerbating the persistent drought conditions on the lee sides of the Islands.
Upper Colorado River Basin: As reported by the Colorado Climate Center, the November 6th NIDIS (National Integrated Drought Information System) assessment for the Upper Colorado River Basin (UCRB) indicated that, for the month of October, most of the UCRB received below average precipitation. Southwest Colorado saw between 10 percent and 50 percent of average precipitation for the month. Some isolated areas in the northern CO mountains received near average precipitation. Northern Utah and western Wyoming received near to above average precipitation for the month (with some areas seeing over 200 percent of average moisture). East of the UCRB, northeast CO received near average precipitation for October while southeast CO and the San Luis Valley received below average precipitation. About half of the SNOTEL sites around the basin have started accumulating snowpack since the beginning of the water year. Very little to no snow has begun accumulating in the southern portion of the basin. Many of the northern sites have accumulated snow in the near normal range, while a few sites in central CO are showing below normal snowpack for this time of year.
As of November 4th, about 26 percent of the USGS streamgages in the UCRB recorded normal (25th - 75th percentile) to above normal 7-day average streamflows. About 35 percent of the gages in the basin are recording much below normal or low (i.e. lowest on record) streamflows, and only one gage recorded above normal flows. Much below normal flows are found scattered throughout the basin. It is important to note that with baseflows dominating during this time of year, small changes in flows can lead to large percentile changes. The VIC soil moisture model shows extremely dry soils through most of WY, with soil dryness below the 20th percentile in northeast UT and northwest CO. Deteriorating soil moisture conditions are showing up over southwest CO. Dry soils also show up in southeast CO with near normal soil moisture in north-central CO and in the San Luis Valley in southern CO. For the month of October, all the major reservoirs in the UCRB saw a decrease in storage volumes, which is normal for this time of year. Lake Granby, Navajo, Dillon, and McPhee reservoirs saw larger decreases than normal while Lake Powell and Flaming Gorge saw smaller decreases than what is normal for this time of 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, instead of a seasonal increase in rainfall, October brought record low precipitation totals at several locations across the state. Most of the records broken were on Kauai and Oahu which resulted in a degradation of existing drought conditions. On Kauai...existing severe drought...or D2 category conditions in the USDM map...worsened to extreme drought...or the D3 category...in the southeastern portion of the island. For Oahu...moderate drought...or D1 conditions...worsened to severe drought levels on the leeward areas of the Waianae range. The rest of the state remains largely unchanged in terms of drought coverage. Extreme drought is entrenched over the southwest slopes of Lanai...western Molokai and southwest Maui from Kihei to Makena. Big Island extreme drought coverage includes most of the south Kohala district...the Pohakuloa region of the Hamakua district...the north-facing slopes of Hualalai in the north Kona district and the lower elevations of southwest Kau. Severe drought conditions in Maui county cover central and northeastern Lanai...the lower leeward slopes of the west Maui mountains...and the western slopes of Haleakala from Haiku to Kaupo. On the Big Island...the main area of severe drought is in the Humuula Saddle.
Some drought impacts impacts in Hawaii include the following:
KAUAI. EARLIER REPORTS INDICATED POOR PASTURE CONDITIONS IN THE AREA FROM KALAHEO TO HANAPEPE. OTHER AREAS WITH POOR PASTURE CONDITIONS INCLUDE THE REGION FROM KOLOA TO MAHAULEPU...AND FROM KEALIA TO KALEPA. THE WATER LEVEL IN THE ALEXANDER RESERVOIR IN SOUTH KAUAI HAS DROPPED SO LOW THAT IRRIGATION WATER SERVICE HAS BEEN SUSPENDED. CATTLE HAVE BEEN REMOVED FROM THE MAHAULEPU AREA DUE TO POOR PASTURE CONDITIONS. OAHU. PASTURES AND GENERAL VEGETATION REMAIN IN POOR CONDITION OVER THE LEEWARD WAIANAE RANGE. WEST OAHU RANCHERS HAVE DESTOCKED PASTURES DUE TO POOR GRAZING CONDITIONS. DESPITE THE RECORD DRY CONDITIONS...THE WATER SUPPLY IN THE WAIMANALO RESERVOIR REMAINS ABOVE PRE-DROUGHT LEVELS. A VOLUNTARY 10 PERCENT REDUCTION IN WATER USE REMAINS IN PLACE AS A PRECAUTION. MOLOKAI. NO SIGNIFICANT CHANGES SINCE THE OCTOBER 4 UPDATE. PASTURES AND GENERAL VEGETATION CONDITIONS REMAIN VERY POOR WEST OF KAUNAKAKAI. THE WATER LEVEL IN THE KUALAPUU RESERVOIR REMAINS VERY LOW. THUS...THE STATE OF HAWAII DEPARTMENT OF AGRICULTURE HAS CONTINUED A MANDATORY 30 PERCENT REDUCTION IN IRRIGATION WATER CONSUMPTION. LANAI. NO SIGNIFICANT CHANGES SINCE THE OCTOBER 4 UPDATE. AN EARLIER REPORT FROM LANAI INDICATED THAT THE MIDDLE AND LOWER ELEVATIONS OF THE ISLAND...ESPECIALLY ALONG THE NORTH-...EAST- AND SOUTH-FACING SLOPES...REMAIN VERY DRY AND THAT PLANTS AND ANIMALS IN THESE AREAS HAVE BEEN STRUGGLING TO SURVIVE. EVEN DROUGHT-RESISTANT PLANTS AND TREES SUCH AS KIAWE WERE STRUGGLING UNDER THE DRY CONDITIONS. MOUFLON SHEEP...AXIS DEER AND GAME BIRD POPULATIONS HAVE BEEN REDUCED. MAUI. A LOW WATER SUPPLY HAS REDUCED PRODUCTION AT THE OLINDA WATER TREATMENT FACILITY IN UPCOUNTRY MAUI. PASTURES AND GENERAL VEGETATION CONDITIONS REMAIN VERY POOR IN SOUTHWEST MAUI...ESPECIALLY FROM KAONOULU TO KAMAOLE. PASTURES IN THIS AREA AND NEAR KAUPO WERE DESTOCKED SEVERAL MONTHS AGO DUE TO LACK OF SUFFICIENT FORAGE. THE MAUI COUNTY DEPARTMENT OF WATER SUPPLY HAS CONTINUED THE ONGOING CALL FOR A 5 PERCENT REDUCTION IN WATER USE FOR UPCOUNTRY RESIDENTS. THE REQUEST FOR A 10 PERCENT REDUCTION IN WATER USE BY CENTRAL AND SOUTH MAUI ALSO REMAINS IN EFFECT. BIG ISLAND. NO SIGNIFICANT CHANGES SINCE THE OCTOBER 4 UPDATE. THE RECENT BELOW AVERAGE RAINFALL HAS SO FAR NOT PRODUCED SIGNIFICANT IMPACTS OVER THE WINDWARD SECTIONS OF THE ISLAND THOUGH THIS WILL CHANGE IF RAINFALL FAILS TO INCREASE SOON. EARLIER REPORTS FROM THE KAU...NORTH KONA...SOUTH KONA AND SOUTH KOHALA DISTRICTS INDICATED SIGNIFICANT DROUGHT IMPACTS TO THE RANCHING, ORNAMENTAL PLANT, FRUIT ORCHARD, AND BEE INDUSTRIES.
On other Pacific Islands (maps — Micronesia, Marshall Islands, basinwide), October was drier than normal for Guam, Koror, Kwajalein, Lukonor, and Pohnpei, and much drier than normal for Majuro and Pago Pago. October rainfall amounts at Majuro and Pago Pago were well below six inches. Total rainfall for the last 12 months (November 2011-October 2012) was near to above normal for all stations except Majuro.
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.):
|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.|
|Contiguous United States|
- Palmer Drought Indices
- Standardized Precipitation Index
- long-term (36 to 60 month) percent of normal precipitation maps
- airport station percent of normal precipitation maps
- statewide precipitation rank maps
- Cooperative station percent of normal precipitation maps
- percent of average maps for the SNOTEL stations in the western mountains provided by the Western Regional Climate Center
- satellite-based observations of vegetative health
- National Weather Service model calculations of soil moisture, runoff, and evaporation
- National Weather Service model calculations of soil moisture using the Leaky Bucket Model
- Midwest Regional Climate Center model calculations of soil moisture
- topsoil moisture conditions observed by the USDA and mapped by the Climate Prediction Center
- pasture and range land conditions observed by the USDA and mapped by the Climate Prediction Center
- streamflow maps maintained by the USGS
Contacts & Questions