Drought - November 2010
Contents Of This Report:
National Drought Overview
Detailed Drought Discussion
November 2010 was near the long-term average (50th driest and 46th warmest, based on data back to 1895) when weather conditions are averaged across the country. But considerable variability occurred throughout the month (weeks 1, 2, 3, 4, 5) and on a regional basis. Beneficial precipitation fell across much of the Ohio Valley and Gulf Coast drought (D1-D3) and abnormally dry (D0) areas. Parts of the northern Rockies and Great Basin were also wetter than normal. But the month was persistently drier than normal across much of the Southwest, southern Plains, and mid-Atlantic to southern Atlantic coast. Abnormally dry and drought conditions expanded from Virginia to Florida and across parts of the southern Plains. Drought conditions changed very little across Hawaii.
As Northern Hemisphere autumn transitions into winter during this time of year, the angle of the sun above the horizon decreases, resulting in less solar heating of the northern latitudes. Temperatures cool, the atmospheric circulation intensifies, and strong extra-tropical cyclonic storms with associated cold fronts develop in the westerly flow. This is what happened in November as a very active weather pattern brought a series of winter storms to the Lower 48 States. Several strong low pressure systems, or extra-tropical cyclones, developed in the West or central Plains, bringing beneficial snow to the mountains and snow cover to the northern tier states. About 12 percent of the country was snow covered by the 10th of the month, with the snow coverage increasing to a third of the country with snowstorms after the 21st. A few systems developed in the South. As the storm systems moved eastward, cold air was pulled in behind them (weeks 1, 2, 3, 4, 5). Near the end of the month, moisture drawn northward along the associated cold fronts brought locally heavy rains to the Ohio Valley and parts of the South, alleviating drought conditions in some areas.
Cold fronts and low pressure systems moving in the storm track flow are influenced by the broadscale atmospheric circulation. Two such large-scale atmospheric circulation patterns were dominant during November. The first was the La Niña, which is the phenomenon created by cooler-than-average sea surface temperatures in the eastern tropical Pacific Ocean. La Niña is typically associated with wet conditions in the northern tier states and Ohio Valley this time of year, and warm and dry conditions in the southern tier states. The second atmospheric circulation index was the Arctic Oscillation (AO), which was strongly negative during the last half of November. A negative AO is typically associated with dry conditions in the Southeast and colder-than-normal temperatures east of the Rockies at this time of year (October-December).
In response to these two atmospheric phenomenon, precipitation was above normal across the northern Rockies and Ohio Valley, with Montana having the seventh wettest November on record and Indiana the 16th wettest. November precipitation was drier than normal in the Southwest, southern Plains, and parts of the Southeast, with North Carolina ranking 16th driest and New Mexico and South Carolina both 18th driest. The opposing temperature influences of these two atmospheric patterns contributed to a national temperature rank for the month near the middle of the historical distribution, with the first half of the month generally warmer than normal (weeks 1, 2, 3) and the second half of the month (when the AO turned strongly negative) colder than normal (weeks 4, 5). The circulation patterns funneled moisture and above-normal temperatures into Alaska.
By the end of the month, the core drought areas in the U.S. included:
- much of Hawaii, where moderate (D1) to exceptional (D4) drought was entrenched;
- the southern Plains to Southeast, where moderate (D1) to extreme (D3) drought expanded;
- the central High Plains, where moderate to severe drought expanded;
- the Ohio Valley, where moderate (D1) to extreme (D3) drought contracted; and
- the central Appalachians, Arrowhead of Minnesota, and parts of the West, where moderate drought lingered.
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. As seen on the Palmer Z Index map, low precipitation resulted in dry conditions for November 2010 over the Eastern Seaboard, southern Plains, and parts of the Southwest and Great Lakes. Wet conditions are evident on the Z Index map across the northern Plains and northern Rockies, parts of the Great Basin and Ohio to Lower Mississippi valleys, and a few areas in the Northeast. Compared with the October 2010 PHDI map, the November 2010 PHDI map indicates that drought conditions improved a little from the Ohio Valley to Lower Mississippi Valley, and deteriorated slightly in the central Appalachians, but otherwise little change occurred. The November 2010 PHDI map also reflects the long-term nature of the drought conditions. The Z Index and PHDI maps in combination show that the dryness in the Southeast to mid-Atlantic coast is both a short-term and long-term phenomenon, and that the dryness in the Plains is a short-term phenomenon.
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 one month to 24 months. Dryness is evident across the southern Plains at 1- to 3-month time scales, and in the Southwest for the last 3 months to 9 months. The central Plains to central Rockies have dry conditions at 2 to 3 months (Plains) and 2 to 6 months (Rockies), but they were not as dry in November. The Ohio Valley was wet in November but negative deficits still show up at 3 months. The coastal mid-Atlantic areas have been dry for the last 2 months but wet at longer time scales. Wet conditions dominated the Lower Mississippi Valley and middle Gulf Coast in November, but dry conditions are evident at 3 to 12 months. Florida and adjoining parts of the Southeast were near normal for November, but very dry conditions prevail on the maps for 2 to 9 months. Various parts of the West have wet conditions on the maps for the last 1 to 12 months. The precipitation pattern for the northern Plains to Midwest is mixed at 1 to 2 months, but very wet from 3 to 24 months.
Abnormal dryness and drought were evident in several indicators. There were hardly any days with rain from Arizona to west Texas, across parts of the central and northern Plains, and from Florida to the coastal Mid-Atlantic. This resulted in long runs of consecutive dry days in some of these areas. It is also reflected in low total precipitation amounts and below-normal precipitation. As temperatures cool during late fall and early winter, vegetation goes dormant at the end of the growing season across much of the country. But soil moisture, as monitored by several models (NOAA Climate Prediction Center [CPC] anomalies and percentiles, Leaky Bucket, NLDAS [North American Land Data Assimilation System] top soil layer and total soil layer), was still drier than average across much of the country from the southern Great Lakes to the Lower Mississippi Valley, across most of the Gulf Coast, across parts of the central and southern Rockies and Plains, and parts of Hawaii and Alaska. Satellite monitoring of vegetation health (Vegetation Drought Response Index [VegDRI], Vegetation Health Index [VHI]) indicated stress on vegetation in parts of the Southwest, southern Plains, Ohio Valley, Florida, and Hawaii.
Well monitoring stations (real-time network, climate response network, total active network) in the drought-stressed areas continued to show low groundwater levels. Streamflow (observed and modeled [CPC anomalies and percentiles) was below average for the month across much of the Southeast and Gulf Coast and parts of the Great Lakes, Southwest, and Hawaii.
Above-normal precipitation fell across most of Alaska during November 2010. Consequently, the snow water content and snow density of the SNOTEL Network stations and Alaskan river basins improved compared to last month. The November 30th USDM map had a third of the state in the abnormally dry category to reflect long-term deficits which still remained at several stations at longer time scales (3, 6, 12, 24, 36 months).
Much of Puerto Rico was drier than normal during November. Eastern parts of the island were drier than normal at the 60- and 90-day time scales, but wet conditions more than made up for the recent dryness in other areas and at longer time scales (180 days and year to date). Streamflow for Puerto Rico was near normal and the island remained drought free on the November 30th USDM map.
A few stations in Hawaii had above-normal rainfall during November, but most reported below-normal amounts. Long-term deficits (last 3, 6, 12, 24, 36 months) continued to climb. About half of the state was classified in moderate (D1) to exceptional (D4) drought at the end of November, based on the USDM.
On a statewide basis, November 2010 was drier than normal for many states along the Atlantic coast and in the Southwest and southern Plains, but the longer time scales had even drier conditions. September-November 2010 was the second driest fall for Florida and below normal for several other states in the Southeast, Ohio Valley, and Rockies. Several states, from the Lower Mississippi Valley to the mid-Atlantic coast, had a drier than normal June-November, including Florida which, again, ranked second driest. The same region was drier than normal for the year to date, with Louisiana in the top ten category with a rank of seventh driest.
Record wetness and dryness occurred at several time scales for some of the climate divisions in the contiguous U.S. (November, September-November, June-November, February-November, January-November, December 2009-November 2010). Some climate divisions having record dry conditions include:
- Texas Trans Pecos (division 5): October-November
- Texas Edwards Plateau (division 6): October-November
- North Central Florida (division 3): September-November
- South Central Florida (division 4): September-November
- South Central Arkansas (division 8): March-November
- West Central Louisiana (division 4): January-November and December 2009-November 2010
Percent area of the Western U.S. in moderate to extreme drought, January 1900-November 2010, based on the Palmer Drought Index.
November 2010 was wetter than normal across much of the northern Rockies and northern High Plains to Great Basin and the Central Valley of California, but drier than normal for parts of the Pacific Northwest and much of the Southwest. This pattern — especially the dry Southwest — is typical of a La Niña. Precipitation for the water year to date (October-November 2010) was above normal for much of the West at the lower elevation stations. At the high elevation (SNOTEL network) stations, precipitation for the water year to date was above normal from the central Rockies to Sierra Nevada, near-to-below normal across much of the Pacific Northwest, and well below normal for most of the Southwest. A similar pattern was evident in the mountain snowpack and snow water equivalent (stations' percentile and percent of normal, basins' percent of normal). An analysis of early data by the USDA indicated that reservoir levels were generally mixed, with levels near to above normal in the northern Rockies states and Arizona, but near to below normal in the other western states. According to the USDM, 6 percent of the West was experiencing moderate to severe drought at the end of November, about the same compared to October, while the Palmer Drought Index statistic was about 4 percent.
A more detailed drought discussion, provided by the NOAA Regional Climate Centers and others, can be found below.
As noted by the Southeast Regional Climate Center, there was a marked gradient in monthly precipitation totals across the Southeast region in November. Precipitation was between 100 and 150 percent of normal across the western part of the region, including Alabama, the western Panhandle of Florida, northern Georgia, northwestern South Carolina, western North Carolina, the western half of Virginia, and a small portion of southwest Florida. In contrast, much of the eastern half of the region remained exceptionally dry in November (25 to 50 percent of normal). The largest precipitation deficits (less than 25 percent of normal) were found in southeastern Virginia, eastern portions of the Carolinas and Georgia, and across portions of northern and southeastern Florida. Charleston, South Carolina received only 0.3 inch (7.6 mm) of precipitation for the month, making it the third driest November in a record extending back to 1938. The heaviest precipitation occurred on the last day of the month in conjunction with a large low pressure system, the center of which tracked across the Great Lakes. Asheville, North Carolina recorded 4.1 inches (104.1 mm) of rain on the 30th, which broke the all-time 24-hour precipitation total for November in a record extending back to 1902. The greatest observed 24-hour rainfall total from this event was 8.4 inches (213.4 mm) at Rosman, North Carolina, located in the southern Appalachian Mountains. Monthly precipitation totals were near normal across much of Puerto Rico. A strong feed of tropical moisture connected with the circulation of Hurricane Tomas resulted in over 4 inches (101.6 mm) of rainfall across the southern half of the island on the 6th of the month. A cold spell that occurred early in the month resulted in trace amounts of snowfall across northern sections of Alabama, Georgia, and South Carolina, 1 to 2 inches (25.4 to 50.8 mm) in the mountains of Virginia, and as much as 5 inches (127 mm) in the mountains of North Carolina.
The lack of precipitation across the eastern half of the region resulted in a re-emergence of abnormally dry conditions (D0) across the eastern Carolinas and Virginia and an expansion of moderate drought (D1) and severe drought (D2) conditions across much of Georgia and central Florida. By the end of November, approximately 87 percent of the region displayed D0 or greater conditions. A small area of extreme drought (D3) was observed in northeast Florida, while southwest Alabama saw a slight amelioration from D3 to D2 conditions by the end of the month. The continued dry pattern helped many farmers in the region complete their fall harvest, but also contributed to cabbage and potato crop damage across parts of Florida. In late November, the U.S. Department of Agriculture announced that all counties in Georgia and many others in Alabama and South Carolina would be eligible for disaster relief due to crop losses resulting in part from the unusually hot and dry weather over the past several months.
As explained by the Southern Regional Climate Center, November average daily temperatures were consistently near normal throughout the Southern region. Aside from some small pockets in Texas and eastern Oklahoma, temperatures did not deviate much beyond 3 degrees F (1.67 degrees C) of expected monthly normals. Generally speaking, much of the Southern region experienced only a slightly warmer than normal month. November precipitation totals, on the other hand, were quite variable over the Southern region. With the exception of northwestern Oklahoma and northwestern Texas, the western half of the Southern region experienced another dry month, while the south central and eastern half of the region experienced near normal to wet conditions. The driest part of the region included much of southern and western Texas, in particular, the southwest, where dozens of stations did not receive any measurable precipitation. This included numerous stations in the Trans Pecos, Edwards Plateau and Lower Valley climate divisions. Conditions were also quite dry in eastern Oklahoma and in western Arkansas. Precipitation totals varied from 25 to 50 percent of normal in central Oklahoma to between 50 and 70 percent of normal in eastern Oklahoma and western Arkansas. Elsewhere in the region, precipitation was generally within 30 percent of normal for the month, with slightly drier than normal conditions in southwestern Louisiana, southern Mississippi and central Tennessee. Conversely, precipitation was near normal throughout most of Mississippi, Tennessee and eastern Arkansas. The wettest portion of the region was in western Oklahoma and northern Texas, where precipitation totals ranged from 150 to 300 percent of normal. This equated to approximately 1 to 2 inches (25.4 to 50.8 mm) above normal conditions.
Drought conditions in the Southern region during November changed for the better in some regions, while other regions took a turn for the worse. In Mississippi, near normal November precipitation has resulted in the removal of severe and extreme drought in the western and central portions of the state. A small area of severe drought remained in the southern portion of the state. In Tennessee, Arkansas and Oklahoma, conditions did not change much over the past month. A small area of moderate drought remained in central Oklahoma. In Arkansas, there was some improvement in the southern counties, which last month had extreme drought, but this month had a one category improvement to severe drought conditions. A large part of central and eastern Arkansas, as well as western Tennessee, was still in severe drought conditions. In central Tennessee, moderate drought conditions persisted over the month. In Texas, drier than normal weather resulted in a one category deterioration (to severe drought conditions) in the southwest portion of the state, with a small area of extreme drought. Severe drought also developed in the east central counties of Texas. In Louisiana, drought conditions did not change much over the past month, with much of the state still under the influence of severe and extreme drought.
The autumn dryness and anticipation of a historically dry 2010-2011 winter has fueled fears that the upcoming Texas wildfire season could be one of the worst in years. As of December 1, 71 Texas counties had a ban on outdoor burning and many more counties were expected to join this list. Several wildfires were reported in West Texas toward the end of November, but the fire activity was limited so far. Much of the credit for a lack of fires despite the high fire danger should be given to local governments and media, who have effectively disseminated information on the prevention of wildfires. Because of the short term nature of the drought, its impact on Texas water suppliers has been minimal with a few municipalities enacting preliminary water restrictions. The dry weather had a minimal impact on the harvesting of cotton, and actually helped to dry fields that saw abundant precipitation during the growing months. However, the dry weather has had a negative impact on the growth of winter pastures and the planting of winter wheat has been difficult throughout the state. Much of the rain that did fall throughout Central and South Texas during November did so on Election Day, which lowered the voter turnout at many precincts. (Information provided by the Texas State Climate Office).
As summarized by the Midwest Regional Climate Center, November precipitation was variable across the region. Precipitation was above normal from southeastern Missouri through Ohio, and 150 percent of normal from southern Indiana to southwestern Ohio. Most of this precipitation came during the last nine days of the month, when storms dropped from six to eight inches (15 to 20 cm) of rain in southern in Indiana. The heavy rain resulted in a significant improvement in the Severe to Extreme Drought in the Ohio Valley. However, normal to above normal precipitation will be needed in the coming months to further eradicate the dry conditions. Precipitation was also near to above normal in a narrow band from southwestern Iowa to northeastern Minnesota. In southwestern Minnesota and from northern Missouri into northern Lower Michigan precipitation was about 50 percent of normal.
The fall (September, October, November) temperature departures in the Midwest were near to just slightly above normal across the region. Warm, dry weather particularly in September and October aided an early completion to harvest across most of the region. The northwestern half of the region was consistently wetter than the southeastern half during September and October, while drought worsened in the Ohio Valley. Heavy rain in late November helped reduce the precipitation deficit in the southern Midwest and Ohio Valley, mitigating the drought. For the season, precipitation was near to above normal west of the Mississippi River, and much above normal across Minnesota, the northern half of Wisconsin, and the Michigan Upper Peninsula. Precipitation across the remainder of the region was 75 percent to 90 percent of normal.
As noted by the Northeast Regional Climate Center, most of the Northeast ended up on the dry side in November, with Maine the one exception. The region averaged 3.20 inches (81.3 mm) of precipitation, most of which fell as rain. This was 86 percent of the normal November total. Maine's average precipitation total was 127 percent of normal; departures for the 11 other states in the region ranged from 56 percent of normal in New Jersey to 87 percent of normal in Massachusetts. The typical lake-effect areas of Pennsylvania and New York and the higher elevations in the region saw up to 10 inches (254 mm) of snowfall this month. Precipitation totals for the fall of 2010 averaged 12.12 inches (307.8 mm) or 109 percent of normal. Despite below normal precipitation in most of the Northeast, the USDM published November 30, 2010 indicated a slight improvement in the drought conditions. Portions of the eastern panhandle of West Virginia and the western panhandle of Maryland that were in severe drought (D2) a month ago improved to moderate drought (D1) at the end of November. Moderate drought conditions (D1) were still present in eastern West Virginia, while parts of western Pennsylvania and coastal New Jersey were abnormally dry.
The Northeast averaged 0.6 degrees F (0.3 degrees C) above normal during November with an average temperature of 39.8 degrees F (4.3 degrees C). This was the 11th consecutive month with warmer than normal temperatures, but the first month since February 2010 that at least one state in the region had a temperature average that was below normal. Maryland was that state, with an average that was 0.4 degrees F (0.2 degrees C) below normal. The remaining 11 states saw temperature departures ranging from 0.3 degrees F (0.2 degrees C) above normal in Massachusetts and West Virginia to 1.5 degrees F (0.8 degrees C) warmer than normal in Maine. Autumn 2010 (September-November) averaged 50.9 degrees F (10.5 degrees C), which was 1.4 degrees F (0.8 degrees C) above normal. This was 0.6 degrees F (0.3 degrees C) warmer than the autumn of 2009.
As explained by the High Plains Regional Climate Center, November was drier than normal for most of the region with average temperatures generally near normal across the region. Many locations across Colorado, western Kansas, central Nebraska, and eastern South Dakota received less than 25 percent of normal precipitation. In south-central Colorado, according to the USDM, ongoing dryness led to the development of severe drought conditions. Lamar, Colorado, located in southeastern Colorado on the Arkansas River, received no precipitation this month, which tied for the driest November on record (period of record 1893-2010). Also, by receiving only 0.53 inch (13 mm) of precipitation the past three months, Lamar recorded its 5th driest fall (September, October, and November) on record. The driest fall on record occurred in 1934 when no precipitation fell. There were exceptions to the dryness in northwestern and southeastern Wyoming and a swath extending from south-central Kansas through southeastern Nebraska, where precipitation was 150 percent of normal or more. In Kansas, many locations ranked in the top 10 wettest Novembers on record. This month's wet spot was Ashland, Kansas, which is located in the south-central portion of the state near the Oklahoma border. With 3.40 inches (86 mm) of precipitation, Ashland recorded its 7th wettest November on record (period of record 1900-2010). Of this precipitation, 2.36 inches (60 mm) fell on November 12 and set a new daily precipitation record. The previous record for that date was set in 1997 with 1.90 inches (48 mm) of precipitation. Snowfall in northwestern Colorado was a welcome sight as it helped alleviate abnormally dry conditions. Steamboat Springs, Colorado set its 8th snowiest November on record when it received 38.3 inches (97 cm) of snow this month (period of record 1893-2010). However, this was not nearly enough to beat the record 57.0 inches (145 cm) of snow that fell in November 1983.
The USDM showed both improvement and deterioration over the past month. Snowfall helped alleviate the moderate drought (D1) conditions in northern Wyoming and some of the abnormally dry conditions (D0) in western Colorado and northern and eastern Wyoming. However, D0 stretched into southeastern Kansas from Oklahoma and D1 spread from east-central Colorado to the east and into western Kansas. In addition, due to an ongoing lack of precipitation, severe drought conditions (D2) developed in southeast Colorado.
On a state-by-state basis, November 2010 was marked by a series of strong snowstorms that brought significant precipitation to many high-elevation locations across Wyoming. Based on reports from high-elevation NRCS-SNOTEL sites, most drainages in Wyoming were at or above historical average snowpack for this time of year. In contrast, many low-elevation sites experienced precipitation deficits for the month. In North Dakota, November's percent of normal precipitation ranged from roughly 25 percent to 300 percent of normal. Warm, dry weather stretched from the 1th through the 9th of November across the state. Light snow fell across some areas during the next ten days. A major storm system from the 21st through the 26th brought snowfall across North Dakota with blowing snow and some areas receiving freezing drizzle. The storm system caused hazardous travel for many on the Thanksgiving holiday. Following the 26th was a quiet two days but another statewide snowstorm on the 29th and 30th caused snow and blowing snow with wind gusts of 40 mph.
As summarized by the Western Regional Climate Center, precipitation was near normal for most of the West Coast, above normal for the northern Intermountain West and Great Basin, and well below normal for the Southwest. In Montana, Great Falls and Billings each recorded their 3rd wettest and 2nd snowiest November on record. Ely had their snowiest November on record and 3rd wettest dating back 72 years. No rain fell at all in parts of New Mexico and Arizona. Fairbanks measured their 3rd wettest November on record because of a very unusual rain event late in the month. Thanks to record setting cold the final 10 days of November, monthly mean temperatures were near or below normal for almost the entire region. The first week of the month saw record setting high temperatures in many locations.
Rain and Freezing Rain in Alaska: On November 22nd, an exceptionally unusual winter freezing rain event occurred throughout the state causing numerous problems. Beginning on the morning of the 22nd, much of the precipitation fell as either freezing rain or rain that froze on deeply frozen snow-packed roadways. This nearly brought Fairbanks to a halt and closed schools and state and federal offices for most of the week. Numerous flight delays and some cancellations occurred at both Anchorage and Fairbanks airports. Of note was the two-fold combination, consisting of both the unusual nature of the event itself at individual locations, and also the vast spatial extent, stretching at times from the Gulf of Alaska coast to the far northern reaches of the state.
Upper Colorado River Basin: As reported by the Colorado Climate Center, the early December NIDIS (National Integrated Drought Information System) assessment for the Upper Colorado River Basin (UCRB) indicated that, for the current water year (October-November 2010), the western portion of the UCRB has received plenty of moisture, with several counties in Utah receiving over 200 percent of average precipitation and the Colorado headwaters region over 100 percent. However, for the water year, and also for the month of November, the eastern plains of Colorado, the Rio Grande basin, and the four-corners region have been abnormally dry. As of December 4th, about three-fourths of the USGS streamgages in the UCRB recorded normal or above normal 7-day average streamflows. Though an increasing number of streams have frozen over, the majority of gages that were still recording showed decent 7-day average flows for this time of year. The Colorado headwaters region had the highest density of gages reporting below normal flows. Soil conditions continued to deteriorate just east of the UCRB, in the plains of Colorado, and dry soil conditions were also evident in northwestern New Mexico. Most of the reservoirs in the UCRB stayed fairly steady. Only Lake Powell, Lake Dillon, and Green Mountain Reservoir were below average for early December. Even though below average, both Lake Dillon and Green Mountain saw November releases that were much less than normal releases for this time of year. Many of the other reservoirs also experienced much smaller releases than is normal for November. Lake Powell (currently at 78 percent of average and 62 percent of capacity) released more than what was projected for November, but inflows into the reservoir were also greater than projected.
Arizona: According to the Arizona Department of Water Resources State Drought Monitoring Technical Committee, November was extremely dry across the southern half of Arizona, with less than 5 percent of average precipitation. A few winter storms did cross northern Arizona, bringing rain and snow mostly to the northwestern quarter of the state. The Colorado Plateau, across northeastern Coconino County and central Navajo County, which had been relatively dry last winter, was once again being passed over by the winter storms. This is reflected in an enlarged area of D1, moderate drought, on the November 30 USDM map. Across much of Arizona the vegetation has entered a dormant stage, so precipitation received at this time is more important to water resources than agriculture or rangeland conditions.
The long-term drought situation benefitted from the wet El Niño winter of 2009-2010, particularly at the higher elevations along the Mogollon Rim, the White Mountains in eastern Arizona and across northern Arizona. This brought the Upper Colorado, Upper Gila, Lower Gila, and Salt River watersheds out of drought. Most other watersheds in northern and central Arizona also improved by one or two categories. Southern Arizona did not benefit as much from last year's El Niño winter, but some watersheds with higher elevations experienced a wet monsoon this year, particularly in the southeast quadrant. The Santa Cruz, San Pedro, and Willcox Playa watersheds all improved one category. The San Simon and White Water Draw remained in moderate drought. Few improvements are anticipated this winter, especially in southern Arizona, as a strong La Niña has developed in the central Pacific Ocean, which is associated with a drier than normal winter across the southern United States. While Arizona's reservoirs were nearly full, groundwater basins have only partially recharged, and the Colorado River reservoirs, Lakes Powell and Mead, are quite low. Without an exceptionally wet winter, there could be a shortage on Lake Mead by 2013, according to the Bureau of Reclamation.
The Arizona Drought Interagency Coordinating Group met in early November and recommended that both drought declarations be kept in place:
- Drought Emergency Declaration (PCA 99006) has been in effect since June 1999 and maintains the state's ability to provide emergency response if needed. It also enables famers and ranchers to obtain funding assistance through the Farm Service Agency if they experience production losses due to drought.
- The Drought Declaration for the State of Arizona (Executive Order 2007-10) was issued in May 2007 to raise awareness of Arizona's continuing long-term drought and encourage conservation.
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.
Drought conditions eased in some parts of Hawaii. Windward slopes in the state generally received near to above normal rainfall totals during November. Drought-affected leeward areas also received some rainfall to help provide limited degrees of drought relief. The most significant areas of improvement included the southern portion of the Kau District on the Big Island and the southeast corner of Kauai. The improvement in Kau warranted going from exceptional drought (D4) to extreme drought (D3). November rainfall also helped southeast Kauai go from extreme drought (D3) conditions to severe drought (D2).
Exceptional drought continued over the lower elevations of the South Kohala District of the Big Island with extreme drought extending into the pasture lands farther upslope. A band of severe drought over the leeward upper slopes connected the Big Island's two extreme drought areas. Drought conditions over leeward areas of Maui County remained unchanged. Exceptional agricultural drought persisted over the lower leeward slopes of Haleakala from Kaonoulu to Kamaole near Kihei. Extreme agricultural drought continued over leeward west Maui, the western half of Molokai, and all of Lanai.
Although some improvements have occurred, the ongoing drought has significantly affected a wide range of agricultural products, including cattle, coffee, avocados, rambutan, bananas, corn, macadamia nuts, loquat, and jaboticaba. Only drought-resistant trees and crops have managed to produce well. Some drought impacts in Hawaii include the following:
- Pastures along the lower elevations of the eastern and southeastern sections of Kauai have shown signs of recovery in recent weeks. However, more rain is needed to sustain growth before the drought can be declared over for the island's ranchers.
- On Oahu, Waimanalo Reservoir levels have continued to increase over the past month due to improved rainfall conditions and mitigation measures by agriculture officials. However, a mandatory 30 percent cutback in irrigation water use and a reduction in service hours remained in place as a precaution.
- No significant changes have occurred on Molokai since November 4th. Trade wind rainfall has mainly benefited the eastern half of the island. However, the western half continued to have poor pasture and general vegetation conditions. A mandatory 30 percent cutback in irrigation water use remained in effect for farmers supplied by the Kualapuu Reservoir.
- No significant changes have occurred on Lanai since November 4th. Pasture and general vegetation conditions remained poor. The ongoing drought has forced cattle ranchers to ship feed in from off-island resulting in financial impacts.
- There have been no significant changes since November 4th on Maui. Pasture losses have exceeded 90 percent in the lower elevations of southwest Maui from Kaonoulu to Kamaole. Resultant livestock losses in this area were also very high. Pastures and general vegetation conditions were very poor over the remaining leeward areas of the island and herd culling has exceeded 30 percent in some areas. Abundant trade wind rainfall during November kept supply levels high for upcountry Maui. However, as a precaution, the Maui County Department of Water Supply continued to request a 5 percent reduction in water use by upcountry residents, and a 10 percent reduction in water use by central and south Maui residents.
- On the Big Island, November rainfall helped produce improvements in drought conditions in the Lower Kau District from South Point to Kapapala. However, the lower slopes of the South Kohala District remained very dry. Ranchers in the area have been operating under very poor conditions and were hauling water and feed for livestock sustenance.
Precipitation varied on other Pacific Islands. Weather and cooler-than-normal sea surface temperatures associated with the moderate to strong La Niña resulted in drought conditions along the equator extending from about 150 degrees East longitude to at least the International Date Line. This area included the Micronesian islands of Kapingamarangi Atoll and Nauru, and the atolls of western Kiribati.
In the Federated States of Micronesia, adequate rainfall has occurred for most of Pohnpei state, but weather has remained very dry at Kapingamarangi over the last 5 to 6 months (Kapingamarangi is a southern island in Pohnpei state, near the equator). The average rainfall on Kapingamarangi for July-November is 34.86 inches. For July-November 2010, Kapingamarangi received 11.56 inches of rain, or a third of average. For the last 3 months, September-November, Kapingamarangi received only 3.89 inces of rain, or 21 percent of normal. On November 15, the Pohnpei Disaster Control Office indicated that the catchments on Kapingamarangi were out of water. Subsequent mid-November rains added a few gallons of water to the catchments, and wells and solar stills produced some water for drinking and cooking. But some damage to food crops may have occurred on Kapingamarangi Atoll as a result of the drought. Continued implementation of stringent water conservation measures on the island was encouraged. Kosrae had 84 percent of average rainfall for September-November 2010 and Nukuoro had 73 percent. September-November rainfall averaged across Pohnpei state was 89 percent of the long-term average. Rainfall in Chuuk state was a little below normal for November. Yap state received adequate rainfall during the summer, although November was below normal. Yap is starting its transition into the dry season.
On other Pacific Islands, Guam had 4.38 inches of rain for November, or half of normal. The very dry conditions are related to the lack of Pacific tropical cyclones. American Samoa experienced near normal rainfall, while enhanced convection contributed to heavy rainfall the first half of the month on Kwajalein. In spite of a dry second half of the month, November rainfall was 158 percent of normal for Kwajalein. Rainfall was near normal on Majuro with reservoirs remaining full during the last couple months. Parts of the Commonwealth of the Northern Mariana Islands (CNMI), specifically around Tinian, were drier than normal. This exemplified sharp variability over distances of 100 miles or less in the region.
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