8/23 Drought Monitor; Pasture 90%, 96% Poor/Very Poor In OK, TX; D2-D4 Conditions Span Southern KS

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National Drought Summary -- August 23, 2011

The discussion in the Looking Ahead section is simply a description of what the official national guidance from the National Weather Service (NWS) National Centers for Environmental Prediction is depicting for current areas of dryness and drought. The NWS forecast products utilized include the HPC 5-day QPF and 5-day Mean Temperature progs, the 6-10 Day Outlooks of Temperature and Precipitation Probability, and the 8-14 Day Outlooks of Temperature and Precipitation Probability, valid as of late Wednesday afternoon of the USDM release week. The NWS forecast web page used for this section is: http://www.cpc.ncep.noaa.gov/products/forecasts/.

Summary: Locally heavy showers provided drought relief in the nation’s mid-section and across the Atlantic Coast states. In contrast, increasingly hot, dry weather mitigated the benefits of recent rainfall on the southern Plains.

Mid-Atlantic and Northeast: For a second consecutive week, locally heavy showers further improved drought conditions across much of the region. In particular, rainfall totals in excess of 2 inches (pushing two- week totals in many areas over 5 inches) eased or eradicated lingering drought across central and eastern Maryland and adjacent portions of Delaware. Rain (0.5 to 2 inches) in western New York also provided some additional relief from Moderate Drought (D1). However, coastal portions of New England, where soil moisture percentile rankings indicated ongoing Abnormal Dryness (D0), largely missed this week’s rainfall. Farther inland, 60- to 90-day precipitation continued to run less than 50 percent of normal across eastern West Virginia and western and northern Virginia, with declining streamflows and soil moisture supporting an increase of D0.

Southeast and Mississippi River Delta: A narrow but heavy band of rain (locally more than 5 inches) provided some additional relief from Moderate to Severe Drought (D1 and D2, respectively) along the North Carolina/South Carolina border. In Florida, widespread, locally heavy showers (2 to 5 inches) likewise supported additional improvements from drought, most notably in southern and eastern portions of the peninsula. In contrast, central and northeastern Alabama wrestled with increasingly dry conditions, with little if any rainfall over the past 30 days causing streamflows and soil moisture to decline. Consequently, drought designation was increased in these parts of the state. In southeastern Tennessee and northern Georgia, precipitation deficits continued to mount, with 90-day rainfall now standing at 25 to 50 percent of normal; therefore, Moderate Drought (D1) was introduced to reflect the precipitation shortfalls and rapidly declining soil moisture and streamflow percentile rankings. In the Delta, scattered, mostly light showers in southern portions of the region were insufficient to provide drought relief. Additionally, hot weather (highs reaching 105-108°F) in the southern Delta increased evaporative losses, and rain will be needed to soon to prevent drought conditions from worsening. Rain was somewhat heavier (locally up to 2 inches) in northern sections of Mississippi and Arkansas, resulting in small improvements in the overall drought situation.

Ohio Valley and Midwest: Abnormally dry conditions have persisted over the past 60 days from eastern South Dakota eastward into southern portions of Minnesota and Wisconsin as well as adjacent portions of northern Iowa and Illinois. Many areas have reported less than 50 percent of normal rainfall during this timeframe, with some locales reporting less than 25 percent of normal. Consequently, D0 was expanded across most of this region, as crop conditions continued to reflect the impacts of the drier-than-normal weather. However, a narrow band of showers and thunderstorms sliced through the middle of the new Abnormally Dry region, dropping locally more than an inch of rain. In Indiana, expansion of Moderate Drought (D1) was a reflection of increasing precipitation deficits over the past 60 days, with rainfall running 4 to 6 inches below seasonal norms (25-50 percent of normal). Farther south and west, moderate to heavy rain swept southeastward out of eastern Nebraska and southwestern Iowa into Missouri and northeastern Kansas. Totals exceeded 2 inches over a large area, with some locations receiving more than 5 inches. As a result, reductions in drought intensity were made in the areas of heaviest rain.

Southern Plains: In Texas and southern Oklahoma, above-normal temperatures (up to 11°F above normal, with highs eclipsing 105°F) and sunny skies rapidly offset the benefits of early month rainfall. Consequently, after recent localized improvements, drought intensified over many of the remaining D2 and D3 areas (Severe to Extreme Drought), with the vast majority of Texas and Oklahoma back under Exceptional Drought (D4). To point, pasture and range condition was rated 90 and 96 percent poor to very poor in Oklahoma and Texas, respectively, as of August 21. 180-day rainfall deficits exceeded 12 inches in southwestern Oklahoma and north-central Texas, and were locally in excess of 20 inches along the southeastern Texas coast. Farther north, scattered, mostly light showers offered little if any relief from Severe (D2) to Exceptional (D4) Drought from southern Kansas into southeastern Oklahoma, where daytime highs likewise rose well into the lower 100s (degrees F). Severe Drought (D2) was expanded eastward across southeastern Kansas to account for declining streamflow and soil moisture percentiles, as well as increasingly dry conditions out to 90 days (locally less than 50 percent of normal). Rain will be needed soon to ensure sufficient soil moisture for winter wheat planting and establishment.

Northern Plains: Despite a mostly dry week, cooler-than-normal conditions (2 to 7°F below normal) along with recent abundant rainfall kept most of the region out of drought or Abnormal Dryness (D0). The pocket of D0 in southwestern South Dakota and northeastern Wyoming remained unchanged.

Four Corners Region: Moderate to heavy showers (locally more than 2 inches) provided some relief from Moderate to Exceptional Drought (D1 to D4) from southeastern Colorado into southwestern New Mexico and southeastern Arizona. Drought reduction was most pronounced in southeastern Colorado and northeastern New Mexico, where rain was heaviest. In addition, updated soil moisture percentiles and Standardized Precipitation Indices (3 to 6 month) indicated much of the Extreme and Exceptional Drought had abated due to recent rainfall. Remote-sensing data (Vegetation Health Index and the VegDri Index) likewise indicated recent greening in the aforementioned areas. In contrast, short-term dryness across the High Plains of central Colorado reduced soil moisture for winter wheat planting, with D0 added to this area to account for the increasing concern.

Alaska, Hawaii, and Puerto Rico: In Alaska, light showers (mostly less than an inch) and near-normal temperatures were reported, with no change made to the southern Abnormally Dry (D0) area. In Hawaii, Moderate Drought (D1) was expanded eastward on the Island of Maui to reflect declining pasture conditions. There were no changes made elsewhere in Hawaii. On Puerto Rico, heavy rain from Hurricane Irene resulted in flooding, with no dryness or drought concerns likely over the upcoming weeks (or longer).

Looking Ahead: While interests in the eastern U.S. will closely monitor the path and intensity of Hurricane Irene, the rest of the nation will contend with mostly dry, warmer-than-normal weather. Irene’s final track will determine how rain falls in drought areas from Georgia northward into the Mid-Atlantic and Northeast; current projections suggest most of the heavy rain will be along the coast and immediate environs. Somewhat cooler conditions will prevail in the Corn Belt, while most of the Plains, Mississippi River Delta, and Southeast will experience late-summer heat. Scattered showers are possible from the Dakotas southward into Kansas and central Oklahoma, but the rain is not expected to be heavy enough to provide much – if any – drought relief. Potentially heavy monsoon showers are possible in northern New Mexico and Colorado. The NWS 6- to 10-day outlook for August 30 – September 3 calls for drier- and warmer-than-normal conditions across much of the nation, with the greatest likelihood of heat and dryness centered over the south-central U.S. Above-normal rainfall will be confined to the northern-most Plains, while cooler-than-normal conditions will be limited to the Pacific Coast states.

Author: Eric Luebehusen, U.S. Department of Agriculture, and Laura Edwards, Western Regional Climate Center

Dryness Categories

D0 ... Abnormally Dry ... used for areas showing dryness but not yet in drought, or for areas recovering from drought.

Drought Intensity Categories
D1 ... Moderate Drought
D2 ... Severe Drought
D3 ... Extreme Drought
D4 ... Exceptional Drought

Drought or Dryness Types
A ... Agricultural
H ... Hydrological



Updated August 24, 2011

http://droughtmonitor.unl.edu/