8/30 Drought Monitor; Cotton 60% Poor/Very Poor OK; 92% TX; D3 Returns To GA, AL

[hatrack]

National Drought Summary -- August 30, 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: Hurricane Irene brought widespread, locally excessive rainfall to the mid-Atlantic and Northeast, while heat and dryness maintained or worsened drought conditions across the central and southern U.S.

Mid-Atlantic and Northeast: Hurricane Irene tracked northward along the mid-Atlantic Coast into New England, dropping moderate to heavy rain – in some cases excessive rainfall – from eastern North Carolina into New England. Rain amounts tallied 4 to locally more than 12 inches over eastern sections of North Carolina, Virginia, Maryland, most of Delaware, and New England, eliminating drought and lingering long-term dryness in one sweep. Some Abnormal Dryness (D0) and Moderate Drought (D1) were maintained in central and southern sections of North Carolina, where precipitation was somewhat lighter (generally less than 4 inches), and consequently long-term deficits persist. Showers (locally more than an inch) and improving streamflows and soil moisture led to the removal of D1 from western New York and a reduction of the coverage of D0, although here, too, longer-term (90-day) rainfall was still locally less than 50 percent of normal. Farther inland, 60- to 90-day precipitation continued to run less than 50 percent of normal from eastern West Virginia into southwestern North Carolina, with declining streamflows and soil moisture supporting an increase of D0 and D1.

Southeast and Delta: With Hurricane Irene passing well off the southern Atlantic coast, generally dry, hot weather (2 to 5°F above normal) prevailed over much of the region. However, additional improvements in drought designation were noted in eastern and southern Florida, where favorable seasonal showers continued. Across northern Florida, mostly light showers (less than one inch) did little to offset the100-degree heat; rain will be needed soon in northern Florida to ensure drought conditions do not rapidly worsen. From western South Carolina into Georgia, Alabama, Tennessee, and Florida’s panhandle, sunny skies and daytime highs approaching or exceeding 100°F caused drought to intensify. Most notably, Extreme Drought (D3) expanded across southern Georgia, the Florida Panhandle, and central Alabama, reflecting streamflows that were approaching or at historic lows, as well very low soil moisture and poor vegetation health. As of August 29, Georgia’s pasture and range condition was rated 62 percent poor to very poor. Similar conditions were reported farther west, where Severe (D2) to Exceptional (D4) drought expanded in southern portions the Delta. In the northern Delta, an area of light to moderate showers (0.5 to 2.5 inches) kept drought from intensifying from southern Missouri into central Arkansas and northern Louisiana. In Tennessee, Moderate Drought (D1) was increased in eastern parts of the state, where streamflows were ranked in the 10th percentile or lower. The same held true in western Tennessee, where D1 was likewise introduced.

Ohio Valley and Midwest: Despite being one of the few locales to experience near- to in some cases below-normal temperatures, drought intensity increased over many primary growing areas. Abnormally dry conditions have persisted over the past 60 days from southeastern Minnesota into southern Wisconsin (locally less than 50 percent of normal), with Abnormal Dryness (D0) expanded to account for the lack of rainfall and declining soil moisture. More notably, 60-day precipitation has tallied less than 25 percent of normal (locally less than 10 percent) from southeastern Iowa into central Illinois and southern Indiana; Severe Drought (D2) was added to areas with the greatest precipitation departures and impacts. Likewise, abnormal dryness over the past 90 days (50 percent of normal or less) led to a new D1 area in northeastern Minnesota. In contrast 1 to 2.5 inches of rain in Ohio eased Abnormal Dryness in northwestern portions of the state.

Northern and Central Plains: From the Dakotas and eastern Montana into Nebraska and northern Kansas, scattered showers mingled with pockets dryness, leading to generally small changes in the current drought depiction. Light to moderate rainfall (0.75 to 2.0 inches) in northeastern Nebraska and southeastern South Dakota resulted in small improvements in Abnormal Dryness (D0) and Moderate Drought (D1). Showers (locally more than 2 inches) were reported in southwestern South Dakota and northwestern Nebraska, although above-normal temperatures (highs reaching into the lower 100s degrees F) offset the benefits of the rain somewhat. Short-term dryness and above-normal temperatures (up to 9°F above normal) in western Nebraska led to the introduction of a small D0 area. Short-term dryness (out to 60 days) has likewise been reported in eastern Wyoming, and this area will need to be monitored for developing drought. On the high Plains of Colorado, D0 was expanded slightly northeastward due to a lack of rain over the past 30 to 60 days, low Standardized Precipitation Indices (SPI), declining soil moisture, and an increasingly poor VegDri signal.

Southern Plains: The beat goes on across the southern Plains. In Texas and southern Oklahoma, another week of above-normal temperatures (up to 14°F above normal, with highs eclipsing 110°F) and sunny skies further offset the benefits of early month rainfall. Consequently, drought intensified over many of the remaining D2 and D3 areas (Severe to Extreme Drought), with the vast majority of Texas and Oklahoma under Exceptional Drought (D4). As of August 29, pasture and range condition was rated 98 and 92 percent poor to very poor in Texas and Oklahoma, respectively. Further illustrating the heat and drought’s devastating impacts, cotton – a crop that generally thrives in hot, dry weather – was rated 60 percent poor to very poor in Texas and an astounding 92 percent poor to very poor in Oklahoma. 180-day rainfall deficits exceeded 14 inches in southwestern Oklahoma and north-central Texas, and were locally in excess of 20 inches near Houston. Farther east, scattered, mostly light showers offered little if any relief from Severe (D2) to Exceptional (D4) Drought from eastern Oklahoma into eastern and far southern Texas.

Four Corners Region: Drought relief over northeastern portions of the region contrasted with an increase in drought designation in southwestern locales. Beneficial showers (1 to 2 inches) further improved soil moisture in northern New Mexico as well as southern and eastern Colorado; consequently, the coverage of Moderate (D1) to Extreme (D3) Drought was reduced in these areas to reflect the most current Standardized Precipitation Indices (3, 6, 9, and 12 month). The coverage of Colorado’s Exceptional Drought (D4) was virtually unchanged, with small modifications made to account for the updated VegDri Index as well as the most recent precipitation data. Environs within the core D4 area are still below 25 percent of normal precipitation over the past 180 days, although additional local analysis and input may lead to changes in drought designation over the upcoming weeks. Abnormal Dryness (D0) on the High Plains of Colorado was expanded slightly northeastward due to a lack of rain over the past 30 to 60 days, a low 3-month Standardized Precipitation Index, declining soil moisture, and increasingly poor VegDri Index. In southern and western Arizona, expansion of Moderate (D1) to Extreme (D3) drought was a reflection of a drier-than-normal monsoon to date (less than 50 percent of normal rainfall over the past 90 days). Temperatures over southern and western Arizona averaged 9 to 13°F above normal during the past week, exacerbating the impacts of the drier-than-normal weather. Furthermore, Standardized Precipitation Indices on numerous timescales (3 to 12 months) indicated developing or expanding drought in western Arizona. Dryness has also increased in central and southeastern portions of Nevada as well as much of the Northwest, and these areas will need to be monitored closely over the upcoming weeks.

Alaska, Hawaii, and Puerto Rico: In Alaska, light showers (mostly less than half an inch) and near-to below-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 Lanai to reflect declining pasture conditions and reports from the field. There were no changes made elsewhere in Hawaii. On Puerto Rico, flood recovery efforts following Hurricane Irene’s heavy rain continued, with no dryness or drought concerns likely over the upcoming weeks (or longer).

Looking Ahead: The evolution and track of a developing tropical disturbance in the Gulf of Mexico will be closely monitored. This system – should it develop – could play a potentially large role in whether portions of the southern or southeastern U.S. experience much-needed drought relief over the upcoming week. Elsewhere, a slow-moving cold front will generate showers from the northern and central Plains into the Corn Belt and Northeast, with some showers spilling south into Oklahoma and Texas. Out west, monsoon showers will persist in eastern portions of the Four Corners region, while dry, increasingly warm weather prevails from the Great Basin into the northern Rockies and Northwest. The NWS 6- to 10-day outlook for September 6–10 calls for drier-than-normal conditions from the central and northern Pacific Coast into the upper Midwest and central Corn Belt. Conversely, wetter-than-normal weather is expected from the eastern Gulf Coast into the Northeast. Below-normal temperatures across much of the eastern U.S. will contrast with warmer-than-normal weather from the Rockies to the Pacific Coast.

Author: Eric Luebehusen, U.S. Department of Agriculture

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

http://droughtmonitor.unl.edu/

[xchrom]

1. recommend