National Drought Summary -- July 3, 2012
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/.
Weather Summary: Overall, this week featured the expansion and intensification of dryness in large sections of the country, with only southern Texas reporting some improvement. Light precipitation (0.5 inch or less) fell on most areas of dryness and drought, with only scattered areas reporting more than an inch, primarily in the northern Plains, lower Mississippi Valley, southernmost Great Lakes region, Appalachians, mid-Atlantic region, and southern Texas. This despite a couple of thunderstorm complexes that pushed rapidly from northern Illinois east-southeastward through the mid-Atlantic, including one on June 29 that caused significant damage, knocked out power for millions of customers, and took 2 dozen lives. Unfortunately, where rain did fall (outside southern Texas), it was not enough to make up for blistering heat that covered the Nation’s midsection, reaching the central and southern Atlantic Coast by the end of the workweek. Both the number of record highs in the past week, and the areas with record and near-record dryness over the last 1 to 3 months, are too numerous to mention. Daily high temperatures averaged above 100 degrees in the central and upper southern Plains, extending eastward into parts of Missouri and Arkansas, and average temperatures for the week were 8 to locally 15 degrees above normal from the Ohio Valley and upper Southeast westward through most of the High Plains. The dryness is beginning to take a significant toll on some of the Nation’s crops, pastures, and rangelands. In the primary growing states for corn and soybeans (18 each), 22 percent of the crop is in poor or very poor condition, as are 43 percent of the Nation’s pastures and rangelands and 24 percent of the sorghum crop. In addition, the area scorched by wildfires expanded significantly. Over 1.9 million acres have been engulfed since the start of the year, and increase of 38 percent in just the past week.
The Northeast and Mid-Atlantic: Despite a couple of thunderstorm complexes that brought light to locally moderate rain to parts of the region, the late-period hot weather across the mid-Atlantic and a return to dry weather over the last couple of weeks allowed D0 conditions to expand through much of this region, with a few patches of moderate drought showing up. Farther north, there was some limited expansion of D0 and, in western Pennsylvania, D1 conditions.
The Tennessee Valley, Southeast, Deep South, and lower Ohio Valley: Brutal heat and only light to locally moderate rain engendered a broad expansion and intensification of dryness and drought. Most of this region recorded less than half of normal precipitation during the last 30 days, with under 25 percent of normal falling on the lower Ohio Valley, much of Kentucky and northern Tennessee. Indiana, Missouri, Kentucky, and Tennessee each have 45 to 50 percent of their corn crop in poor or very poor condition as well as 34 to 49 percent of soybeans.
The Mississippi Valley Westward to the Pacific Coast: Another hot and dry week led to rapid deterioration and expansion of dryness and drought from the Rockies eastward. The only exception was southern Texas, where many locations recorded 1 to 3 inches of rain, leading to areas of improvement in the widespread D1 to D3 conditions. Farther north, D0 to D3 conditions expanded, with exceptional dryness (D4) developing in parts of north-central and east-central Colorado. In New Mexico, 59 percent of the Sorghum crop is in poor or very poor condition, and much of the region’s rangeland is in similarly bad shape, including 74 percent of rangeland in Arizona, 77 percent in Colorado, and 89 percent in New Mexico. In addition, the now-infamous Waldo Canyon Fire in Colorado, though partially contained, has been called the most destructive wildfire in the state’s history by local officials. Farther north, the Nation’s largest wildfire rages in Montana’s Custer National Forest, having consumed approximately 186,000 acres as of this writing. Dryness and heat were less exceptional from the Intermountain West westward to the Pacific Coast. No changes in dryness or drought were introduced there.
Hawaii and Alaska: Between 1 and 3 inches of rain fell on east-central Alaska while little or none fell on the state’s northern tier. This engendered some slight improvement in southeastern sections of the D0 region, but it seems insufficient to have completely eliminated that region’s dryness. In the dry areas across Hawaii, many locations reported 1 to locally over 3 inches of rain in southwestern sections of the Big Island, east-central Maui, and some of central and southeastern Oahu. Other D0 to D3 areas reported only light precipitation, if any. The continuing dryness in the southeastern half of Kauai, where cattle ranchers are reporting that drought stress has started, was degraded to moderate drought (D1), and the rest of the state was unchanged.
Looking Ahead: In general, July 4 – 8, 2012 doesn’t look promising in terms of relief, though the intense heat should subside somewhat. One area that could see relief would be from the central and southern Rockies into the northern Plains, much of which is forecast to receive over an inch of rain. Totals near or above 2 inches are expected in the central Dakotas. One to perhaps 3 inches are also anticipated along and near the central Gulf Coast. Elsewhere, light rain at best is expected, with little or none forecast for the lower Northeast, the mid-Atlantic region, the upper Southeast, the Ohio Valley, much of the Mississippi Valley, and the central and southern Plains. Seasonably dry weather is expected in the West. Modest improvement is forecast for most areas that have endured the recent heat wave, but most locations from the Plains eastward are still expected to be warmer than normal. Temperatures could average over 6 degrees above normal from the mid-Atlantic region westward through the Tennessee and Ohio Valleys to near the Mississippi River.
The ensuing 5 days (July 9 – 13, 2012) bring enhanced chances for below-normal rainfall from the Tennessee and middle Mississippi Valleys northward through the Appalachians, Great Lakes, and northern Great Plains. In contrast, the odds favor above-normal rainfall along and near the southern half of the Atlantic Coast and in the southern halves of the High Plains and Rockies. Below-normal temperatures are expected to settle into the Northeast, but continued above-normal temperatures are anticipated in the southern halves of the Mississippi Valley and eastern Plains, and from the northern Plains, the central Rockies, and the desert Southwest westward to near the Pacific Coast.
Author: Rich Tinker, Climate Prediction Center, NCEP, NWS, NOAA 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
S ... Short-Term, typically <6 months (e.g. agricultural, grasslands)
L ... Long-Term, typically >6 months (e.g. hydrology, ecology)