This Week's Drought Summary (5/30)

May 30, 2019


During this U.S. Drought Monitor (USDM) week, a strong high pressure ridge was anchored over the southeastern contiguous U.S. (CONUS) while an upper-level trough dominated the West. This pattern set up a southwesterly flow across the central part of the country, which funneled moist and unstable air from the Gulf of Mexico into the Plains. Pacific weather systems moving in the jet stream flow plunged into the western trough, bringing precipitation and cooler-than-normal temperatures to much of the country from the Rockies westward. The weather systems intensified as they moved into the Plains, triggering another week of severe weather and heavy flooding rains. Two or more inches of precipitation occurred across the Plains to Midwest and in upslope areas of Montana and Wyoming, with locally 5 inches or more. Weekly precipitation was wetter than normal across much of the Southwest, and from much of the Great Plains to Great Lakes. Half an inch to locally 2 inches was observed from the central Appalachians to New England, but these amounts were mostly below normal. The week ended up drier than normal across western Washington, northern Idaho and northern Montana, southern Arizona, most of New Mexico, and central to southern Texas. The subtropical high kept the Southeast drier and warmer than normal, with record high temperatures reported. As a result of this weather pattern, drought contracted in Oregon, Wyoming, and the central Plains, but expanded in the northern Rockies, Texas, the Tennessee Valley, and the Southeast.


This week was drier than normal for much of the Northeast, with dry areas developing over the last 3 months. Pockets in New England were nearing a 3-inch precipitation deficit over the last 90 days. While the region is currently free of drought or abnormal dryness on the USDM map, D0 could be added in the coming weeks if below-normal precipitation persists.


The subtropical ridge left most of the Southeast with no rainfall this week and several record maximum temperatures. The hot weather increased evaporation and dried soils. Only isolated areas, mostly in the Carolinas and Florida, had any rain at all and amounts were mostly less than half an inch. D0-D1 expanded from northern Florida to southern Virginia. Dry and hot conditions prevailed for the last 2 to 4 weeks, with below-normal precipitation noted in many areas for the last 3 months. Some of the drought indicators, especially the Standardized Precipitation Index (SPI), Evaporative Drought Demand Index (EDDI), and soil moisture indices, indicated D2 was imminent, but D2 was not added this week. May 26 U.S. Department of Agriculture (USDA) reports indicated that 77% of the topsoil moisture in Georgia was short or very short (dry or very dry), up from 41% last week. Other states had similar increases: Alabama increased from 12% to 47%, Florida increased from 42% to 64%, North Carolina increased from 29% to 60%, South Carolina increased from 48% to 86%, and Virginia increased from 3% to 26%. Subsoil moisture conditions were just as bad, with short to very short subsoil up to 33% of Alabama, 52% of Florida, 55% of Georgia, 14% of Mississippi, 50% of North Carolina, and 76% of South Carolina. According to media reports, Brunswick County in southeastern North Carolina issued a notice to "use water wisely" due to developing drought conditions and increased demand, and was considering instituting water conservation measures. Nearby Pender County restricted water use due to an ongoing water shortage emergency in southeastern parts of the county caused by high demand, hot weather, and limits in their distribution system. In Georgia, reports from Coffee County included hay reserves disappearing, soils drying, and heat stress to crops; planting stopped on non-irrigated acres and irrigation was turned on for irrigated acres.


Precipitation amounts in the South ranged from zero in parts of Texas, Louisiana, Mississippi, and Tennessee, to over 5 inches in northern Oklahoma. D0 expanded in central Tennessee where 90-day precipitation deficits were noteworthy, pockets of D0 expanded or were introduced in southern Texas along the Rio Grande or along the coast, and D1 was added to Zavala County in Texas where dryness was evident for the last 7 days to 6 months. According to USDA reports, 21% of the topsoil moisture in Tennessee was short or very short, up from 3% last week. The last couple weeks have been very dry, hot, and windy in southern Texas as the subtropical ridge continued to build and dry out the atmosphere. There have been reports of significant evaporation of Cameron County retention ponds with fields and lawns showing some browning. Some producers in Dimmit County, Texas were hauling water and supplemental feeding in some areas.


Precipitation this week in the Midwest ranged from widespread 2+ inches in the western portions to less than an inch in the eastern portions and a tenth of an inch or less along southern Kentucky. D0 expanded into Kentucky from Tennessee where 7-90 day precipitation deficits were significant, and a small area of D0 continued in northwest Minnesota. Otherwise, the Midwest region was devoid of drought or abnormal d