A high pressure ridge in the jet stream flow kept the West warmer than normal and quite dry. A trough in the East with its surface lows and fronts brought above-normal rain to parts of the southern Plains, Midwest, and Southeast to Northeast. Above-normal precipitation fell across southern Arizona, courtesy of the summer monsoon, while the monsoon under-performed across the rest of the Southwest this week. Temperatures were warmer than normal with little rainfall across the northern Plains to Great Lakes. The week ended with a cutoff closed low meandering across the southern Plains and moving into the central Plains, leaving heavy rain and below-normal temperatures in its wake. The continued dryness in the West and northern Plains expanded drought and abnormal dryness, while the rains in the south reduced drought intensity and/or area.
Continued dryness, low soil moisture, and some low stream levels prompted the expansion of D0 westward and northward in Puerto Rico. Wildfires continued in parts of Alaska where precipitation has been below normal for various time scales from the last 30 days to 6 months. But precipitation was above normal this week in these areas, as well as parts of the northern panhandle. Drier-than-normal weather continued for parts of Hawaii this week, while other parts were wetter than normal. No changes were made to the USDM depiction for Alaska and Hawaii.
Above-normal rains from the upper-level low reached parts of Kansas by the Tuesday morning data cutoff time, but the rest of the region was much drier than normal, with little rainfall reported. D0-D2 were contracted in central and southern Kansas, but the northeast part of the state was still drier than normal for the week. D2-D4 expanded in northeast Kansas, and D0-D1 were expanded in southeast Nebraska, to reflect dryness at the 3 to 9-month time scale. D0-D1 expanded, and D2 was introduced, in the Dakotas. A weaker-than-normal monsoon, coupled with record 1-month evaporative demand due to high temperatures, have stressed vegetation and lowered streamflows in Colorado. D0 was trimmed slightly in eastern Colorado where it has been wet, but D2-D3 expanded in the northwest to central region where precipitation deficits mounted and stream levels were low. According to August 12 USDA reports, 59% of the pasture and rangeland in Colorado was in poor to very poor condition, and 42% of the topsoil was short or very short of moisture; 35% of the pasture and rangeland in Kansas was in poor to very poor condition. As noted by the South Dakota State Climatologist, the lack of rain and high evaporation accompanying hot temperatures have taken a toll on crop conditions in the central and north central regions. Impacts include soybeans, which are in a critical time for grain fill, are flipping their leaves to reduce water use/loss, corn is turning brown and dead in places, and stock ponds are at very low levels. Statewide, according to USDA reports, 16% of the pasture and rangeland in South Dakota is in poor to very poor condition and 38% of topsoil and 39% of subsoil is short to very short of moisture.
Above-normal precipitation fell across parts of Ohio, Kentucky, southeast Michigan, and southern Illinois, and rain from the cutoff upper low over the southern Plains began to spread into southwestern Missouri right at the Tuesday morning data cutoff time. But most of the Midwest was dry this week. D0-D1 were trimmed in northwest Ohio and adjacent southeast Michigan. But drought and abnormal dryness expanded or were introduced in all of the states except Ohio. D1 was introduced or expanded in northern Illinois, southern Iowa, northern Minnesota, southwest Michigan, and western Wisconsin. Missouri is the epicenter of drought in the Midwest. Parts of the state have had very hot and dry weather in recent weeks and months, and some parts have been dry for the last year or longer. As a result, D0-D4 were expanded across much of the state. Drought impacts in Missouri, as noted by the NDMC, include weekly cattle sales at the St. Joseph Stockyards have been about 600 head recently, in comparison with typical sales for this time of year of 50 to 60 cattle weekly; low water levels and poor hay production were driving the sales. Forages were dormant in central Missouri, leaving producers to feed hay or find other food sources. According to August 12 USDA reports, 45% of the corn crop, 37% of the soybean crop, and 76% of the pasture and rangeland in Missouri were in poor to very poor condition, and 79% of the topsoil and 80% of the subsoil was short or very short of moisture; 32% of the pasture and rangeland in Michigan was in poor to very poor condition, and 54% of the topsoil and 58% of the subsoil was short or very short of moisture; 22% of the pasture and rangeland in Illinois was in poor to very poor condition, and 40% of the topsoil and 41% of the subsoil was short or very short of moisture; 28% of the pasture and rangeland in Iowa was in poor to very poor condition, and 36% of the topsoil was short or very short of moisture. Reports received by the Iowa State Climate Office include depleted ponds, dry creek beds, and brown pastures in south central counties.
The week was drier than normal across northern portions of New England, and wetter than normal in the southern parts of the Northeast. D0 was trimmed from western Suffolk County on Long Island where 90-day precipitation was above normal, but otherwise no changes were made to the drought depiction in the Northeast. D0-D1 continued in the northern portions. In Maine, dry conditions were affecting wells as groundwater levels continued their slow decline over the summer. According to August 12 U.S. Department of Agriculture (USDA) reports, 31% of the pasture and rangeland in New Hampshire was in poor to very poor condition, and 43% of the topsoil and 45% of the subsoil was short or very short of moisture; 88% of the topsoil and 87% of the subsoil in Vermont was short or very short of moisture. As summarized by the National Drought Mitigation Center (NDMC), water restrictions or water shortages were reported in communities in New York and Massachusetts.
Most of the South was wetter and cooler than normal this week. Heavy rain fell from central Texas to southeast Oklahoma and much of Arkansas. Reports of 4 inches or more of rainfall were common. The rains missed other portions of the region, especially coastal Texas, the panhandles of Texas and Oklahoma, the worst drought areas of southwest Oklahoma, and parts of Louisiana. D0-D3 contracted across much of Texas, Oklahoma, Arkansas, and northern Louisiana. But D0-D4 expanded in parts of Texas and Mississippi which missed the beneficial rains. The resulting pattern of D0-D4 in Texas reflected dryness at several time scales. Based on a crucial drought indicator, the Standardized Precipitation Index (SPI), it was dry at the 30-day time scale in the Trans-Pecos, northern panhandle, and Gulf coast; dry at 60 days in the Trans-Pecos and northern tier counties; dry at 90 days from the southern Rio Grande, across central Texas to the north central and northeast areas; the 120-day timescale is similar to 90 days except there was more severe dryness and includes the Trans-Pecos; 6 months has dryness mostly in west to central Texas, with a spot over the Gulf coast; 9 months is the 6 month pattern except lots drier; 12 months is like 6 and 9 months; 24 months has some spotty dryness mostly central to north central and northeast. When soils are parched from dryness of these timescales, a one-week rainfall of 4 inches is helpful, but not a drought-buster. As summarized by the NDMC, water restrictions or water shortages were reported in Waco and other Texas communities, specifically media reports that recent rain did not improve water supplies in Waco where 50 million gallons on average were used daily this summer. Voluntary water restrictions were taking effect in other central Texas cities like Robinson. By early August, drought impacts in many parts of Texas included pastures and rangeland in poor to very poor condition or declining condition, forage production has stopped, stock ponds receding or low water supplies for livestock, and, in central Texas, total loss of all dryland crops. The rains this week were helpful, but not for the crops that were already lost. According to August 12 USDA reports, 36% of the corn crop and 57% of the pasture and rangeland in Texas were in poor to very poor condition, and 71% of the topsoil and 76% of the subsoil was short or very short of moisture; 29% of the pasture and rangeland in Louisiana was in poor to very poor condition, and 43% of the topsoil was short or very short of moisture; 45% of the pasture and rangeland in Arkansas was in poor to very poor condition, and 50% of the topsoil was short or very short of moisture.
Showers and thunderstorms, triggered by fronts or afternoon convection, left a patchwork of above-normal and below-normal precipitation across the Southeast. A few areas of abnormal dryness dotted the region. But the only change to the map in the Southeast was expansion of D0 areas in Alabama to reflect 1 to 2-month dryness.
Monsoon showers gave southern Arizona drenching rains, but most of the West was drier than normal, with no rain falling across most of the Pacific Northwest and California. The Arizona rainfall improved the percent of normal statistics for the last 1 to 9 months, but there was still significant dryness at the 12-month time scale, and this region has experienced on-and-off drought for much of the last several years. D3 was pulled back in southwest Arizona, and the nearby D4 was deleted, where the heaviest rains fell. D0 expanded in Idaho and Montana, D1 extended down the coast in northern California, D1 expanded in Idaho, D1-D2 expanded in Oregon, and D3 was introduced in southwest Oregon. Lowering streamflows and reservoir storage, and increased fuel load (for wildfires) caused by unusually warm temperatures, increased drought stress in western Idaho. In Oregon, during years with poor winter snowpack and hot and drier-than-normal summers, the water systems for the smaller communities are stressed and run out of water. These water systems are stretched even in good years. As noted by the Oregon State Climate Office, a town in Baker County is running out of water and imposing fines on watering, and getting water shipped in. According to August 12 USDA reports, 63% of the pasture and rangeland in Oregon was in poor to very poor condition, and 90% of the topsoil and 88% of the subsoil was short or very short of moisture (dry to very dry); in southwestern Oregon, many ranchers reported pastures one half of normal production, creeks dried up and several were reported at lower levels than observed in previous drought years. As noted by the NDMC, the dry summer in the Pleasant Hill, Oregon, area has taken a toll on saplings and prevented even mature Christmas trees from growing much; Washington residents reported unusually high numbers of dead and dying Douglas-fir trees to the Washington State Department of Natural Resources this spring and summer as drought and bark beetles ravaged the trees; and water restrictions or water shortages were reported in eastern and northern Utah and northwestern Oregon. According to the National Interagency Fire Center, over 100 large wildfires were burning across the U.S. on August 13. These were concentrated in the West, especially northern California to southwestern Oregon, Arizona, western Colorado to northeast Utah, northern Oregon to central Washington, and western Montana into adjacent Idaho. According to August 12 USDA reports, 65% of the pasture and rangeland in Washington was in poor to very poor condition, and 90% of the topsoil was short or very short of moisture; 27% of the pasture and rangeland in Idaho was in poor to very poor condition, and 72% of the topsoil and 67% of the subsoil was short or very short of moisture; 63% of the pasture and rangeland in Montana was in poor to very poor condition, and 90% of the topsoil and 56% of the subsoil was short or very short of moisture; 61% of the pasture and rangeland in New Mexico was in poor to very poor condition, and 74% of the topsoil and 77% of the subsoil was short or very short of moisture; 47% of the pasture and rangeland in Utah was in poor to very poor condition, and 68% of the topsoil was short or very short of moisture; 30% of the pasture and rangeland in Nevada was in poor to very poor condition, and 65% of the topsoil and 60% of the subsoil was short or very short of moisture; 35% of the pasture and rangeland in California was in poor to very poor condition, and 70% of the topsoil and 70% of the subsoil was short or very short of moisture. According to USDA reports, last week 98% of the pasture and rangeland in Arizona was in poor to very poor condition. The rains this week improved pastures and rangeland to 88% poor to very poor.
Since the Tuesday morning cutoff time of this week’s USDM, heavy rain has fallen across some of the drought areas in Missouri, with additional rain over Kansas; rain was moving across Nebraska and South Dakota in the Plains and into the Ohio Valley and across parts of the Northeast; and monsoon precipitation had overspread parts of the Southwest. For August 16-20, dry weather will continue across the Far West and much of Texas; monsoon showers will bring a few tenths of an inch to locally over an inch of rain to the Southwest; and fronts and low pressure systems will bring over an inch of rain to a large area stretching from the central and northern Plains, across the Midwest, to most of the Southeast and Northeast, with up to half an inch to an inch across the Rockies to High Plains. Less than an inch of rain is expected for parts of the Great Lakes, Florida, and the Mid-Atlantic. Temperatures are expected to be warmer than normal across the West and cooler than normal in the Great Plains, with near-normal temperatures east of the Mississippi River. For August 21-29, odds favor below-normal precipitation across the Pacific Northwest to northern Plains, and above-normal precipitation for the Southwest to Southeast, Ohio Valley to Great Lakes, Northeast, and most of Alaska. There is a higher probability for warmer-than-normal temperatures in the West, along the Gulf of Mexico coast, along the East Coast, and in much of Alaska, while cooler-than-normal temperatures are favored to dominate the Plains to Midwest.
Richard Heim, NOAA, NCEI
Richard Heim, NOAA, NCEI