Tools used in the U.S. Monthly Drought Outlook (MDO) included the updated Climate Prediction Center (CPC) temperature and precipitation outlooks for October, various short- and medium-range forecasts and models such as the 7-day quantitative precipitation forecast (QPF) totals from the Weather Prediction Center (WPC), the 6-10 day and 8-14 day CPC extended-range forecasts (ERFs), Week 3-4 outlooks, CFSv2 monthly forecasts of temperature and precipitation, the 384-hour total precipitation forecasts from several runs of the GFS, climatology for October, and recent precipitation. The September 26 U.S. Drought Monitor (USDM) was used to identify existing drought areas (D1 or drier) in the MDO. For consistency, MDO regional write-ups will be based upon the 7 regions in the U.S. Drought Monitor summary.
During September, temperatures were below normal across Montana, northern Wyoming, Utah, southeastern California, and southwestern Arizona. The cooler-than-normal temperatures across Montana and northern Wyoming were due in large part to widespread cloudiness and precipitation, and a persistent mid-level trough especially during the second half of the month. Percent of Normal Precipitation (PNP) ranged from 110 to 400 percent of normal, especially in eastern Idaho, and much of Montana and Wyoming. For remaining areas of the West, which encompass about one-half of that region, above normal temperatures prevailed, along with relatively dry conditions. WPC's Week-1 precipitation forecast indicates significant precipitation (1-3 inches) across the Cascades, the Rockies, and most of Montana. CPC's Week-2 precipitation outlook continues the wet pattern across the Rockies. The experimental Week 3-4 precipitation outlook favors wetter-than-usual conditions across the Northwest, and Equal Chances over most of the remainder of the West. The drought outlook for October 2017 favors drought removal over western Washington, which is consistent with early-autumn climatology, drought improvement over northeastern Montana due to anticipated heavy precipitation just in the first week of October, and drought persistence and/or intensification for all other areas of the West.
Forecast confidence for the Western region is moderate to high.
Temperatures in September were warmer than normal across most of the High Plains region, with the exception of the western Dakotas, which reported below normal temperatures. Two bands of heavy precipitation (ranging up to 2-4 inches above normal) were observed; one over the western Dakotas, and the other from the central High Plains to the eastern Dakotas. During Week-1, heavy precipitation (2-4 inches) is predicted by WPC across central and eastern Nebraska, and extreme southeastern South Dakota. According to CPC, there are elevated odds for above-normal precipitation across this entire area during Week-2. CPC's experimental Week 3-4 precipitation outlook favors EC across most of the Dakotas and the Nebraska Panhandle, and below-normal elsewhere. Most drought in this region is expected to persist and/or intensify, with only two exceptions. The first exception is over northwestern North Dakota, where improvement is anticipated, and the second exception is over far southeastern South Dakota, where above-normal precipitation is forecast during the first two weeks of the month.
Forecast confidence for the High Plains is moderate.
Temperatures across approximately the northwestern half of the South were above normal in September, and below normal over the southeastern half of the region. The latter area was influenced by Hurricane Harvey at the end of August, with unprecedented rainfall and catastrophic flooding in portions of east Texas. Over the ensuing 7-day period, rainfall is expected to be moderate (0.5-2.0 inches) near the Gulf Coast, the Texas Panhandle, and much of Oklahoma. Most of this area is expected to have near normal rainfall during Week-2, and below normal rainfall during the Week 3-4 period. Prospects for drought removal are improved across most of Texas and Oklahoma, but not as promising for the Arklatex region, where drought may persist. In addition, throughout the month of October, precipitation is favored to be primarily below normal (except near-normal during Week-2) across the Arklatex and Arkansas, which is conducive for drought development.
Forecast confidence for the South is moderate.
Warm, dry conditions prevailed across the Midwest during September, except in Kentucky where temperatures verified slightly cooler than average thanks to cloud cover and significant rain from Hurricane Irma two weeks ago. During the past 30-days, 2-4 inch precipitation deficits mounted primarily in Missouri, Illinois, and Lower Michigan. A swath of heavy rain (2-4 inches) is forecast to set up in the Week-1 time frame over much of northwestern Iowa, Minnesota, and northwestern Wisconsin, but unfortunately most of this heavy rain is expected to fall in areas that are currently not in drought. Therefore, drought persistence and/or intensification, and new drought development, is anticipated for most of the Midwest region in October.
Forecast confidence for the Midwest region is moderate to high.
At the present time, there is no drought in the Southeast, thanks primarily to recent rainfall associated with Hurricane Irma. Areas that missed out on this precipitation, such as Virginia and (parts of) North Carolina, are experiencing increased dryness (D0 on the U.S. Drought Monitor). Deficits of 1-4 inches during the last 30-days have been reported by the Advanced Hydrologic Prediction Service (AHPS), with some of the largest deficits noted over southeastern Virginia. Precipitation expected during the next 30-days does not appear to be anywhere near enough to offset pending drought development in this area. October is a climatologically drier month for Virginia as well.
Forecast confidence for the Southeast is moderate to high.
Most of the Northeast is currently free of drought and dryness, though there is one area of moderate drought (D1 on the U.S. Drought Monitor) across eastern Maine, and a few widely scattered areas of dryness (D0). One of these dryness areas includes most of the remainder of the New England coast, where deficits of 1-3 inches were generally noted in the past 30-days. The exception is Cape Cod, where precipitation surpluses of 1-3 inches were observed in the same period (about 4-5 inches in Nantucket). With below to near normal precipitation anticipated for the next 30-days, there is no reason why drought development isn't the most likely scenario for approximately the southern half of the Northeast region, and most of the New England coast.
Forecast confidence for the Northeast is moderate.
Warm and dry conditions continue across the Hawaiian archipelago. The state's rainy season is still several months away, and there is no compelling reason at this time to anticipate any significant mitigation of drought. Therefore, drought persistence and/or intensification is deemed the best choice.
Forecast confidence for Hawaii is moderate to high.
Forecaster: Anthony Artusa
Next Monthly Drought Outlook issued: October 31, 2017 at 3pm EDT