Source: droughtmonitor.unl.edu
Map released: Sept. 19, 2019 | Data valid: Sept. 17, 2019
This week’s summary: Rapidly intensifying “flash drought” — attributed in part to extreme late-summer heat — continued to afflict many areas from the lower Midwest and Mid-Atlantic States to the Gulf Coast. Likewise, an abysmal Southwestern monsoon (to-date) led to increasing drought intensity and coverage in Arizona, while short-term drought persisted across the Hawaiian Islands. Conversely, moderate to heavy rain eased or alleviated dryness and drought from the Great Lakes into the Northwest as well as in southwestern Alaska and southern Puerto Rico.
South: Intense late-summer heat and acute short-term dryness led to a sharp increase in drought intensity and coverage across central portions of the region. Excessive heat (95-102°F) and pronounced short-term rainfall deficits (30-day rainfall totaling locally less than 10 percent of normal) heightened evapotranspiration rates and soil moisture losses, resulting in quickly escalating drought impacts (often referred to as a “flash drought”.) It should be noted that “flash drought” often occurs more quickly (in terms of impacts) than the data indicates. In terms of temperatures, Wednesday, September 18th marked the 18th consecutive day of 90-degree heat at Little Rock, Arkansas (the long term historical total-September average is 9 days); September 18th also marked the 7th day with 100-degree readings at Meridian, Mississippi (only one other year—1980—had this many, and only 7 other years total had 3 or more (records dating back to 1889)). For this weeks’ analysis, the expansion of D0 (Abnormal Dryness) as well as Moderate (D1) to Extreme Drought (D3) was driven by guidance from local experts, impact reports from observers, as well as temperature- and rainfall-driven data products which focused on the past 30 to 60 days. Increases in drought were most pronounced from central and northeastern Texas into the central and northern Mississippi Delta, where 60-day rainfall has totaled a meager 25 percent of normal or less. State-wide average topsoil moisture was rated more than 70 percent short to very short (according to USDA-NASS) as of September 15 in the Mississippi Delta States, and 83 percent poor to very poor in Texas (tied for second highest in the nation with Virginia, only 2 percentage points behind California’s 85 percent). Despite the generally dry, hot weather pattern, heavy showers and thunderstorms (2-4 inches) provided highly localized drought relief across southeastern and north-central Texas as well as western Oklahoma. After the end of the monitoring period (12z Tuesday), heavy showers associated with the remnants of Tropical Storm Imelda were bringing rain to southeastern Texas; the impacts of this rainfall will be incorporated in next week’s U.S. Drought Monitor.
Looking Ahead: An active weather pattern will foster periods of moderate to heavy rainfall from the southern Plains into the Midwest, while intermittent rain and mountain snow linger from the Pacific Northwest into the northern Rockies. Meanwhile, moisture associated with the remnants of Tropical Storm Imelda will fuel locally heavy showers in southeastern Texas and the western Delta. Some late-season monsoon showers are also possible in the Four Corners Region, though the heaviest rain may stay east of the region. Despite the stormy weather pattern, little—if any—rain is expected across the Southeast, with only light showers in the offing farther north in the Mid-Atlantic and Northeastern States. The NWS 6- to 10-day outlook for September 24–29 calls for above-normal temperatures along the central California Coast and from the Rockies to the East Coast; cooler-than-normal weather will be confined to the Northwest and lower Southwest. Near- to above-normal precipitation across much of the nation will contrast with drier-than-normal conditions from the Southeast into the Mid-Atlantic States.
This week’s summary: Rapidly intensifying “flash drought” — attributed in part to extreme late-summer heat — continued to afflict many areas from the lower Midwest and Mid-Atlantic States to the Gulf Coast. Likewise, an abysmal Southwestern monsoon (to-date) led to increasing drought intensity and coverage in Arizona, while short-term drought persisted across the Hawaiian Islands. Conversely, moderate to heavy rain eased or alleviated dryness and drought from the Great Lakes into the Northwest as well as in southwestern Alaska and southern Puerto Rico.
South: Intense late-summer heat and acute short-term dryness led to a sharp increase in drought intensity and coverage across central portions of the region. Excessive heat (95-102°F) and pronounced short-term rainfall deficits (30-day rainfall totaling locally less than 10 percent of normal) heightened evapotranspiration rates and soil moisture losses, resulting in quickly escalating drought impacts (often referred to as a “flash drought”.) It should be noted that “flash drought” often occurs more quickly (in terms of impacts) than the data indicates. In terms of temperatures, Wednesday, September 18th marked the 18th consecutive day of 90-degree heat at Little Rock, Arkansas (the long term historical total-September average is 9 days); September 18th also marked the 7th day with 100-degree readings at Meridian, Mississippi (only one other year—1980—had this many, and only 7 other years total had 3 or more (records dating back to 1889)). For this weeks’ analysis, the expansion of D0 (Abnormal Dryness) as well as Moderate (D1) to Extreme Drought (D3) was driven by guidance from local experts, impact reports from observers, as well as temperature- and rainfall-driven data products which focused on the past 30 to 60 days. Increases in drought were most pronounced from central and northeastern Texas into the central and northern Mississippi Delta, where 60-day rainfall has totaled a meager 25 percent of normal or less. State-wide average topsoil moisture was rated more than 70 percent short to very short (according to USDA-NASS) as of September 15 in the Mississippi Delta States, and 83 percent poor to very poor in Texas (tied for second highest in the nation with Virginia, only 2 percentage points behind California’s 85 percent). Despite the generally dry, hot weather pattern, heavy showers and thunderstorms (2-4 inches) provided highly localized drought relief across southeastern and north-central Texas as well as western Oklahoma. After the end of the monitoring period (12z Tuesday), heavy showers associated with the remnants of Tropical Storm Imelda were bringing rain to southeastern Texas; the impacts of this rainfall will be incorporated in next week’s U.S. Drought Monitor.
Looking Ahead: An active weather pattern will foster periods of moderate to heavy rainfall from the southern Plains into the Midwest, while intermittent rain and mountain snow linger from the Pacific Northwest into the northern Rockies. Meanwhile, moisture associated with the remnants of Tropical Storm Imelda will fuel locally heavy showers in southeastern Texas and the western Delta. Some late-season monsoon showers are also possible in the Four Corners Region, though the heaviest rain may stay east of the region. Despite the stormy weather pattern, little—if any—rain is expected across the Southeast, with only light showers in the offing farther north in the Mid-Atlantic and Northeastern States. The NWS 6- to 10-day outlook for September 24–29 calls for above-normal temperatures along the central California Coast and from the Rockies to the East Coast; cooler-than-normal weather will be confined to the Northwest and lower Southwest. Near- to above-normal precipitation across much of the nation will contrast with drier-than-normal conditions from the Southeast into the Mid-Atlantic States.