According to the May 16, 2017, U.S. Drought Monitor, moderate to extreme drought covers 5.6% of the contiguous United States, a slight increase from last week’s 5.2%. Areas in extreme drought also increased slightly from around 0.3% last week to 0.4%. Exceptional drought, the worst category, continued to remain absent from the country for the 17th consecutive week.
The upper-level circulation during this U.S. Drought Monitor week saw a continuation of what is called a “highly meridional flow.” A series of strong closed lows slowly moved across North America, with several of them favoring the southwestern contiguous United States. Warm dry air masses were forced northward beneath upper-level ridges in between these closed lows, especially over the central and southeastern Lower 48. This weather pattern resulted in above-normal average temperatures from the Northern Plains to Southeast and below-normal temperatures along the West Coast and Northeast.
Above-normal precipitation occurred in areas where the closed lows fed Pacific and Gulf of Mexico moisture into showers and powerful thunderstorms, especially along the Pacific Northwest Coast, Southwest to Central Plains, and coastal Northeast. But, more importantly, the slow movement of these closed lows, and their associated surface lows and cold fronts, triggered bouts of severe weather, especially in the Plains to Midwest. Drier-than-normal weather occurred beneath the upper-level ridges and in areas missed by the storms.
In addition to Drought.gov, you can find further information on the current drought as well as on this week’s Drought Monitor update at the National Drought Mitigation Center. See their recent news releases.
The most recent U.S. Drought Outlook is available from NOAA’s Climate Prediction Center and the U.S. Department of Agriculture provides information about the drought’s influence on crops and livestock.