According to the December 29, 2020, U.S. Drought Monitor, moderate to exceptional drought covers 41.0% of the United States including Puerto Rico, a decreasefrom last week’s 41.5%. The worst drought categories (extreme to exceptional drought) are the same as last week: 18.6%.
The overall circulation pattern this week consisted of several strong Pacific weather systems rapidly moving across the contiguous United States through an overarching longwave upper-level ridge. The ridge inhibited precipitation and worked to keep temperatures warmer than normal. The Pacific weather systems, which consisted of shortwave troughs and closed lows, brought clouds, areas of precipitation, and cooler-than-normal weather.
The weather systems weakened as they crossed the West but were reinvigorated when they reached the eastern contiguous United States. Their fronts and surface lows tapped Gulf of Mexico moisture to spread above-normal precipitation across the central Plains to Great Lakes, and they tapped Gulf and Atlantic moisture to bring widespread precipitation to the central Gulf Coast to Northeast. They also spread Pacific moisture along the immediate West Coast and over parts of the Rocky Mountains, but even then the precipitation amounts were still generally below normal.
The rest of the West, Plains, and Midwest, as well as most of Florida, were drier than normal this week. Drought or abnormal dryness expanded in parts of the Plains, Midwest, and Lower Mississippi Valley, but contracted in parts of the Southeast and much of the Northeast. Drought contraction was more than expansion, so the overall U.S. drought footprint decreased this week.
Abnormal dryness and drought are currently affecting over 125 million people across the United States including Puerto Rico—about 40.4% of the population.
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.