Wednesday, July 14, 2010

Midsummer Precipitation Review: Who Ya Gonna Call? Drought Busters!

For more posts on Washington, DC temperature and precipitation, see:
Washington DC Weather Records

July 15 Update: As expected, the new Drought Monitor report including data through Tuesday shows little change from last week.
  • The Virginia total drought area remains at 85.9%, with the Moderate Drought portion increasing slightly to 37.4%.
  • The Maryland total drought area declines to 85.6%, with Moderate Drought down a little to 60.5%.
Original post:
Just when we were getting the "d" word on the brain, the chefs down at Momma Nature's Weather Grill decided to revise the menu. The Washington-Baltimore area has been in the sweet spot for a series of showers and thunderstorms over the last several days. In fact, 5 out of the last 6 days have had measurable rain, and 2 of those had over 1", with over 2" in the 24 hours ending this morning. This brings the Washington July total to 3.77" so far, over 3 times the amount in last year's near-record dry July and a few percent above the normal amount for all of July.

Although lawns and gardens are looking much happier in the short run, the longer-term deficit remains. Five of the 6 months so far this year have been below average. Although March was barely below, February was barely above, so the year-to-date deficit is still 3.42". Furthermore, the heaviest recent rain has been concentrated along the I-95 corridor, so some outlying areas in Maryland and Virginia are still running dry, particularly Southern Maryland, the Eastern Shore and the Northern Neck of Virginia. Even as close as Dulles Airport, the July total is less than half of the Washington National amount. This week's drought report to be issued tomorrow won't include the latest downpours, but conditions should be improved across much of the immediate area.

Here are the regional July precipitation totals to date and monthly/seasonal (since June 1)/yearly departures from average:
Washington National  3.77"/+2.14"/+0.88"/-3.42"
Washington Dulles 1.79"/+0.11"/-2.67"/-2.77"
Baltimore BWI 2.83"/+1.12"/-0.76"/-0.46"
Baltimore Downtown 4.06"/NA/NA/NA
Images (click to enlarge): July 2010 precipitation percentage of normal through 8 am EDT, July 14, from National Weather Service; Washington, DC 2009-10 monthly precipitation and departures from average, CapitalClimate charts from National Weather Service data

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