Mid Atlantic Precipitation Update

See here for more Washington, DC weather records.

The major storm moving through the central part of the U.S. brought record-breaking rain for December 9 to the Washington/Baltimore metro area. The 1.29" which fell at Washington National exceeded the record of 1.05" set in 1931, although that was previously the lowest daily record for December. Baltimore (BWI) also broke its record with 1.41", well above the old record of 1.08" in 1991. Washington Dulles, on the other hand, with a much shorter period of record, had 0.93", which failed to break the 1973 record of 1.12".

In the first 9 days of the month, Washington National is now within 0.01" of the average total for all of December. This is almost 2.5 times the average December amount to date. At 4.43", the November rainfall was just under 50% above average. April, May, June, and October, the other above-average months this year, have all been at least 50% above. February and July were over 50% below average. If current trends continue, December will be the seventh month in 2009 which is at least 50% above or below average.

Daily, monthly, and year-to-date amounts are:

Washington National 1.29"/3.04"/43.15"
Washington Dulles   0.93"/2.49"/45.13"
Baltimore (BWI)     1.41"/3.68"/51.19"  

Other daily records set in the Mid Atlantic region (old record in parentheses):

Wallops Island VA 2.93" (0.93", 1995)
Martinsburg WV    1.15" (0.98", 1978)
Newark NJ         1.96" (1.66", 1978)
Atlantic City NJ  2.51" (1.31", 1986)
Islip NY          1.74" (1.07", 1995)
Reading PA        1.16" (1.12", 1978)
Philadelphia PA   2.13" (1.91", 1978)
Pittsburgh PA     0.85" (0.71", 1878)
Wilmington DE     2.28" (1.55", 1978) 
Georgetown DE     1.93" (1.38", 1963) 

Images (click to enlarge):
- 24-hour precipitation ending 7 am December 9, from National Weather Service
- Washington DC 2008-2009 monthly precipitation amounts and percentages above or below average, CapitalClimate charts from NWS data