Friday, July 12, 2013

Record Rainfall Drenches Dulles;
Update: Rain Ransacks Roanoke Record

Images (click to enlarge): Washington, DC regional radar, 12:49 am EDT, July 12, 2013, from The Weather Channel; 24-hour precipitation ending 8 am EDT, July 13, 2013, for Washington region, from National Weather Service

2 PM EDT Update: The 3.88" a day earlier (July 10) at Roanoke smashed the daily record of 2.67" in 1931. It was also a new all-time July daily record in a climate history which began over a century ago in 1912. Daily amounts of 3" or more had been observed only twice before in July at Roanoke.

The 1.84" at Richmond also broke a July 10 record of 1.36" set just last year.

To the north, the 2.44" at Pittsburgh beat the daily record of 1.81" in 1958.

10 AM EDT Update: The preliminary July 11 record daily total rainfall for Dulles is 3.71". The 24-hour total ending at 8 am is 4.49", with some light rain continuing.

2 AM EDT Update: Dulles has added 0.22" from lighter thundershowers in the past hour for a storm total so far of 3.79". The reported month-to-date total is now 370% of normal.

Original Post:
Persistent thunderstorms Thursday evening have produced record rainfall in the Virginia suburbs of Washington, DC. At Dulles Airport, the unofficial total of 3.61" through midnight (standard time) was over 3 times the old record for July 11 of 1.12" in 1977. Climate records at Dulles date back only a half-century to 1962, but this was also enough to beat the all-time July daily record of 3.50" on July 27, 1994.

The official climate record for Washington, DC, which began in 1871, shows that July daily rainfalls of 4" or more have occurred on at least 3 occasions:
4.69", July 9, 1970
4.35", July 22, 1969
4.25", July 30, 1878

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