Saturday, June 30, 2012

Eastern US derecho

A tremendously destructive derecho raced from northern Illinois all the way to the east coast yesterday afternoon and evening. This windstorm left thousands without power and produced numerous surface wind gusts that far exceeded synoptic scale winds aloft at any level. The graphic above shows the severe storm reports from SPC - note that over a thousand severe reports were logged. It is interesting to note the lack of reports from West Virginia - apparently this reflects problems with the reporting network and not a real lack of strong winds there.

Above is a water vapor image from 8 pm MST (11 pm EDT) yesterday. The large derecho system was approaching the east coast, with a smaller trailing system over northern Illinois. A similar appearing, large MCS was also occurring over northern Sonora. The 00 UTC evening sounding from Sterling, Virginia, (below) taken ahead of the derecho, exhibits tremendous CAPE values and a nearly linear hodograph - both characteristic of environments that produce derechoes.

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