Saturday, July 28, 2012

Severe Weather Threat May Accompany Early August Disturbance

The 12z ECMWF is projecting a disturbance to move southward and slip into the Upper Midwest in early August, similar to that of the system that produced several damaging bowing segments over the Upper Midwest, Great Lakes and Northeast over the past several days.

What happened then and is forecast to happen in early August have very similar features, as seen below in this chart of the weather pattern on July 23.

On July 23, there was a low pressure system in the Upper Midwest with trailing cold front, with a ridge of high pressure extended from the Southeast out into the Plains. If we compare this map to the ECMWF forecast, it does become apparent that these systems are very similar. A key difference in any possible resulting thunderstorm track is the lack of a ridge in the Southeast. One was observed on July 23, which was the day of the derecho in the Ohio Valley. However, now, with the lack of a ridge, we could see the progression of possible storms more into the Ohio Valley. Also of potential is that the system could move east and the storms would deflect into the Northeast. Time will tell, and the models should align soon.


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