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Pulse Severe Thunderstorms of May 31st, 2006

Summary

Much like the previous day, the afternoon of May 31st, 2006 brought abnormally hot temperatures in the mid to upper 80s to Central PA. The hot weather combined with increasing low level moisture and the rugged terrain of Central PA to produce a second day of tall and damaging pulse thunderstorms. A PULSE thunderstorm is one that typically grows up due to a point source of heating and lift, and collapses when it moves away from that source of lift. Pulse thunderstorms may pulse up and collapse many times, and may move very slowly. This means they are threats for flash flooding as well as hail and, more rarely, wind damage. If a pulse thunderstorm makes damaging wind gusts, it is usually because the storm has so much water held aloft and the cooling from the evaporation in the mid layers of the atmosphere is so great that the cooled air rushes down to the ground with great velocity.
 
That was the case on this May 31st as well, which is a banner day for severe weather in Central PA. May 31st is the anniversary of the Great Johnstown Flood of 1889, and two devastating tornado outbreaks in 1985 and 1998. A handful of storms made large hail, and flash flooding, including mudslides this May 31st. The mudslides were most likely caused by the second day of heavy rain for many local spots in the higher elevations of PA, and may have been made worse by wildfires that burned up rural areas earlier during the very dry spring of 2006.

Preliminary Damage Reports in Text format

Images

Reflectivity from 2037z (437pm EDT) with terrain- and heat-induced pulse thunderstorm over Somerset County
Reflectivity from 2037z (437pm EDT) with terrain- and heat-induced pulse thunderstorm over Somerset County. This storm produced large hail and torrential rain.

Reflectivity Cross Section of the storm over Somerset County that made very large hail and heavy rain.
Reflectivity Cross Section of the storm over Somerset County that made very large hail and heavy rain. Note the high (red) reflectivities held aloft up to 40 thousand feet!


 
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Page Last Modified: 04 June 2006 19:05:33 UTC
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