Summary

The afternoon of May 30th, 2006 brought near record high temperatures in the upper 80s to lower 90s to Central PA. This unusually hot weather combined with increasing low level moisture to produce some very 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.

Preliminary Damage Reports in Text format

Images

Composite Reflectivity from 2258z (658pm EDT) with terrain- and heat-induced pulse thunderstorms over Central PA. Note the storm east of Sunbury, which produced large hail near Knobel's Amusement Park in Columbia County, and the storm over Somerset County.

Visible Satellite Picture from 2300z with past-15-minute-lightning overlaid. Note the shadows on the overshooting tops that show up nicely with the late-day sun angle. An Overshooting Top is a sign of a very strong updraft.