A cold front interacting with a very warm humid air mass resulted in explosive growth of thunderstorms during the evening hours of Aug 2, 2011. The day had been very hot and humid with the temperature topping out at 95° and the dew point hovering around 80°. A band of severe storms moved out of Wisconsin and affected the far northeast counties in Illinois…north of Chicago. At the time I thought the show was over. Later however storms developed rapidly over portions of the Rock river valley and began moving southeast and eventually made it to Grundy county. Here is a list of storm reports for Grundy county as of 1PM 8/23/11 courtesy NOAA/NWS Chicago:
1001 PM TSTM WND DMG COAL CITY 41.29N 88.28W
08/02/2011 GRUNDY IL PUBLIC
TREE DOWN ON HOUSE.
1001 PM TSTM WND DMG COAL CITY 41.29N 88.28W
08/02/2011 GRUNDY IL PUBLIC
TREE BLOCKING KANKAKEE ST. TRANSFORMER DOWN.
1001 PM TSTM WND GST 2 W COAL CITY 41.29N 88.32W
08/02/2011 M64.00 MPH GRUNDY IL MESONET
1008 PM TSTM WND GST SSE MINOOKA 41.45N 88.26W
08/02/2011 M57.00 MPH GRUNDY IL MESONET
My Boltek lightning detector definitely got a workout. At the time it detected a peak lightning rate of 2094 strikes per minute. Most were in cloud but there were many close cloud to ground strokes as well. The following images show the lightning display and radar image around that time. Note: this detector is not nearly as accurate as those used in professional detection networks (costing much, much more).
Aug 2, 2011 Radar Image (severe thunderstorm warnings denoted by red polygons)
August 2, 2011 Lightning Display