A waterspout or tornado over water was captured on video looming over Lake Michigan near Marquette University off the Wisconsin shoreline of Lake Michigan Saturday.
Waterspouts were reported over Lake Michigan near Chicago and Milwaukee between 10:00 a.m. and noon Saturday, September 24, 2011.
Warm lake water and cool air aloft creates a gradient of about 30°F, which is favorable for the formation of waterspouts. The waterspouts dissipated as they headed west toward land.
The weather circumstances included a cut-off low just east of Chicago that caused a prolonged period of unseasonably cool weather with convective thunderstorms moving in a counterclockwise direction (from southeast to northwest) in the region. When an upper level high or low pressure system becomes stuck in place due to a lack of steering currents, it is known as being “cut off”.
A cut-off high usually leads to dry, warm weather as the air beneath it is compressed and warmed. A cut-off low usually leads to rainy, cooler weather.
Clouds forming well inland west of Palatine, Illinois late Saturday about noon.
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