Jun 30, 2011
The cities of Racine, Kenosha, Winthrop Harbor, Zion down the lakeshore communities to Chicago, Illinois experienced a unusual severe thunderstorm episode that produced damaging winds and large hail Thursday evening. Many trees were uprooted, powerpoles snapped resulting in numerous power outages along the path of the storm.
Numerous thunderstorms developed over Lake Michigan throughout the daylight hours producing heavy rain for mariners. The severe weather threat was low for most areas as the storm would continue to move southeast out over the water. During the late afternoon some of the storms became more supercellular in nature causing their forward motion to deviate towards the right. This usually indicates mid level rotation within the storm. As a consequence the storms began moving more south-southwesterly towards the Wisconsin/Illinois lakeshore counties.
One particular storm came close to the Lake Michigan shoreline producing wind damage across Racine and Kenosha Counties. The storm itself stayed out over Lake Michigan yet the rear flank downdraft sent very strong outflow winds around the backside of the storm. These winds traveled on the open waters of Lake Michigan where there is less friction (no trees or buildings) for the surging winds to slow down. The intensity of the storm and the lack of land friction caused the winds to be very strong along the lake shore into Lake County, Illinois. The storm had an additional component producing large hail as it started to make land north of Chicago, Illinois. Reports as high as baseballs were received causing some damage to vehicles.
Racine County Storm Photos
Interestingly these storms were caused by advancing warm air moving into Wisconsin and Illinois better know as warm air advection. A strong low level jet, warm frontal boundary, high instability and moisture fueled these storms as they were rounding the base of a ridge of high pressure centered across the central U.S.
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