Storm Relative Velocity Image Southern Wisconsin Severe Weather Outbreak

May 28, 1998

Storm Relative Velocity Image


...Here is a summary of the severe weather outbreak on May 28, 1998...

Through much of the day on May 28th, a quasi-stationary front was draped from Southeastern South Dakota through Southern Wisconsin. This boundary was the focus for showers and thunderstorms later in the afternoon and evening hours. The Storm Prediction Center had indicated a Slight Risk of severe thunderstorms across Southern Wisconsin and much of the Upper Midwest near or south of the frontal boundary. By the afternoon hours a very unstable airmass had set up to the south of the front and isolated thunderstorms were beginning to develop across portions of Southeast South Dakota and Northwest Iowa. These thunderstorms acted on the instability, and strong vertical wind shear caused by a westerly jet stream aloft, to quickly become severe across portions of Northern Iowa.

The thunderstorms organized in Northern Iowa through the afternoon hours and by early evening they were finally approaching the Mississippi River and Southwest Wisconsin. At 6:05 pm the Storm Prediction Center issued a Severe Thunderstorm Watch for portions of Southern Wisconsin, Northern Illinois and extreme Eastern Iowa to be valid until 1:00 am. The watch included the threat of large hail to 2 inches in diameter and damaging winds to 80 mph. A cluster of thunderstorms was expected to push through the watch area with damaging downburst winds.

Reflectivity images for:

730 PM / 800 PM / 830 PM / 900 PM / 930 PM / Click for animated loop

Storm Relative Velocity images for:

730 PM / 800 PM / 830 PM / 900 PM / Click for animated loop

By 7:30 pm the strongest thunderstorms were located across Western Wisconsin, or extending along a line from Monroe County through Grant County and close to Dubuque, Iowa. Also, a powerful thunderstorm was nearly stationary over Western Lafayette County and radar estimates suggested that this storm produced 3 to 4 inches of rainfall in under an hour. The line of thunderstorms progressed and eventually the southern extent merged with the slow moving thunderstorm cells in Lafayette County.

Between 8:00 pm and 9:00 pm the line of severe thunderstorms began acting erratically, but still produced severe wind gusts and isolated severe hail along its track. At 8:00 pm the line of thunderstorms split into two lines. One extended from near Mauston in Juneau County to Plain in Sauk County and the other from near Dodgeville in Iowa County to Galena, Illinois. The lines stayed fairly split as they began to bow out although some brief redevelopment was noted in between the segments in Northern Dane County around 8:15 pm. The two bow echoes moved east at about 35 mph across South-Central Wisconsin producing severe wind damage through 9:00 pm. Columbia County was probably hardest hit in this timeframe with golfball size hail in Cambria and 1300 electrical customers losing power due to high winds.

Around 9:00 pm the bow echoes were beginning to lose strength, but rapid new development occurred near where the Dane, Rock and Green County borders all intersect or just southwest of Stoughton. This line quickly became severe and went on to produce damaging winds across much of Southeast Wisconsin near or south of Interstate-94. The northern extent of the line, at that time across Eastern Green Lake County, were rapidly losing much of their strength although several severe wind reports were received in Western Fond du Lac and Northern Dodge Counties.

Southeast Wisconsin received the brunt of storm damage due to high winds. Roof damage was noted in Jefferson to several homes, and several farms in Jefferson County also received damage. Lighting hit four homes in Waukesha County and knocked out power to 3000 customers while a 70 mph wind gust was recorded at Waukesha County airport. A boat on Lake Geneva was lifted out of its cradle and damaged. Racine County reported pole barn damage and boat damage as well as two and a half feet of water standing on Highway 20. In all, 26 severe wind reports were received in the WFO Milwaukee/Sullivan County Warning Area along with two severe hail reports and one funnel cloud report.

Please direct any questions or comments to our Warning Coordination Meteorologist at the following email address: Rusty.Kapela@noaa.gov

A sincere thanks is extended to the spotters for their willingness to share their photographs.


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