Damaging hail storm impacts NE WI 9 years ago today

May 12th, 2009 at 5:59 pm by under Uncategorized

One of the most damaging thunderstorms in Wisconsin’s history struck the area 9 years ago today. There was a weak tornado from this thunderstorm that briefly touched down just outside of St. Nazianz, but no damage was reported. The damage, however, from this storm was as a result of large hail and straight-line winds. It caused $122 million dollars in damage. Just to give you some perspective, the costliest tornado in Wisconsin’s history caused $84 million (adjusted for inflation) worth of damage. That was the F5 tornado that struck Barneveld in 1984.

You might be wondering how this could happen? But when you put the event in perspective, it makes sense that it was more costly than the Barneveld tornado.  Hail damaged more than 1,000 homes in Omro and Chilton. In addition, most homes in a mobile home park in St. Nazianz were overturned or knocked off their foundation by the straight-line winds.

Most severe weather in this part of the nation occurs in the afternoon and evening, when instability is highest, but this storm struck before noon on May 12th of 2000. The supercell thunderstorm developed to the north of a warm front which was located along the Wisconsin/Illinois border.

Below is a radar image taken at 10:30 am. At this time the storm was producing large hail over western and central Waushara counties. The highest reflectivity represents the area where the large hail fell. Hail the size of baseballs was reported in Red Granite.

The line from A to B represent a cross-section shown below.


As you can see the top of the storm reached nearly 60,000 feet in the atmosphere.

The supercell didn’t lose strength as it continued to advance through Winnebago, Calumet and Manitowoc counties. Straight-line winds reached 80 mph in Chilton, with speeds of 100 mph in St. Nazianz (EF1 tornadoes have estimated wind speeds around 100 mph) In both locations there were also reports of hail larger than the size of a golf ball. The wind-driven hail shredded west facing sides of homes and businesses.

This storm was so significant that its effects were even visible from space. Below is a false color satellite image taken one week after the storms passed. The green areas represent vegetation while the pink/brown color represents urban areas or bare soil. It is easy to identify pink/brown line from Lake Winnebago to Manitowoc, that is the same path the storm took.

Until Next Time,
Meteorologist Andrew Thut

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