1998 Wisconsin Derecho

Southern and central Wisconsin experienced a memorable, widespread damaging wind event during the late evening hours on Saturday, May 30th into the early morning hours of Sunday, May 31, 1998. The damage totaled about $60 million to property and $1.82 million to crops. Three people were killed during or shortly after the event: 1 directly and 2 indirectly. At least 37 people were injured. Hundreds of structures such as homes, businesses, and farm buildings were damaged; thousands of trees were toppled or split, and hundreds of power lines were pushed over.

Meteorologically, a line of severe thunderstorms, referred to as a squall line, raced east at about 50 mph across the southern two-thirds of the Badger state. Embedded in the squall line were several intense macrobursts and microbursts that resulted in concentrated swaths of structural or tree damage. Measured wind gusts exceeded minimal hurricane-force speeds of 74 mph in many locations, and in several spots exceeded 100 mph. The maximum measured wind gust was 128 mph northeast of Watertown in southern Dodge county. In addition, seven tornadoes touched down, scattered from west central to east central Wisconsin, and there were several large hail occurrences.

Information on the path and storm path image is from the " Southern Great Lakes Derecho of 1998"  SPC writeup

The image to the right shows the path of damage from the complex for thunderstorms that developed and raced across the midwest from May 30-31, 1998. The main event started in South Dakota during the afternoon of May 30th, 1998. Supercell thunderstorms developed during the afternoon and some produced tornadoes, one violent tornado to note was the  Spencer, South Dakota tornado .

These supercells then merged into a line and moved into southern Minnesota during the early evening and continued to track eastward. As it moved through Wisconsin it became a bow echo producing multiple downbursts and significant wind damage. Thunderstorm wind gusts across central and southern Wisconsin were in the 70-100 mph range, with a few reports to 110 mph. In southern Dodge County, there was an isolated report of 128 mph!

Here is a list of the Local Storm Reports issued for the event from 10:28 PM May 30, 1998 to 4:05 AM May 31, 1998. You can track the reports as the move from the northwest to southeast across Wisconsin.

The image to the right is a warning from the May 30-31, 1998 event while the one shown below is from the August 10, 2020 derecho event that moved through Iowa and Illinois. The red boxes show how the text in our Severe Thunderstorm Warnings has changed. Overall the changes help organize the information and provide more detail to the user so that they can make important safety decisions.

• In box 1 you can see the hazard(s) expected from the storm, the source backing up the warning, and the expected impacts are listed. This adds extra detail and also allows the user to directly focus on this information.

• In box 2 you can see that the expected impacted locations are included, again this adds extra value to the user.

• In box 3 you can see that a title has been added for precautionary/preparedness actions.

• In box 4 included latitude and longitude locations along with the time, motion, and location of the storm.

• In box 5 is what we call warning tags, you can look at this to directly see what the threat is without the extra detail.