June 22 Damaging Wind Summary

On the morning of June 22, 2015, a line of severe thunderstorms known as a derecho moved across the Upper Midwest. A derecho is a relatively rare phenomenon in which a swath of damage from severe wind gusts (at least 58 mph) extends across at least 240 miles. These storms started during the early morning hours over the Dakotas before moving across Iowa and Minnesota. The storms moved into southwestern Wisconsin by mid morning where they continued to produce very high winds, up to 100 mph in some locations. The storms began to dissipate upon reaching central Wisconsin, although they continued to produce damage all the way into the Milwaukee metro area.

High wind damage reports and high wind measurements from Monday morning. Many of these points represent winds greater than 58 mph, although most in central and eastern Wisconsin are below severe criteria.

After getting multiple reports of extensive damage from these storms, especially in Green, Lafayette, and Iowa counties, we sent a survey team out to examine the damage and determine the strength of storms that moved through the region. The damage surveys revealed several instances in which the winds exceeded 80 mph, and in some places may have reached up to 100 mph. Much of the damage we found was in the form of trees snapped or knocked down, but there were several houses with roof damage and some out buildings with extensive structural damage. Below is a map of the locations that we surveyed along with pictures of some of the more impressive damage.

A closer look at high wind damage reports in our forecast area (blue) and locations where we surveyed damage (white). Some of the blue points and all of the white points represent winds greater than 58 mph.


Barn damage east of Platteville in Lafayette County. 90-100 mph winds.	Uprooted tree in Belmont in Lafayette county. 90-100 mph winds.

Tree knocked over in Hollandale in Iowa County. 90 mph winds.	Bleachers blown 20 yards in Hollandale in Iowa County. 90 mph winds.

Tree trunk snapped in far NW Green County. 90 mph winds.	Tree trunk snapped in far NW Green County. 90 mph winds.

Herzog