A Barn Was Damaged Wednesday Afternoon In Whitewater

Around 4:38 PM, Wednesday afternoon, April 29th, 2015, a barn sustained damage and debris was scattered, possibly up to a mile away, from what appears to be a gustnado/landspout feature. Witnesses said it lasted about 1 to 2 minutes. It started near the intersection of highway 89/12 (specifically hwy 89 and Willis Ray Rd) on the southwest side of Whitewater, WI and traveled southeast to near the intersection of Anderson and Clover Valley Rd.

A cluster of weak showers was moving through the area (see radar image below) when it likely interacted with the lake breeze boundary that had pushed all the way in from Lake Michigan. It should be noted that it's not at all unusual for these lake breezes to drift that far west. Typical for spring. Anyway, it is likely the combination of the showers and this boundary generated enough surface based circulation to spin up something called a gustnado, or a landspout. We'll have folks look into it in more detail on Thursday to be sure.

This type of circulation doesn't originate at the cloud level, is not a storm-scale rotation and doesn't form out of a wall cloud or mesocyclone. The scale is so small that radar will not pick up these features. The damage and severity are usually very limited, as was the case here.

Wesley T., an NWS trained storm spotter, witnessed the event and gave us great detail about how it unfolded. He saw the circulating debris stretch upward toward the cloud, it was about 100 yds wide. He indicated it looked more like a dust devil, there was no condensation funnel. Classic indicators of a gustnado/landspout.

Here's the radar right around the event time:

Whitewater is in the red box and you can see the showers are very unremarkable. The velocity data was similarly benign.

Here's an animation of the radar leading up to the damage. The first frame is paused for a long time:

Here are a series of pictures taken by Walworth County Undersheriff, Kevin Williams. He investigated the damage and spoke to many witnesses. The damage to the barn was mostly to the roofing material. There are reports that it blew off the top of one of the two silos, but a look at satellite imagery indicates that one of the silos was already missing a top.

One lesson from all this, never let your guard down when it comes to Mother Nature. A good lesson to take to heart as we enter our thunderstorm season.

Davis