August 1st and August 2nd - different days with different weather events.
August 1st - Funnel Cloud
During the late afternoon hours of Monday, August 1st, the Milwaukee NWS Forecast office near Sullivan, WI, received several calls from law enforcement officials concerning public reports of funnel clouds in Fond du Lac and other counties in southeast Wisconsin. There were no thunderstorms in progress at the time.
There were only convective cumulus clouds which are typical for summer. However, the Lake Michigan Lake Breeze "front" moved well inland and reached to line from the city of Fond du Lac to Delafield to Waterford to the Kenosha Airport by 7 pm CDT August 1st. There may have been a weak lake breeze pushing inland from Lake Winnebago.
The convergence of winds from different directions at the lake breeze front resulted in weakly rotating columns of air just below cloud base. Overhead were the updrafts of the cumulus clouds which grabbed, lifted, and stretched the weak rotations vertically. Since the air was humid, once it was lifted sufficiently the invisible water vapor condensed into what the human eye recognizes as a funnel cloud.
This kind of a funnel cloud situation rarely escalates into a tornado.
Below are two pictures of the same funnel cloud near Oakfield, WI. These pictures, taken by Nate & Jackie Kollmann, were initially e-mailed to the weather staff at WTMJ-4 Milwaukee. They graciously forwarded these pictures to WFO Milwaukee. Click on images for larger version.
Below are 3 radar images at roughly 5 pm, 6 pm, and 7 pm CDT, showing the Lake Michigan lake breeze front pushing west. The lake breeze front shows up as a thin blue line. Click on images for larger version.
August 2nd - Scary- Looking Cloud & Large Hail
During the late afternoon hours of August 2, 2011, a broken line of strong to severe storms developed over the counties of Rock and Walworth and then moved east through Racine and Kenosha Counties. Large hail up to 2.25 inches in diameter fell in the Janesville area, and strong downburst winds toppled trees in parts of Walworth, Racine, and Kenosha Counties.
When the storms were going through the area between Elkhorn and Lake Geneva, a very low-hanging, scary-looking cloud (SLC) developed just ahead of a downdraft/downburst. Dave Nikolai took a picture of the SLC while it was passing over STH 12/67 about 3 miles or so north-northwest of downtown Lake Geneva at 531 pm CDT. Below is a picture of the scary-looking cloud.
This scary-looking cloud looked like a tornado or a funnel cloud depending on your viewing angle. Hard to believe - but it wasn't rotating (true tornadoes and true funnel clouds rotate).
Here is Dave's description: "The cloud feature was not rotating. I watched the cloud for a couple of minutes and I could clearly see the motion was slightly vertical without rotation. The air was very humid and I assumed it was visible due to condensation. The size of the cloud did not seem to change much while I observed it, obviously it got a little bigger as it approached me. ' Click on image for larger version.
Below is a radar image showing the line of storms over southeast Wisconsin about 530 pm CDt - the time the SLC picture above was taken. Click on image for larger version.
When the storms rolled through the Janesville area, they generated hail up to 2.25 inches in diameter. Damage wasn't reported, but certainly was possible with hail of this size. Below are some pictures taken by residents in the Janesville area. Click on images for larger version.