Friday, July 23, 2010

Fort Atkinson, Wisconsin Tornadoes

Well the Janesville target sure panned out...

Pretty awesome day in southern Wisconsin.

I targeted the Janesville area and headed up that way around 2:30 once it became clear that sufficient destabilization was indeed going to build into the east side of the warm front across southern Wisconsin during the early evening. I didn't go after the early tornado warned storms near Madison, but instead sat in Brooklyn, WI watching disorganized messy convection try and fail over and over. Soon enough a tornado warning was slapped on it much to my dismay, but sure enough the lead cell eventually organized into a nice mini-supercell with a nice flat base. Eventually a big RFD sliced into the base and I thought surely it was about to produce, but a supercell to the west was raining all over it and everything was just getting completely soaked. I figured there was no way it was producing, and if it did I would never see it. I was in the process of ditching the storm for the cell to it's west raining all over it, when I got this nagging feeling that I should take one more look. Not a second after I hit an east option and crest a hill the stupid thing puts down a cone tornado. Way off in the rain, barely visible from my vantage point. I was absolutely furious. Furious that I left it and should have been closer, but ever so grateful that I pulled off and managed to see the darn thing.

I figured, okay fine, I'll keep up with this storm since apparently it doesn't care that it is getting crazy interfered with by the second cell behind it. I followed it all the way to about the Sumner area along Hwy 106 watching another nice rotating wall cloud over Lake Koshkonong. I literally had no more options for keeping up, so I figured the day was over with one stupid little rain wrapped cone.

Meanwhile, I head south back along 106 through the heavy precip core of the second storm and emerge to a beautiful RFB and wall cloud which has quite a circulation on the front end. I wasn't sure what road options lay ahead, but figure I have to go after this as long as possible. I manage to find a really good south option to get around the lake and as soon as I hit County Road N the storm produces the tornado of the day near Fort Atkinson. Nice little elephant trunk, that again was not on the ground very long but this time was a little stronger, much closer and much better contrast. The storm cycled a few more times coming very close to producing near Whitewater as I followed it east, but eventually I called it off as again the storm neared poor road options.

Surface obs from around 4PM show strongly backed winds along the eastern side of the warm front in SE Wisconsin. A red 'X' marks my target of Janesville, and where the tornadoes would occur.

SPC Mesoanalysis from 4 PM also shows Significant Tornado Parameter values bullseyed over south central Wisconsin near the warm front:

The RUC nailed this one. Below is the 17Z forecast EHI value for 21Z. It corresponds almost perfectly to the map above:

0-3km surface cape and surface vorticity also centered on southern Wisconsin.

Initial supercell with major RFD cut near Edgerton:

First tornado near Edgerton. It's there... just left of the tree.

Last view of the lead storm as seen atop a nice big soaking wet hill that I had to hike to get a view of the base near Sumner. I figured once I start to have to go on hikes to see the storm, it's time to call it:

This guy greeted me emerging out of the precip core just east of Edgerton, on the second storm now.

Video capture of the tornado near Fort Atkinson:

What a nice chase day. Targeted and executed well for once this year, as both tornadoes were within about 8-10 miles of my target of Janesville from 24 hours out, and I didn't have to drive more than an hour away from home. Met up with Scott Weberpal and Chris Gullikson in Janesville for dinner and then made my lightning illuminated way back to DeKalb.


Dann Cianca said...

Yeah! Nice catch!!

Andrew Pritchard said...

Thanks Dann!

Anonymous said...

Thank You from a stationary spotter, who was stationed in the deep downtown area!

Anonymous said...

I remeber this storm very well, I was sitting at the front door watching it pass.