8/19/09: Tornadoes in Central Illinois

Event Summary:

An MCS pushed ENE-ward through Missouri, and Illinois, and had a few embedded supercells in it, and was dropping tornadoes left and right.

At least two were confirmed in central Illinois. A small town of Williamsville, IL also got hit, where some houses were destroyed as well as a convenience/gas station. It seemed to be pick and choose, as I counted as many as four distinct rotations at one time. It was all just a matter of which storm the chasers wanted to choose.

Meanwhile, I'm sitting at home doing some hefty armchair chasing, and watching these embedded supercells in high resolution through GRLevel2 AE. I notice some crazy rotation just about to hit Williamsville, so I check the NROT values, and they are at 2.0+.

A yellow TVS then pops up, which showed a NROT of ~2.0 at 800ft! You will see in some of the pictures below how pronounced this rotation was.I've also created an animated image of SRV in 3D, where you can clearly see the tornado, which lasted for many scans.

A strong cold front will also push through the area, as well as into Michigan, and should bring another batch of storms, with some of them being strong to severe. I will have a look in the morning, to assess the situation.

EDIT: Check out the models this morning, and it seems we may have a few storms around here, but the severe threat is gone, and is east into Ohio area.


This is a four panel 3D display of the tornado that hit Williamsville, IL. All these pictures are at the same exact time, and location. From top left going clockwise, you see NROT, Spectrum Width, Base Velocity, and Storm Relative Velocity.


This is also a view of the Williamsville tornado in 3D. You can see in the animation, the tornado is pretty easy to spot on all the scans.

The following are a few photos of the damage in Williamsville, IL. Images courtesy of: The State Journal Register and Pantagraph