(6:30PM Wed, July 19th 2023) A brief recap of the local tornado outbreak that affected portions of Northern Illinois, from late in the afternoon into the evening of Wednesday, July 12th. 13 tornadoes have been confirmed across portions of North-Central and Northeastern Illinois, many of which were in the Chicago metro area. Additionally, a waterspout occurred just offshore from Chicago over Lake Michigan.
A potent disturbance (MCV) moving across Southern Wisconsin and Northern Illinois on Wednesday, along with a warm front lifting northward through Northern Illinois, were two of the bigger mechanisms aiding in this local tornado outbreak. Rapid atmospheric recovery occurred in the wake of earlier day rain/t’storm activity, with an environment supportive for severe weather just in time as the disturbance moved through. While not all parameters were great, of not was a quality flow along, good shear, a lot of vorticity, and off the charts low level shear. While this was not a classic event by any means, the off the chart low level shear and vorticity combination ensured even a convective rain shower had the opportunity to rotate and produce a tornado, in which some of the activity was exactly that.
•13 tornadoes occurred across portions of North-Central and Northeastern Illinois within a couple hour period, from the late afternoon into evening of Wednesday, July 12th.
•Many of the tornadoes occurred within the Chicago metro area.
•A waterspout occurred just off the Chicago shore of Lake Michigan, just north of Navy Pier.