08/04/08 - Corn Belt Derecho

A progressive derecho developed over eastern Iowa/northwestern Illinois on Monday evening and traversed the Corn Belt late into the night. The derecho-producing convective system left behind a large swath of damage, throwing O'Hare and Midway in chaos mode and leaving hundreds of thousands of customers without power.

I watched the convective system develop in northeast Iowa via radar and finally pulled the trigger on chasing the storm once I noticed a cold pool had developed. I headed westbound on I-88 and got off at Rochelle, rerouting on small farm roads until I neared Ashton, IL. This storm's shelf was clogged by haze (it was VERY humid) and an inflow stratus cloud. In fact, I couldn't even see the shelf cloud until the thing was literally on top of me. At that point, I had to haul east -- at about 75 mph -- in order to stay ahead of it. Unfortunately, the outflow still overtook me! This storm had forward speeds I've never witnessed before; I never even had a chance to get out of the car to snap a picture of the oncoming storm. Anyway, I finally made it to I-39 and headed south as I was being whipped by 50-60 mph winds. I proceeded to Paw Paw and then Mendota, where I snapped a few images of the "whale's mouth" the outflow had left behind (see this animated gif of the scene). I then traveled east and north, back to DeKalb, all the while being whipped by rear inflow jet winds and freshly developed convection.

Unfortunately, the whole storm complex was not very picturesque. The lightning was very intense and contained lots of + CG bolts, but it was nearly impossible to find a calm, dry spot to setup a tripod. I eventually did get a couple lightning shots at DeKalb High School as the rain slowly subsided. In conclusion, this thing was just an ugly beast. I'm glad it wasn't more intense and the trees were left standing in my yard!

Picture of "whale's mouth", taken as I was heading south on I-39.

Another picture on the "mouth".

This is the first image of a large animated gif illustrating the turbulent motion in the whale's mouth. You can even make out the sinking motion produced by the surging-to-the-ground cold air. Click the image to view the animation (note: this is a rather large image).

One of a couple bolts I was finally able to capture at DeKalb High School. This bolt was very interesting ... it looked like it wanted to strike the ground, but then had second thoughts.

Click the above radar image for an animated gif illustrating the development and progression of the derecho-producing mesoscale convective system through Iowa and northwest Illinois (note: this is a rather large image).

Click the above radar image for an animated gif illustrating the maturing derecho-producing mesoscale convective system as it swung through Chicagoland and northern Indiana (note: this is a rather large image).