Today’s Storm Analysis

Between 1:40 and 2:00pm this afternoon, a severe thunderstorm produced widespread damage in a narrow swath of Rockford.

At 1:37pm a severe thunderstorm developed southwest of Rockford. The bright pink color indicates a significant hail core. (A hail core is an area within the thunderstorm where intense lift creates a significant amount of hail…and sometimes very large hailstones). We didn’t receive any reports from this area…probably because the area is pretty rural.

At 1:41, the hail core abruptly went away. Where did it go? We all know the saying “what goes up must come down.” At 1:41pm, the hail core was falling out of the cloud. The core was probably about 7 miles tall and 2 miles wide. Imagine all of this air coming straight down to the ground. As the wind hits the ground it is sent out in a forward direction. In this case, it headed east-northeast. The first areas to be hit were around the South Rock Industrial Park at IL2 and Hwy 20 where several trees were snapped off. The Aldrich family lost numerous trees and a few power poles at the 3000 block of Clarine Lane (right behind Bing’s Drive-In).

Seven minutes later, the storm was producing severe damage on the other side of the Rock River along Brooke Road and on 9th Street in Southeast Rockford. A large tree fell at the end of 6th Street (at 23rd Av). Another tree fell on a car in the 3000 block of 9th as well as numerous trees falling on power lines in the neighborhood sending more people into the dark. This storm was so localized, it didn’t even produce significant wind at the Chicago/Rockford Int’l Airport (just two miles south).

1:56pm – It’s been nearly ten minutes since the hail core dropped over far SW Rockford. The wind gust is beginning to fan outward and diminish as it moves northeast. The Rockford Register Star reports that at this time scaffolding equipment at OSF Saint Anthony Hospital on East State Street. While the initial wind gust may have been near 80mph when it first formed, it was probably down to around 40-50mph in fifteen minutes…only to weaken more as it headed into the city’s far east side.


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This post was written by qni_it on September 25, 2007

4 Comments so far

  1. Anonymous September 26, 2007 12:03 AM

    out in dekalb, we got nothing, its like dekalb is rain repellant! we need the rain, but as long is not a repeat of the flood here in dekalb!

  2. Jim September 26, 2007 1:08 AM

    Thank you Eric for your detailed explanation on this storm! Very interesting. I’m glad that our reports on this blog help out your ‘disecting’ of the storm.

    Dekalb is rain repellant? It seems like Rockford is like that often too, when Dekalb gets rain. aha 🙂

  3. Eric Sorensen September 26, 2007 2:12 AM

    Jim: If I didn’t have the storm reports, I wouldn’t have known what happened. The more we know about storms and what they do, the better we will be at forecasting them.

    It’s fascinating stuff. Never a dull moment to be sure! -ES

  4. Anonymous September 26, 2007 3:04 AM

    well eric like u said, it was a localized event, since most of the storms otherwise were just ho hum, early autumn storms. it was nice to get the rain though.


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