Something For The Weather Weenie's

Lets discuss something absolutely incredible that happened near Chicago last night. If your not well informed about meteorological terminology then this post may not be for you. Last night there was a nasty severe weather complex that raced through Chicago. There was a game at Wrigley Field and the had to evacuate due to a tornado warning. The only actual report I have seen that may indicate a tornado was a report of a funnel cloud. Most damage reports were from straight-line winds. In order to get any type of convection, you need instability, moisture, and lift. All three were in doubt present last night, and the amounts of some of them are insane.

Below are 00z August 5 (8pm August 4)soundings in the Chicago region.

00z Sounding out of Davenport, Iowa



00z Sounding out of Lincoln, Illinois.



One of the things that sticks out at me is how positively buoyant surface parcels are if they are lifted. The Convective Available Potential Energy (CAPE) was through the roof. This shows how much an air parcel can rise and also how quickly it can rise if it is lifted. Surface-based CAPE (SBCAPE) was 6,600 J/kg and Most Unstable Cape (MUCAPE) was nearly 7,000 J/kg. Lifted Indexes (LI's) was -13 and Precipitable Water was 1.93 inches. If you notice the the temperature profile (red) and dew-point profile (green), they are not together meaning there is some dry-air to overcome in the storms. This adds to the downward momentum from severe convection. There is even a parameter for this called DCAPE or downward CAPE. This was also through the roof on the Davenport sounding with a value of 1610 J/kg. You think these values are high.. just wait. The Lincoln sounding showed even more instability. SBCAPE and MUCAPE was nearly 8,500 J/kg.. I have no words for this.. that is just INSANE. To put it in perspective, we see SBCAPE and MUCAPE more towards 1500-3000 J/kg over the summer with occasional times where these values can get close to 4,000 J/kg. DCAPE at Lincoln was almost 2,000 Jkg. Still INSANE. Precipitable water was also 1.93 inches at Lincoln. So there is no question there was instability and moisture. What about lift? There was a surface front across the region, and even a minor shortwave in the middle levels that provided for necessary lift. Here is a 700mb analysis map at 00z. Pay attention to the minor dip in the lines near the Great Lakes. To the right of the dip is usually where lift is located..



Now for some video footage.... first one taken in Chicago looking towards Wrigley field.. with the eery tornado siren in the backgroud.. Notice how the stadium basically dissappears with the rain and strong winds ( reports of winds near 90 mph). The second is some footage from someone who went to the game. The third is some amazing footage of lightning I believe after the worst of the storm moved through.