Friday, June 13, 2008

06/12/08 Illinois Classic Discrete Supercells

Wall cloud forming off a classic supercell in west-central Illinois

After a frustrating chase in western Iowa the previous day a SLGT risk was issued by the SPC for my area in west-central Illinois and eastern Iowa. After lots of heating and a differential heating boundary that was set up from a Burlington, IA to Galesburg, IL line we knew today was better in the back of our minds then a SLGT risk. SPC agreed to a point with a 10% probability of tornadoes. After looking over models and data we decided today was a chase day.

Structure shot of a severe thunderstorm in Davenport, IA

I decided to take I-80 east to meet up with Chris Czapla at LaSalle/Peru in central Illinois for a backyard chase. After sitting there for an hour and a half evaluating and seeing convection fire to our north and a cumulus field overhead we knew we had instability just no lift as the strong cold front was still back just east of Des Moines, IA. However, 2 classic "flying V" supercells formed out ahead of the cold front in northeast Missouri and had confirmed tornadoes. These storms looked incredible and we couldn't pass them up. So we got back on I-80 west and then preceded to get off on I-74 south near Galesburg, IL. We knew if they held together we could get them before dark. On the way I was loving what I was seeing; classic supercells with well defined hook echos. It was something that's been hard to get this year with the HP monsters I've been chasing. Myself and Chris got greedy we wanted both supercells and believed we could get both of them. Could we? We got off I-74 and started heading west on Highway 17 toward Aledo, IL to intercept the first supercell. We got outside Aledo a few miles from Joy, IL and set up to watch the first supercell track to our northwest. We were in great position. So we started to head south on Highway 94 to avoid the rain and potential hail and get into better position on the "tail-end charlie" After snapping some photos we noticed that a storm that developed in southeast Iowa near Burlington, IA that my friend Brandon Sullivan was chasing was gonna munch up this first supercell unfortunately. So we decided to head south of Aledo. While doing this we were greeted with an awesome lightning show and shelf cloud that went through Aledo, IL. We watched rotation as well in a notch along the shelf where the supercell was getting munched from the southern storm. In our minds was no doubt "Is it gonna happen again"? As the same situation produced a tornado in central Illinois that we chased in late-May. It nearly produced for us in a field about 3 miles to our northeast. After giving up on this storm and avoiding the rain we still noticed we had a classic supercell to our southwest that looked to pass just to the north of Aledo, IL so we ended up driving north on Highway 94.

New mesocyclone with wall cloud forms

We also watched as one low-level mesocyclone weakened and new one formed as well which was also a spectacle. We were surprised it didn't drop a tornado for us, but that is usually the case when you have beautiful classic supercell structures they don't tend to TOR. The ones that do look messy or ragged like an earlier chase in central Illinois this year. We tried to keep up but our road network went to **** in a hurry with gravel roads and we were running out of daylight. So we pulled the plug on the chase. Nevertheless, the best supercell structure of the year for myself and in Illinois of all places. Illinois has yet to bust me this year unlike Nebraska and Iowa as of late which is saying something. Looks like this unusual spring-type pattern in June will change here in the next few days which should help the record flooding problems in the Midwest and the devastation in some areas from the tornadoes over the past few weeks.