07/27/11 Northern Illinois Supercells

A developing (LP) supercell along U.S. 20
north of Worthington, IA

Last Wednesday, featured a local storm chase for my standards in eastern Iowa and northern Illinois. I was forecasting for this potential chase day for a few days and kept a close eye on this date. It appeared that along a surface warm front on the edge of the heat dome the "cap" (warm-layer aloft) could be broken which meant a chance for supercells and maybe even tornadoes. I remained skeptical however since Iowa is notorious for busts thanks to warm 700mb temps in late-July. With that being said, I pulled the plug on my day off to take a chance on this chase day since I hadn't chased in nearly over a month. It was time to get a supercell and/or tornado right? I started the day in my hometown "rooming" at my parent's house the night before. By noon, I was out the door initially targeting an outflow boundary near Waterloo, IA. I arrived to my target shortly after 2:00pm. After enjoying some Arby's in the area for lunch I kept a close eye on the atmospheric setup. I quickly began to notice some towering (Cu) cumulus to my northeast. This is when I had to make a "gutsy" decision or well you can use another word for it if you wish. All the mesoscale models were indicating storms initiating in my area, but I wasn't buying it. I relied solely on instinct rather than models that didn't perform well the previous day for chasers as well. Everything seemed it was shifting east where a weaker cap resided so I made the call to head east on U.S. 20 before any storm initiated. I found myself along the warm front in an area characterized with extreme instability in place with 5,000J/kg of CAPE, 0-6km shear at 40kts, a supercell composite of 20, 0-3km shear nearing 300m2/s2, and a moist boundary-layer. This area seemed prime for supercells along the warm front, but it all was conditional on whether the cap would break. Storms began to initiate however after 5:00pm. The most photogenic photos I took actually were at this moment as storms were (LP) low-precipitation in nature creating some awesome supercell structure at this point. The first cell developed along U.S. 20 north of Worthington, IA and would later interact with the warm front off to the east. I continued to head east keeping up with the developing supercell. I ended up getting flooded in Dubuque, IA. Good thing I got out of there before the real "deluge" began as that area was already starting to flood severely. Once across the Mississippi River that supercell started really getting going wrapping up a nice hook on radar right behind me along U.S. 20. I jogged southeast along U.S. 20 setting up shop on the north-side of Galena, IL looking northwest as the supercell approached. This is where I witnessed intermittent brief tornado touchdowns to my north/northwest. These touchdowns however, lasted only a few seconds where it was hard to discern any damage. The topography in this area also didn't help much. A local sheriff from Galena, IL also observed these vorticies as well at my location. Anyhow, once the storm gobbled me up I progressed further and further south to get out of the flooding while taking some photos of the developing MCS as it began to interact with its cold pool. Once sunset came I called it a chase quite happy with the chase day. I've added photos and some video below:

Condensation funnel with vorticies responsible for
some intermittent tornado touchdowns
north/northwest of Galena, IL

First shot of the developing mesocyclone
(rotating updraft)

Cool shot with this cell phone tower in
the foreground showing off the vertical nature
of this rotating updraft...

(LP) supercell a couple miles to my west along U.S. 20

Beautiful (LP) supercell for late-July!

You spin me right around, baby
right around like a record, baby
right round, round round...

Cool perspective here...now that's meeting under the meso eh?
(also notice the mobile weather station giving you a clue
of how the surface winds are blowing (SE))

Supercell crosses the Mississippi River
looking due west towards the river...

Storms begin to interact creating a
cold pool and shelf cloud (above)

Evil looking shelf cloud at dusk...

One last storm photo at least before dark...

 
I've added a YouTube time-lapse from
my GoPro camera (above)

A successful chase day this ended up being for myself. Storm reports can be found here. I still may chase locally in the next couple of months if it's "warranted". Stay tuned if I do end up again on the open road. Until then...