May 30, 2008

Statistics:

Initial Target: Springfield, IL
Departure: University Park, IL 2:30 pm
Arrival: Bolingbrook, IL 12:00 am
Intercepts: Waverly, Springfield, IL
Tornadoes: 1
Hail: Severe (Golf ball sized)
Wind: Non-Severe (not measured)
Features: Tornado, Wall Cloud, RFB, Shelf Cloud
Miles: 494

Summary:

After work chase, and departed with mature supercells already underway.  Caught severe warned bow echo south of Kankakee and stopped for a picture of a shelf cloud.  Missed supercell near Lincoln before it died and continued to Springfield to intercept already tornado warned supercells.  Intercepted two supercells on 72 noting wall clouds on both.  Followed rear supercell past Springfield until it weakened and double backed west of Springfield to intercept a third supercell.  Intercepted just west of Waverly IL noting very large wall cloud.  Tornado developed half mile from position and crossed escaped route.  Cored by hook with golf ball sized hail and escape route was blocked by downed trees ending chase.

Crew and Equipment:

Solo chase.  Equipment: TH-F6A Tribander, and GPS/Cell Phone equipped laptop.  Photography by Skip Talbot.

Details:

The season finally had a decent setup for central IL, but I had to do a full day of work first.  The cap and low level winds were forecast to be weak, so storms were expected to fire early and only have a brief window for a supercellular mode before turning linear.  During the day though it became apparent that the warm front would provide ample low level, backed winds, calling for a moderate risk for tornadoes.
I left work at 2:30 with storms already firing across the central part of the state and a tornado warning embedded in a line of storms just to my south.  The warning expired before I got there and I punched an east west orientated squall just to find another north south orientated severe bow echo closing in on me fast from the west.  I escaped south on 57 before it hit and I stopped for some pictures as a large shelf cloud bowed out to my north:
I left the linear storms for more discrete storms to my southwest.  An unwarned storm with what appeared to be a hook echo was passing fairly close to Lincoln.  It looked like a supercell except it had a fairly weak radar return.  It finally went tornado warned, but I was way too far east to intercept it in time.  I watched its entire life cycle as I puttered along on highway 136.  By the time I passed it, it was well embedded in a huge blob of rain.  I didn't even stop for it and made my down 55 towards some discrete, tornado warned supercells near Jacksonville heading for Springfield.
It took me a couple hours to make my way down to Springfield and I was sure these storms would be on their way out too by the time I intercepted.  They stayed together, however.  As I rounded Springfield and made my way onto 72, two twin supercells connected to each other were tracking due east just north of 72 heading for the city.  I passed a large wall cloud from the first supercell, but it was embedded in some heavy precipitation so I continued west to the other storm.
A second, more ragged, wall cloud came into view tracking right along 72.  I exited and photographed it as it passed overhead.  The cloud to ground lightning was intense so I didn't stay outside for long.  Heavy precipitation was wrapping around in the hook of the storm so I bailed south to get out of the core and paralleled the storm from an east west highway south of 72.  I spotted Mark Sefried and Darin Kaiser, and the College of DuPage chase team along the way.
I got back on 72 and followed the rear supercell as it moved into Springfield.  This finger like appendage appeared to my north behind a wall cloud.  I shot pictures of it while I drove so I couldn't stare long enough to discern rotation.  I believe this is the feature, however, that was reported as a funnel and later tornado as it moved over the city.
As I passed Springfield I saw a downdraft cut a dramatic diagonal swath out of the storm's base.  East of Springfield, 72 jogs north and would have taken me into the core of the storm so I wound up going southeast on 29 away from it.  The hook of the storm started to bow out so I bailed near Rochester and started coming back west to yet another discrete tornado warned supercell tracking along 72.  There was a large bow echo immediately behind it, which I assumed would gobble up the supercell before I got to it, however.
The supercell held its own, however, keeping ahead of the linear line.  This storm was tracking south of 72, and I had to speed like mad to get to a south road option before the supercell crossed it.  I managed to pull it off, just clipping the edge of the precipitation core, and turned back west in the town of Waverly.  As soon as I got out of town a gigantic wall cloud came into view, stretching for miles to the north and south.  Looking northwest at a big beaver tail feeding into the wall cloud.
The wall cloud was heading right for me so I positioned the van south for an escape down a gravel road.  A couple of chasers, whom I misinterpreted as locals originally, pulled in behind me.  I almost stopped to talk, but I had lingered too long and the wall cloud was now moving overhead; a very dangerous position.
I jumped into the van and started to tear off to the south down the gravel road to get out from under the wall cloud when less than a half mile to my southwest I saw a large tornadic debris cloud starting develop.  I slammed on the brakes and had a brief moment of terror before I realized that the tornado was moving due east like its parent storm and would miss me to the south.  Had I left moments earlier, however, I would have been directly in the path as the tornado crossed my gravel escape route.
I jumped out of the van and had to run to the passenger side to grab my still camera.  There was no time to get the video camera rolling.  My camera was set on a long exposure setting, and along with the low light, I managed to blur almost all of my shots from the chase.
I heard some shouting from the chasers behind me and by the time I looked back they were gone.  I stood and fired off a few blurred stills as the tornado crossed the road less than 2000 feet in front of me.  As it passed I heard the sound of a tornado for the first time: a rushing waterfall noise.  I was much too close.
As soon as the tornado crossed the road I jumped in the van and went south to pursue it, however, the storm's hook was immediately behind the tornado and I got slammed by the precipitation core.  Through the heavy rain bands I could still make out the tornadic circulation on the ground: a hundred yards across with lots of smaller vortices spinning inside of it.  As the core of the storm engulfed me I got barraged by high winds and golf ball sized hail.  I was out of the tornado's path, though, so I let out a cheer, amazed at what I had just seen and thankful that my stupid decision to linger too long under a wall cloud didn't end catastrophically.
The twisty, hilly gravel road was flooded in portions and my speed was seriously cut by the heavy rain of the storm's core.  The mudpuppy handled the road like a champ though.  My chase ended when I came across a large tree down in the road in front of me.  I would have to turn back.  I passed a few houses along the way and checked for damage but thankfully didn't see any.  By the time I was back on a paved road, the tornadic supercell had merged with a squall line and was well off to the east.  Andrew Pritchard intercepted me as I headed north and we stopped for some dinner at the Steak 'n Shake in Springfield where I told him my hair raising tale.
 
Conclusion:

This chase was my closest encounter to a tornado and the first time I could actually hear one.  This was also my first Illinois tornado since March 12, 2006, and that tornado was mere miles from this one.  The day fared better than I originally anticipated with storms maintaining supercellular characteristics for hours.  The tornado was rated EF1 with lots of tree damage, snapped power poles, but not too much damage to housing except for some destroyed garages.

 

Radar Analysis with GPS Overlay:

KILX Animated GIF (3.7 MB) Individual PNG Frames

 

Lessons Learned:

  • Don't let wall clouds pass overhead!