June 6, 2007

Statistics:

Initial Target: Kearney, NE
Departure: Bolingbrook, IL 5:30 am
Arrival: Bolingbrook, IL 11:00 am
Intercepts: Taylor, NE
Tornadoes: 0
Hail: None
Wind: Non-Severe (not measured)
Features: RFB, possible wall cloud
Miles: 1558

Summary:

Greatly hyped, day 3 moderate, Nebraska/South Dakota setup.  Chad Cowan and I left Bolingbrook early, rendezvousing with Andrew Pritchard and Scott Kampas at the Iowa 80 Truck Stop.  Targeted south central Nebraska along I-80.  West of Kearney, went north to Taylor.  Waited east of Taylor for initiation.  Line fired on dryline near sunset, intercepted near Taylor noting an RFB, and some minor rotation/lowerings.  Dropped down the line to catch Tail-End-Charlie, but storms lined out after dark with dramatic, backlit scud but no rotation.  Called it a bust at about 10 pm and headed for home.

Crew and Equipment:

Chase team included Chad Cowan, Andrew Pritchard, and Scott Kampas.  Equipment consisted of a TH-F6A Tribander, and GPS/Cell Phone equipped laptop.  Photography by Skip Talbot.

Details:

I knew it would happen.  The models spit out a huge setup the day before I had to leave for a big conference in Providence, RI.  I was presenting my research work at the conference, so it was a big deal.  I absolutely could not miss my flight on Thursday, and chasing on Wednesday (especially a long range chase) would be extremely risky.  If I got stuck in the mud or the car broke down I would most likely miss the conference.  Well, the models were showing a combination of extreme instability, shear, and helicity.  Its quite rare for all of these parameters to line up.  Severe parameters were off the charts.
I was able to juggle my tickets and get an afternoon flight out of Chicago on Thursday.  If we were back on 80 in Nebraska before midnight, I could make it back with a few hours to spare to get ready and catch my flight.  Given the extreme parameters (1km EHI's were up to 18 at one point), I had several chase partner requests.  Chad, Drew, and Scott all agreed to chase with me and split gas expenses (which helped considering gas was well over $3).  Ben Leitschuh also wanted to caravan, which could save the day if one of the cars broke down.

The big "if" in this chase was the cap.  The models were showing a wicked amount of CINH, and the Cap Index was solid east of the dryline.  There was some erosion right on the dryline later in the day, but many were worried if storms would go up before sunset, if at all.  Chad crashed my place the night before and we left super early.  Based on RUC guidance, we made for south central Nebraska.  Instability was still very high here, collocated with the best shear and instability, and the the lower levels were spiking vertical velocities after 0z.  We left early in the morning instead of the night before, knowing that the cap would break late in the day (if it did) and we'd have time to make it out there.  Drew and Scott joined us at the World's Largest Truck Stop off of I-80 west of Davenport.  We traded off driving, and stopped for some grub at the Quiznos just west of Omaha, NE. 

One of the amazing features of this setup was a 974 surface low bombing out in South Dakota.  The pressure gradients that resulted created incredible surface winds.  In central Nebraska we drove through a large dust storm as winds howled well above 30 mph.  In the height of the dust storm, visibility was usually more than a mile, but thick streams of dust would occasionally cross the highway reducing visibility to a tenth of a mile.  We heard reports that trucks and cars were being pushed off the road, and that wide areas of wind damage, including including downed trees and power poles, were occurring in Kansas.

We continued west to Elm Creek, where the decision was made to move north where some of the parameters were a little more favorable.  We wound up in Taylor, NE with blue skies overhead and no cell signal.  I was able to locate wifi under some shade, however, and we sat there for awhile waiting for something to change.  The dryline looked like it was getting rather close so we got antsy and moved east several miles. 

We sat under a blue dome, not a cloud in the sky, waiting for the cap to break.  The strong winds were whipping sand off the dunes.
With about an hour before sunset, the dryline finally lit up.  Multiple cells formed in a line right on the boundary.  We did a 180 and raced back west toward the developing storms.  The sun slipping below an anvil:
A more east-west orientated line of storms got our attention as it was ahead of the dryline.  We intercepted near Taylor with a rather high based RFB coming into view.
We watched the storm for several minutes noting some minor rotation and lowerings in an area that appeared to be interacting with an RFD.  The storm never really got its act together and we dropped down the line after a tornado warned Tail-End-Charlie.
We picked up a few chasers on the ham rig including Chris Wilburn.  We were all heading down to Tail-End-Charlie.  By the time we got there though it was after dark, and the storms were lining out.  There was some dramatic looking scud condensing under the bases, however.  We stuck around for a few minutes until we were sure the show was over and then started heading back to 80 to start the long trek home.
In Grand Island we stopped at a truck stop for some dinner.  The short handed staff was terribly slow so dinner cost us about two hours.  Darin Brunin and Dick McGowan were getting gas at the same stop and came in to say hi.  We took turns driving through the night, each of us lasting about an hour before we had to rotate.  The new day 1 for Thursday surprised me with a high risk including a 30% hatched tornado probability over all of Wisconsin.  I wasn't expecting such a high probability given the unidirectional wind fields.  I dropped Scott and Drew off at their car at about 7 am and they got ready to chase Iowa.  Chad got a hold of Ben Leitschuh who wound up not chasing Wednesday, but was going for the high risk on Thursday.  We met Ben at the Dekalb oasis where I dropped Chad off.  The two went north on 39 into central Wisconsin.  I was bummed about not being able to chase a high risk setup so close to home, but the conference took precedence.  I made it home by 11 am with plenty of time to spare before my flight.  Even though we busted, I had successfully pulled off a 1500 mile chase the day before an important event that I couldn't miss.
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Conclusion:

The lack of supercell structure, the great distance, and high expectations, made this chase a bust.  It could have gone a lot worse, however.  We could have cap busted and not seen any storms at all, or we could have gotten stuck and I could have missed my flight.  Only one tornado report came out of Nebraska, which was not caught by a chaser.  The South Dakota target faired much better with a few tornados intercepted by chasers.  The storms up there were rather junky and short lived, however.

 

Lessons Learned:

  • Even if the cap erodes enough for cells to fire on the dryline, a stout cap east of the dryline can keep storms from moving off the boundary and organizing.