June 29, 2014

Statistics

Initial Target

Start

End

Storm Intercepts

Tornadoes

Hail

Wind

Features

Miles

Syracuse, NE

Omaha, NE 9:00 AM 6/29/2014

Des Moines, IA 9:00 PM 6/29/2014

Shelby, IA

0 mph

Funnel, Wall Cloud

841

Summary

Warm front setup across western IA. Targeted se NE for initiation but went north of Omaha for developing storms in western of Iowa. Intercepted supercell with wall cloud and pursued east noting well defined funnel 1/3 condensed to ground. Positive CG barrage followed before storm gusted out.

Crew and Equipment

Chase partners: COD Trip 5. Equipment: Canon 60D, Canon t2i, Canon EFS 10-22, Canon EF 50mm, Sony HDR-xr500v..

Video

Map

Details

Day 8 for College of Dupage thumderstorm lab trip 5 was a down day/travel day. We headed east toward the next day's target, stopping along the way in Cawker City, KS to visit the world's largest ball of twine. The quirky attraction is a tourist trap that draws many storm chasers on their down days and is about the only thing in the tiny town, or in the sparse corner of northeast Kansas.

Trip 5 group shot

After lunch we headed up to Valley, NE to visit the National Weather Service office in charge of the Omaha area where we were invited for a tour and to watch a rawinsonde launch.

Watching the balloon launch that gathers the 0z upper air data:

The rawinsonde data and the guidance from the Omaha/Valley NWS office would b crucial for the next day's storm chase which was forecast to occur in their coverage area.

We spent the night in Omaha in a plush Courtyard Marriot. Day 9 looked to have the best shot at a tornado thus far on the trip with a moderately unstable warm sector and boundaries draped across eastern Nebraska that would initiate storms, with ample shear to support supercells and a few tornadoes. We picked an inital target in southeast Nebraska where lapse rates and shear/instability combinations looked most favorable. After killing time in a small residential park in Syracuse, we spotted storm initiation just north of Omaha along a sagging outflow boundary and decided to move in for the intercept.

Wall Cloud
4 miles WSW of Missouri Valley, IA
5:10 PM

We caught the storm on the Iowa side of the Missouri river just north of Omaha. We were greeted by a nice rain free base and a wall cloud soon condensed underneath. It looked like we had perfect timing and positioning as the fledgling supercell matured right in front of us.

RFD Clear Slot
Missouri Valley, IA
5:26 PM

We watched the storm track east just north of us. A big rear flanking downdraft surge cut a huge clear slot into the updraft base. This process can precede tornadogenesis, but the storm remained quiet during this cycle. Perhaps it just hadn't matured enough or we didn't have the right ingredients.

Funnel
5 miles NNW of Shelby, IA
6:11 PM

We got back on the road to track the storm east. Chaser traffic was some of the thickest I had seen all year, probably because it was a Sunday and the Pilger and Coleridge events were still fresh on people's minds. The roads got a little squirrely and the storm appeared to gust out a couple times but it finally organized just as we were in prefect intercept position again. We stopped atop a hill on a gravel road outside of Shelby, IA as a very robust wall cloud churned to our north. Thick inflow tails fed into the feature from the north. The wall cloud spun rapidly looking like a bowl and in the center of the bowl a point started to form. The dark funnel cloud descended a third of the way down from the base moving east over the Iowa farmland. I thought for sure we were going to get a nice tornado. The structure and funnel cloud looked great. It wasn't to be, however. The funnel lasted only a a minute before dissipating, and we soon had to scramble to get back on the gravel roads to avoid being run over by the storm's rear flanking core.

Block Wall Cloud
Exira, IA
7:17 PM

A couple tornado reports came in on the storm, either for the funnel we had just seen or other brief circulations. Despite the funnel and other reports, the Omaha/Valley office we had just visited withheld issuing a tornado warning on the storm. There was some discussion in the van about whether or not they should have. I thought the structure prompted a warning, but ultimately if the storm had failed to produce a real tornado threat, the warning would have busted.

We caught an intense positively charged cloud to ground lightning barage as we moved east. Everyone stayed in the vans as these CG barages can be quite dangerous. East of Exira, IA we were ahead of the storm again. A large block wall cloud was moving east just north of town.

Wispy tendrils moved around underneath the ground scraping wall cloud as it moved north of us. It might have been weak tornadic attempts, or just scud being kicked up by outflow as the storm started to gust out. We didn't see anything conclusively tornadic, and as the storm begin to gust out we called it a chase.

It was the night before the last chase and Trip 5 still hadn't gotten a tornado despite being so close on this chase. Perhaps a sacrificial fire to the weather gods would turn our luck around as the next day was the last chase of the trip.

Conclusion

This chase was the closest Trip 5 came to catching a tornado. The funnel under the robust wall cloud is also about the closest I've come to seeing a storm produce a tornado that didn't. Tornado reports did come in on the storm, however, but they appeared to be fairly brief and weak. Other storms in the region produced tornadoes but mainly after dark. The robust wall cloud and funnel was still an exciting catch for the tour and one of the highlights of the trip.

Lessons Learned

Supercells that look close to producing tornadoes may not prompt a tornado warning, so watch these storms closely.
Avoid the center of Des Moines if you're near a group that hasn't caught a tornado after a 10 day tour.

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