June 7, 2008

Statistics:

Initial Target: Des Moines, IA
Departure: Bolingbrook, IL 6:30 am
Arrival: Bolingbrook, IL 1:00 am
Intercepts: New Hampton, IA
Tornadoes: 0
Hail: None
Wind: Non-Severe (not measured)
Features: Wall Cloud, Shelf Cloud
Miles: 1069

Summary:

Targeted central Iowa where best instability was forecast and initiation from a surface trough.  Intercepted storm from its initiation north of Ames and followed up to Riceville, IA watching development of rain free base, wall cloud, tornado warning, and rain wrapped dissipation.  Dropped to flanking cells noting two more wall clouds, the second one with good contrast, amazing lightning, and a tail cloud that formed directly overhead.  Crossed Minnesota border to intercept larger tornado warned supercells, but cells were gusting out in a large line.  Dropped down the line seeing the same gusting out features, before calling it a chase at Mason City.

Crew and Equipment:

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

Details:

Saturday's setup looked like it held some potential.  There was strong instability forecast in central IA, northwest flow at the 500 mb levels, and initiation was expected along a surface trough that was south of a warm front in Minnesota.  I targeted the Des Moines area, expected storms to fire early to the north and build down to the south where the instability would be better.
I made it to Des Moines, by 11 and had a nice long lunch at Jimmy John's.  A cumulus field was moving out of Nebraska and was going to pass to my north by Ames so I started heading north on 35.  I was perfectly positioned by the time the tornado watch went up early that afternoon.  I watched a cell starting to go up just to my east so I exited to follow it, it had barely started to drop oprecipitation at this point.
The storm was moving at about 40 mph and it took me a good while to catch up with it, as it continued to build.
Finally underneath I saw it a developing rain free base starting to extend away from the precipitation core.  The storm was starting to get its act together.
Looking northwest as the base bowed out a bit.
The storm was still on the small side, but it started drop a lowering on the north end of the base and quickly went tornado warned.
A developing wall cloud:
The wall cloud peaks: 
A rear flanking downdraft cut through the storm, but no tornado developed, and the base bowed out:
Scud funnel:
Horseshoe base looking north:
A couple of other cells to the west were encroaching on this storm and it started to become embedded in the precipitation.  The storm just to the west had a hook echo on the radar so I finally abandoned my storm, after watching it from its very birth.  That was the first time I was watched storm go from cumulus to wall cloud. to a rain wrapped dissipation.
It didn't take long to catch the next cell in the line as it was moving right through.  A well formed wall cloud. presented itself with a nice orange backlight.
Looking southwest at approaching wall cloud with a big white meso overhead:
There was quite a bit of rain falling through the wall cloud and my position just ahead of it.
Wall cloud passing by to the south:
As the wall cloud passed just to my south, a tail cloud formed right above me, feeding into into the wall cloud.
This wall cloud became heavily wrapped in rain and started to degrade on the radar as well so I dropped to the last storm in the line.  A third wall cloud came into view with brilliant sunbeams above it (a rare combination).  As I watched this wall cloud, a local spotter came by to chat with me for a bit and cracked open a beer.  The storm was ingesting worked over air and it started to dissolve.  I made sure it was on its way off before I bailed and ran north to some monster storms across the Minnesota border that were tornado warned.
I lost GPS and data just as I crossed the border due to some gremlin, but I had a visual on the storm at that point.  A large shelf cloud came into view with what looked like a wicked precipitation core behind it.
Another local came by to chat with me about the storm, but I had to cut our talk short as the storm was heading straight for me and I didn't want to get cored.  I bailed south of Le Roy, MN just in time to avoid getting hit.
A large line of cells went up and extended all the way into Kansas.  I dropped to different tornado warned parts of the line, but I kept seeing the same story: a whale's mouth well ahead of the storm, a shelf cloud and big precipitation core behind it.  The day was over, and I started heading for home, happy with my wall cloud catches and how well I played the setup.  That is until I heard about the wedge fest forty miles south of Bolingbrook.  A freak storm went up on a boundary in northeast Illinois and dropped several large, destructive tornadoes.  It was disheartening to envision missing that after driving over a 1000 miles with no tornadoes.
Conclusion:

I'm not counting this chase as a bust, but a "noteworthy intercept" because of the nice wall cloud catches and being able to follow a storm from birth to death.  It really stung not catching the tornadoes close to home though.  There was decent instability and very good directional shear where the Illinois storm went up, and some previously hidden boundary that trigged initiation.  One of the tornadoes passed within a mile of the building I used to work out of too.

 

Lessons Learned:

  • The best forecasting and positioning does not always yield the best storms.