July 29, 1996 Iowa Chase By Paul Vincent Craven

From: Paul Vincent Craven 
Storm Spotter Report
July 29, 1996

Paul Vincent Craven,AA0PE

After being caught a bit by surprise, I left work in West Des Moines at 4:00
p.m. after belatedly hearing that we were under a tornado watch.  I was
going to be chasing hot air balloons that evening, but luckily storm chasing
and balloon chasing are mutually exclusive hobbies.

I drove south on I-35 where I met up with my brother Steve (KA0ZDA).  We
headed south on I-35 driving through some heavy rain and soon passed out
from under that cell.  Didn't look like much was happening, so we continued
south towards where another cell looked to be building.  That cell looked
more impressive, but the view was obstructed and I couldn't see where that
cell was topping out at. Later radar analysis showed 500, with a mesocyclone
and hail.  The cell we had just driven through tops at 300, and no rotation.

We turned east on the exit for G50 (or there abouts, I wasn't driving) to
travel between the cells and keep an eye on them. All this while remaining
in the clear.  We soon heard on the 146.76 repeater, a ham spot a wall
cloud.  (Sorry, forgot the call.)  My brother and were exceedingly doubtful,
since NA0R at the NWS hadn't been reporting any mesocyclone on that smaller
cell, and the ham didn't see and distinctive rotation.  Well, NA0R soon came
back with a confirmation of the wall cloud and mid-level rotation, saying
that cell was loosing energy due to competition with nearby cells.

We went after the small cell, where the wall cloud had been sited. My
brother and I topped a rise and soon all doubt disappeared as a text-book
example of a wall cloud appeared ahead of us.  As we followed it, it
appeared to break-up, and we thought it might soon disappear.  We got just
ahead and to the side of it and stopped to get out of the truck.  After a
while of watching, we were able to pick out a rotating mesocyclone. Soon we
were able to pick out vapor being pulled upward into the center as the
updraft took a hold of it.  The cell passed nearly over our heads and on to
the south-east.  My father (N0PDK) also was watching the rotation in a
separate location.  After the storm had gone by, my brother and I (based on
my advice) took a turn that brought us into heavy rain and strong winds.  We
soon lost site of the wall cloud, and by the time we had gotten out of the
rain, we could not find it again.  My dad stated that most of the rotation
had dissipated, and we followed the storm to Indianola.  Most of the storm
had collapsed into heavy rain at that point, and the cloud tops weren't very
high at all.

South of us looked to be quite interesting on the radar, don't know it
anyone was down that way.

Paul Vincent Craven
West Des Moines, Iowa  USA
e-mail: paul_craven@raccoon.com
www:    http://www.raccoon.com/~pcraven
radio:  AA0PE