5/1/97 IL chase by Martin Lisius



Subject: May 1 Chase Summary-Lisius

It was nice to see a 24 hour forecast verify to within about 15 miles.

The afternoon before, Al Moller and I had an interesting conversation for the
day to come.  After looking at a lot of data, it looked like the CDS area would
be a good spot to target for a May 1 chase.  From that time on conditions seemed
to be coming together near CDS.  By late morning, a plume of moisture could
easily be seen on satellite stretching from SW Texas straight north to near and
just west of CDS.  dewpoint at CDS was 54 at noon and expected to rise.

Al, Jesse (NWSFO-FTW) and I departed around noon for CDS.  I listened to NOAA
Weather Radio out of SPS on the way and noted that dewpoints were rising and
pressure was falling steadily every hour.  Just east of CDS we spotted a young
Cb through Cu to our WNW.  Between CDS and Memphis we encountered heavy dust as
inflow plowed into the storm.  We paused about 5 miles south of Memphis and
watched the storm really wind up.  A severe thunderstorm warning had been issued
for our county.  Radar indicated that the storm was moving NE at 40.

We chased the storm NE through Wellington and into OK.  It seemed to weaken for
a while and then appeared to strengthen again near Vinson where we watched a
near-wall cloud spin close to the ground.  I call it that because it was never
really an established wall cloud.  This is as close to a tornado that the storm
would get for us.

We tracked the storm for a while and visited with other chasers along the way.

It was good to see Roger Edwards, Tim Marshall, Gene Rhoden, Jim Leonard, Paul
Janish, and others out there in a sort of "Storm Season '97 Kick-Off."  Watching
Al get excited was a sure sign that the season had finally arrived.

We stopped in the bright sun at Lone Wolf and watched the storm move off to the
east.  Beautiful, sun-lit towers bellowed upward.  Al shot some stills while I
shot 35mm timelapse.

Al of a sudden, a small tower appeared to our WNW blocking out the sun.  There
was still plenty of moist air between us and the dryline which was way off to
the west in the Texas Panhandle.  Anything could still go up behind us....and it
did!

We drove west and within 15 minutes the small tower had exploded in to a
full-fledged thunderstorm with large, hard-edged towers, beautiful knuckled
anvil and a broad, low-hanging base.  Unfortunately, we had only about 30
minutes of sun left.  We stoppped and took pictures of this majestic storm.  I
shot video using a 17X telephoto lens.  The next day, I looked at the video and
enjoyed watching orange towers shoot almost straight up.  This was not timelapse
but rather "real time."  Still, it looked like timelapse.

Soon it was dark and quite cool.  We watched a few nice CC bolts zip out of the
storm and then departed.

Why did the first storm we followed for so long NOT produce a tornado?

So many chasers are asking this question.

I think that it was a typical first day of recovery event.  Moisture WAS there
but maybe just a couple dewpoint degrees too low to get over the tornadic
threshhold.

Another thing.  It appeared that the storm had crossed north of the warm front.
It was certainly warmer and muggier in the Memphis area where the storm was
intensifying.  But once in OK, the air seemed a bit cooler.  Not cold, just a
few degrees cooler.  The storm still had pretty good juice, just not the high
octane grade that existed near the Red River.

This is very interesting since just 24 hours earlier, Al and I talked about the
possibility of a storm crossing the progged warm front the next day.  We
discussed specific events when that occured.  Some storms still produced
tornadoes, others appeared to weaken.  An interesting topic I will research
further.

The storm crossed north of the front and stabilized...so to speak.  That's
basically what appears to have happened.

That process did not kill the storm initially.  It was still a nice supercell
north of the front.  But, given another hour in its life south of the border, it
may have produced not only a tornado but perhaps a SIGNIFICANT tornado!

April 10 still appears to be the best chase day of the season so far.  But, May
1 was the first decent chase of the year for me, Al Moller and many of those out
there.  It was worth the trip and probably just a "warm up" for things to come.

Martin Lisius

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