June 23, 1996 Iowa Chase By Gilbert Sebenste

Chase Summary, 6/23/96: My first LP

It wasn't a great scenario. In fact, despite some major positives, it was
marginal at best. A low pressure center in southwest Iowa with a warm
front extending eastward into central IL would be the focus for convection
of interest today. Sure, winds would be southeast ahead of the front as it
continued to advance northward, but surface winds would be weak, as the
pressure gradient was minimal with the storm. Instability--oh, lots of
that. LI's at 11AM were already at -10, CAPEs 4K plus...and, a shortwave
moving through western Iowa would help enhance lift over the area, and
back the surface winds. But, a west-northwesterly 30 knot 500 MB flow and
50 knot 250 MB flow ensured any supercells would be of the HP category. So
I surmised.

SPC quickly issued a tornado watch for eastern Iowa and northwest IL early
in the afternoon. At 1:30PM, after some last minute partner hunting, Brian
Fugiel, Mike Bartosz and I left for the Quad Cities, to ponder our next
move, taking I-88 from DeKalb west.

About 3 PM, we got to Moline. We took I-88 to I-80. As we did, I really
wanted to see the latest satellite and radar. I was beginning to get some
distant static on the AM radio, but nothing close. So, the decision was
made to cruise oover to the Davenport office for a quick weather update.
As we headed for the office, continuing west on I-80, I couldn't believe
what I saw next. An F-14 fighter jet was coming right at us from the west
just above ground level over the Interstate, and flew right above the cars
and trucks with a thunderous roar, causing my engine to hesitate. Everyone
slowed to a crawl!

"WHAT THE *&%# WAS THAT?!?" I screamed, holding on to the steering wheel
tight. Then, toward the west, I could see a squadron of planes flying in
formation, heading south. I forgot...it's their annual air show! No, I
don't live near Moline, but I saw it in a PNS statement the day before at
work, as they were making a forecast for storms during parts of the show.

Well, that also means that we might not get access to the office, located
right at the airport at Davenport, where the airshow was based. After some
explaining to security officials of our intent, we were allowed to get to
the office without paying for parking (nice of them, thanks guys!).

Unfortunately, as we got to the door of the office, we were greeted by a
sign which simply stated:

SEVERE WEATHER IN PROGRESS-OFFICE CLOSED.

Oh well. Back to my AM static "radar"!!! :-)

Things were looking good. Southeast winds had begun to pick up to about
15 MPH. At 4 PM, everything around us at Moline was still capped.
Fantastic! 5K CAPES, and it's waiting for the wave to
kick things off. After watching the show for a bit, we called the
College of DuPage for some weather information. An isolated storm was
going up at Cedar Rapids. It's east of the developing line, all by
it's lonesome. Well, it's time to give this storm some company!

We took I-80 to US 61 north to US 30 west at Grand Mound. We switched
drivers so I could film, and we proceeded west towards the darkening sky.
As we appraoched, we couldn't make out any discernable base (hmmmm), so we
took US 30 into Calamus and headed north on county road Y44.

A short time later, at 4:45PM, we finally saw the rain free base to our
northwest. The storm was putting out an impressive lightning display, but
there was no wall cloud, no rotation, and no sign of supercell evolution.
Worse, surface winds were now dead calm as it headed northeast at about 30
MPH. We watched it for a bit and called COD for an update. That was the
only storm to speak of, outside of the storms in southern Iowa getting
going. We pulled over and watched it for a bit near the intersection of
Y44 and E63. Deciding we wanted to stay out ahead of it (a good thing), we
headed east on CR E63 back to US 61 and to head north. In the process,
valleys and trees would cause us to lose sight of the storm for 20
minutes.

At 5 PM, just before we turned north on 61, I noticed a couple of
mid-level inflow bands streaming north. Trees and a valley still blocked our
view. We turned north on 61, and after a few minutes of getting out of
valleys and trees, a stunning sight greeted us just north of Welton. There
was a new storm, and it was...rotating, albeit rather slowly. But where
the heck was the rain and hail? There it was, by the anvil. No, it can't
be. In Iowa? With light surface winds? With not much shear? I couldn't
believe the incredible view of the high-based LP supercell we were
watching!!!

We quickly pulled over about 3 miles north of Welton. I did a pan of the
storm with my video camera about 4 miles to our north-northwest, while
Mike and Brian snapped away with their cameras. The highly tilted barber
pole wasn't moving quickly; after we got our distant beauty shots, we
continued northward on 61 and we almost drove right under the weak
mesocyclone which was developing underneath. Only sprinkles were
encountered there. To someone who has only seen one in pictures, an LP
supercell is a really bizarre thing!

With the core of the storm just off to our north and east, we went into
Maquoketa, and turned east on SR 64. For almost an hour, we followed the
slow moving LP, which slowly evolved into a LP/classic, over the next
hour. It never produced any tornadoes or showed signs of low-level
rotation. Unfortunately, it went across the Mississippi into extreme
northwest Illinois, and we tried in vain to chase it in Jo Daviess county.
This part of the state was affected by glaciers moving south from
Canada tens of thousands of years ago, and is extremely poor (read: hilly)
chase country. After getting only glimpses of the cell over the next hour,
and knowing this wouldn't get any better as it headed into Wisconsin, we
headed home. We took 64 east across the Mississippi River to Illinois 84
north, then small roads to US route 20 near Elizabeth, and we took that to
I-39 south, then to I-88 to home in DeKalb. I had work very early the next
day, and Brian had an exam to study for. BUT...

As we got back to DeKalb, my weather radio went off. Outflow from the
storms had spawned another storm in Carroll county, which rapidly became
severe in the still unspoiled airmass over northern Illinois! But I had to
get to sleep. Besides, it will die anyway. After all, the storm is in
Illinois. Right?

After a quick shower, my weather radio sounded. Severe thunderstorm
warning for DeKalb county for a line of severe storms heading right for
me! OK, OK, you've convinced me to stay up for a while more!! :-)

I grabbed my video camera, walked out on the balcony, and taped the
incoming squall line. Radar showed a bow echo with the crux of the bow
pointing right at DeKalb! A strong gust front, producing winds of about 50
MPH, forced me back inside as the rain came down in buckets with an
incredible lightning display. Across the street, lightning hit a tree
with a BANG! This was neat! After about 20 minutes, the storm moved east
after dumping .73" of rain on us. Then, it was over, after an impressive
lightning display to my east.

It wasn't the best of chase days, but for late June, not bad! The only
supercells that did anything were along the front in southern Iowa, and
along the cold front in Nebraska, where lift was enhanced by the
approaching short wave.

Gilbert

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Gilbert Sebenste                                                     ********
Internet: sebenste@geog.niu.edu    (My opinions only!)                 *****
Owner of the Storm Chaser Homepage                                     ***
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