5/7/97 TX chase by Roger Edwards


Roger Edwards chase account:

On Wed, 7 May 1997, Gilbert L. Sebenste typed:

> At 7:45 they (and 14 students) have a hose in Gray County, TX...near roads
> 293/70, from what I can tell. EXCELLENT gate to gate shear on that cell
> right now, and as I speak, they see another rapidly rotating wall cloud!
> Going for two!!!!!....

Rich Thompson, Jack Beven and I were chasing in the Meatwagon and had just
met up with Paul and his young flock just north of that intersection,
immediately before that probable tornado (which I have since called in to
be relayed to AMA).  Here is the chase summary:

We left Norman shortly after noon, having made a forecast target area in
the Memphis/Clarendon vicinity, and having not called back for guidance or
seen any weather data whatsoever after leaving.  We arrived at a good
lookout vantage just W of Lakeview TX after 4 pm, observing much
better vertical development to cumulus to the N and NW than 
any other direction.  This was near of the north rim of the 
Palo Duro Canyon, a noted hotspot for terrain-enhanced convective 
initiation, which we thought was quite possible.  We spent most of 
the next 2.5 hours slowly drifting north with a few long 
observation stops, between there and Clarendon.  We observed
several turkey towers bubbling and frothing above the canyon to our W, and
passed the waiting time by collecting interesting rocks, sawing off some
leafless roadside mesquite to take home and use for grill wood, and
atomizing caliche chunks with powerful swings of a softball bat.  All the
while, there were warnings (including a tornado warning) for the Dumas
cell; but it wasn't quite southeast enough to be in our forecast area and
we weren't particularly interested in it.  We felt the best S-R
flow in the area would be slightly farther SE.  [Patient chasers, we.]

We did observe an orphan anvil and some adjacent new high-based towers
distant SW (this agitated area later yielded the Hall County storm); but
it was just a little too far SW of our forecast area and too far to reach
much before sunset. [While going N to the last stop S of Clarendon, both
DOWs passed us going S.]  Finally, we observed hard towers erupting up
through some pre-existing cirrus to the NNW, just N of I-40; this cell
would later become the Gray County/LeFors supercell.  Being on the N edge
of our target area, with only a couple hours of daylight left, we decided
to head up to it (only to miss very late development of a small but
apparently photogenically tornadic storm near Memphis around 8:22 pm!).

After crossing I-40 W of Groom, it became apparent that our target storm
was just one member of a series aligned generally zonally just N of hwy
293.  We began to see evidence of a deep mesocyclone while still S
of that road. There was also a prominent but rather featureless rain-free
base distant W, S of Pampa.  We headed E on 293, paralleling and
overtaking a well-developed, rapidly rotating wall cloud.  We were driving
E about 70 mph (the speed limit on that section of 293); and individual
cloud tags in the south rim of the skirt (around the wall cloud) were
still moving E faster than us.  What fantastic rotation!  Meanwhile,
forked, staccato anvil CGs were as numerous as I have ever seen and in
all directions, prompting Jack to say that the anvil appeared to be
"walking on CGs."  Some of the strikes were occurring several miles to our
S and SE, way out into the low level inflow region, well removed from any
precip and many miles away from the meso.

We reached hwy 70, realizing quickly that we could not get NE to LeFors
before the meso crossed 70 to our N and cut us off.  So with no E road
option N of I-40, we sat  just N of the 70/293 intersection and
watched that whirling dervish of a wall cloud cross 70 to our N.  Paul
Sirvatka's vans pulled up next to us and people poured out [there was
still an unnerving number of anvil CGs around, but decreasing in
frequency].  We chatted a bit with Paul while watching the wall cloud move
to a position about 2 miles to our NE (8 SW LeFors), when a well-defined
front-lit condensation funnel appeared underneath, extending at times at
least 3/4 of the way to the ground.  Unfortunately, poor contrast and wet
ground prevented enough of a debris cloud for us to see; so until I either
see confirming video or get a good damage fix, this "probable" tornado
cannot be confirmed.  [Gilbert - can you find out for me if anyone in
Paul's crews got video of the tube?  We didn't -- see below!]

It lasted slightly more than a minute before
becoming diffuse and hidden by wrapping precip curtains.  Unfortunately,
we had made the mistake of not synchronizing our clocks; my watch said
7:39 but was probably slow; and Rich's video camera was 7 minutes faster.
Shortly thereafter, Paul talked to Gilbert and received word
that this meso had a TVS (no s***).

Rich had unknowingly left his video camera on "pause" while he *thought*
he was filming the hose, and didn't get it on tape!  I had the time to
reel off a couple stills.  HOWEVER -- It was extremely dark under that
base; and I had to shoot 1/15 sec hand-held (no outside tripod
set up due to the possibility that I could be turned into a big piece of
charcoal).  The stills may not come out.  Such are perils of chasing!

That meso got away to the NE; and a huge new one quickly formed to our NW.
This evolved within minutes into a rotating wall cloud and then a
bookend vortex for a bow echo that began surging SE toward us.  We were
pummeled with winds estimated to be near severe; but inherent human
subjective imprecision prevents us or anyone from making a scientifically
useful speed estimate.  The Meatwagon was also pelted with hail to 1.5
inches in diameter - with no damage of course.

We headed SE along 287 toward Memphis then E thru Altus to avoid the most
destructive part of the resulting MCS, meeting with Gene Rhoden and Tim
Vasquez for a late dinner.  In all, it was a very entertaining and
educational chase, with lots of rapid evolutions in storm character, as
well as lessons in patience and in photography.  Of course, I am quite
interested in any others' accounts of either this event or the two W/SW OK
supercells of 1 May (which Rich, Steve Goss and I observed).

                        ---------------------------
*** No disclaimer necessary; this is my personal account! ***
"I'm a @#$%& legend!"                  ===== Roger Edwards =====
- current chase partner                    (   ) Forecaster
                                         former NHC Forecaster
:::::::::: http://www.wildstar.net/~tornado ::::::::::
"I FEAST ON THE SMORGASBORD OF ATMOSPHERIC VIOLENCE."

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