April 7,
2002
Storm Chase
Northwest Texas
Editor: Putnam
Reiter
Forecast/Setup -
Risk Area: Moderate
Initial Target Area: Northwest Texas
The main issue of the day was
thermodynamics, as the dynamic parameters were in place. Reference SPC Day
1 issued at 16:30z. Showers and thunderstorms had been ongoing across parts
of the threat area for 24 hours. This resulted in a very cool surface layer
across all of Oklahoma and much of north Texas.
An area of clearing developed
around San Angelo around 10:00 CDT, this area spread east and northeast to
Abilene. By 14:00 CDT, moderate to high instability had developed with CAPE
values estimated near 3000 J/Kg and LIs to -8. A convergence area also
developed in this region. The result was rapid storm development by 14:45
CDT. Our storm became a supercell and produced a tornado around 15:45 CDT.
The tornado dissipated around 16:00 CDT.
Looking at the referenced
maps, it appears that this storm moved into a region of limited surface
heating and hence instability. The warm front was about 10 miles north of
the storm and general sky conditions to the east of the storm were mostly
cloudy. The surface temperature was around 68F in the environment near and
ahead of the storm, just of east of Throckmorton. Shortly after passing
over Throckmorton the storm began to evolve into a squall line. Two areas
of rotation developed, one near Padgett and the other near Pruitt. Neither
would amount to much, but Olney (northeast of Padgett) would receive wind
damage. Our estimates place the wind speed around 60 mph.
By the time the storms reach
Newcastle a squall line had evolved.
The Chase -
Team 1 - David Underwood, Rob
Ferguson, and Putnam Reiter
Miles Driven - 415
Departure Time - 13:00 CDT
Return Time - 21:15 CDT
The group had been watching
this day for a while. Pretty much ever since it popped up on the numerical
models. Given the somewhat slow year so far; we have been anxious to get
out and find a storm.
Early morning indications were
that the best activity would be south of I-20. Storms Prediction Center (SPC)
had this covered in their 13:00z outlook. While many parameters were
in-place for severe weather; north of I-20 heating was lacking at the time.
Around 10:00 CDT clouds began to clear across parts of Texas, allowing
strong surface heating.
SPC noted this in their 16:30z outlook which upgraded areas north of I-20 to
a Moderate Risk.
Thinking that nothing would
happen when we first got out of bed; we had dropped our interest in chasing
for the day. A review of the SPC outlook would change that notion. We
scrambled the group and headed southwest to Lawton. From that point we made
our way to Archer City in northwest Texas. Around 15:45 CDT amateur radio
reports indicated a
multiple vortex tornado around HWY 380 and HWY 222 or just west of
Throckmorton. We finally got into Newcastle, after the tornado had
dissipated. Chaser from OU got this tornado on tape.
We waited around for a while
to determine what the activity would do. At this time the storms seemed to
be changing modes to a squall line and that ended up being the case. We
headed back north and went through Olney. As we got into town where we
noticed damage, which we think was straight line winds. We took some
pictures and video of the
area. After that we headed back home.
Lessons Learned -
The main lesson from this
event would be timing, as ours was off a little. One could argue that
not analyzing morning data also caused a problem. Many times these
easily season chases end up being governed by rapid surface heating due
to isolated cloud breaks.
Encounters -
Engaged Storm: Yes -
Newcastle, Texas
Tornado: No
Funnel: No
Hail (larger than 0.75 inches): No
Wall Cloud: No
Wind (above 57.4 mph): No
