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April 5, 2003
Storm Chase
Northwest Texas
Editor:
Putnam E. Reiter
Forecast/Setup -
Risk Area: Moderate - Enhanced
(10% hatched area on tornado probability graphic).
Initial Target Area: Northwest Texas
SPC and NWS forecasters did a great job on this event. My only gripe is storm
motion mentioned in the NWS warnings.
The 500mb flow was characterized by a shortwave trof moving into the Arizona
region by late afternoon. A surface low developed in response to this system
over northeast New Mexico. 850mb low also located over northeast New Mexico by
6:00pm, per GFS initialization. The 700mb wave was located in northwest
New Mexico.
A cold front passed through Oklahoma on Friday and moved to near Waco, before
stalling early Saturday morning. This front actually drifted a little farther
south. Models, with varying degrees of intensity, returned this front north as a
warm front by late afternoon. Once the Sun was up and clouds cleared, the front
did start moving north. By 6:00pm a double warm front structure developed with
the lead front in far southern Oklahoma, characterized by 55-60F dewpoints and
the secondary front near I-20, characterized by 60+F dewpoints and southeast
winds. Surface temperatures were in the mid-70s across parts of north Texas,
south of the lead warm front.
The primary complicating factor was the ultimate location of the warm front. We
knew that the warm front would be moving north during the day. We had hopes that
it would move into far northern Texas by convective initiation, but it barely
made it north of I-20. CAPE values in the true warm sector probably reached at
least 2500 J/Kg with LIs to -6 or lower. I mention the "true warm sector"
because some of this air force fed our storms and additional convection later in
the day.
SPC Products:
SWO Day 1 -
Watches Graphics:
Risk Area -
Tornado Prob -
Damaging
Wind Prob -
Hail Prob
Some of the more interesting
local
storm reports.
Surface Maps:
Temperature -
Dewpoint -
Wind Speed -
CAPE -
Lifted Index
GFS Model:
00z Initialization
Dewpoint - Mesoeta
00z Initialization
Surface Pressure
850mb Wind
700mb Wind
500mb Wind
500mb Vorticity
The Chase -
Team 1 - Dave Smith, Rob
Ferguson, and Putnam Reiter
Team 2 - Marc Foster
Miles Driven - @550
Departure Time - 13:18 CST
Return Time - 23:22 CST
This is one of those chase summaries that I would rather not write. We left
Oklahoma City around 13:18 CST and headed south on I-44. We got word a little
later that storms had developed along the dryline. We decided to continue south
to Wichita Falls, our first thought was to stop in Lawton for a few minutes. At
Wichita Falls, Texas, we fueled up around
14:10 and headed west on Highway 277, towards Seymour. We got word that one
storm had dissipated to our north while another continued very strong near
Snyder, Texas and had a tornado. We reached Haskell around 15:38 and fueled up
again. Drove south and watch an impressive wall cloud and storm structure for
about 15 minutes. We watched the RFD rotate around the circulation and cut it
off.
Storm started gusting out on us and we took off south. our first encounter with
faith was to have our instrument package (The Scout) blown off the vehicle by 82
mph winds. This occurred at 16:00. We picked up the remains and headed south on
Highway 277 into Stranford. We then turned around and about that time lost the
amateur radio antenna (didn't know it at the time). Drove back north on
Highway 277 to try to out run the storm on the north flank. We drove
back into Haskell around 16:34 and ran into zero visibility due to hail fog. The
area looked like it had just snowed. We then drove east on Highway 380 towards
Throckmorton. We maneuvered a little bit as we noted rotation nearby a few times. At 17:18 we turned south on FM 578 to get south of the storm, it was located
southwest of us at this point. Getting into hail we turned east on Highway 209
from Murry. We then dropped south on FM 3109 and started to encounter
tennis ball hail. We pulled over to ride it out at 17:45. Damage to
vehicle: cracked but not broken windshield, will have to be replaced. Broken
light lens, will have to be replaced. A lot of hail damage to the sheet
metal roof and hood. This is when the missing antenna was noticed.
We headed home around 17:59 heading through Graham, then Wichita Falls. We
stopped in Lawton for fuel and food, and to look at the vehicle. Completed the
trip by traveling north on I-44 back to Oklahoma City.
There are several chaser accounts of the tornado near Hamlin. However, I have
not heard of any other confirmed accounts east of Haskell. The storm most likely
produced a very strong cold pool which when rotated downward by the RFD was too
cool to be wrapped into a circulation. This is what we noted a few times.
Quote of the day: When talking about discrete supercells, someone commented that
they would rather know what the storm is going to do. Discrete in meteorological
storms usually refers to spatially isolated supercells.
Read Marc's chase summary.
Lessons Learned -
- Storm motion got us
again. NWS warnings and other information indicated that the storm was moving
east at 30mph. As we rounded the front of the storm, we got hit by tennis
ball
sized hail. The storm was actually moving east-southeast at 45mph or faster.
- It is much better to take the southern route when trying to re-engage a
storm.
- New chase rule: Do not chase south of Highway 380 in Texas.
- An old one, but stay on the southern flank of a supercell.
Multimedia -
Clip 1 - Just south of Haskell
on Highway 277, heading south. The Scout is lifted off the vehicle. Expletive.
Clip 2 - Coming into Haskell after the storm passed, heading north on Highway
277.
Clip 3 - 5 miles southeast of Murry, getting softball sized hail. Expletive.
Picture 1 - Damage to the chase vehicle.
Picture 2 - The Scout as it should be.
Picture 3 - The Scout as it is now.
Picture 4 - Golfball sized hail.
Picture 5
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Our estimate of the track of the largest hail (black line). Note how the
storm never moved due east like NWS warnings said it was. The green
represents how the storm should have moved following NWS warnings.
Here is a
copy of one warning, about the time we got whacked.
Picture 6 - Where we
lost the amateur radio antenna, in Stranford, Texas.
Encounters -
Near: Haskell, Texas
Tornado: Yes, but about 30 minutes before the storm reached Haskell and us.
Wall Cloud: Yes
Severe Hail: Yes - tennis ball
Severe Wind: Yes - measured by another chaser at 82mph.
Editor's Note -
New chasers or those interested frequently complain about how the veterans
caution them on storm chasing. Like many other hobbies, time and knowledge
are very important. Even the most experienced chasers occasionally get
themselves in bad positions. Such was our situation on this chase. Several other
chasers got caught by this storm. The age-old rule of dealing with a supercell
holds here, stay on the southern flank. If we'd done that, this would have been
much different.
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