On June 21, the Amarillo metropolitan area experienced perhaps the
worst wind and hail event in it's history. Numerous reports of baseball
to softball size hail were reported mainly west of interstate 27 in
Amarillo. While hail this large isn't that uncommon in the Panhandles
region, what is uncommon is the fact that the hail fell over such
a large area which was densely populated. In addition, 7 brief tornadoes
occurred with this storm though none were within the city limits of
Amarillo. Preliminary estimates put damages possibly as high as $100
million to homes, vehicles, businesses, and other property. Below
is a meteorological description of how events unfolded during the
late afternoon and evening of Monday, June 21.
The Storm Prediction Center had the entire Texas and Oklahoma panhandles
outlooked for a slight risk of severe weather due to moderate instability
and numerous boundaries across the area. A cold front had become
stationary in the northern Texas panhandle, while an outflow boundary
from thunderstorms the previous night in Oklahoma was moving westward
across the central Texas panhandle. Perhaps most significant of
all was a weak area of low pressure developing along the outflow
boundary during the day in western Potter county and eastern Oldham
county. This low would locally enhance the surface pressure gradient
causing winds to increase from the east and southeast across the
central panhandles. The low would also cause the front which had
become stationary in the northern panhandles, to make one final
push to the south and lay along the Canadian River valley. Amazingly
it was a feature called horizontal convective rolls, which is common
to the tropical Gulf coast region, that would cause the first thunderstorms
to begin. Horizontal convective rolls occur when low level shear
causes developing cumulus clouds to organize into many linear rows
resembling furrows in a field.
One horizontal roll became especially pronounced and intersected
the front near the Canadian River and highway 87 about 15 miles
north of Amarillo. The first thunderstorm developed in this location
and a spotter reported penny size hail at 5:27 pm CDT. A severe
thunderstorm warning was issued for Potter county at this same time
and even though this first thunderstorm dissipated, rapid development
was noted further west. A second severe thunderstorm developed near
Valley de Oro where golfball size hail was reported at 5:45 pm.
The thunderstorm tried to move toward the northeast however strong
convergence along the front and convective rolls caused the storm
to continually redevelop and remain in one place. Southeast surface
winds enhanced by the low in eastern Oldham county created shear
great enough for the storm to begin to tilt and rotate. Spotters
from the surrounding area began to converge on the storm and its
rotation could even be observed from our office located in east
Amarillo near Rick Husband airport.
The initial severe thunderstorm warning was due to expire at 6:30
pm and a tornado warning was then issued due to the strong rotation
observed with the storm both visually and by radar. Despite the
strong low level rotation, only brief funnel clouds were observed
for the next half hour. By 7:00 pm, the developing cold pool from
the heavy rain and hail began pushing the front slowly south, further
enhancing the rotation within the low levels of the thunderstorm.
Finally at 7:15 pm, the first of four brief tornadoes was observed
3 miles west of Bushland. It was also at this time that the rear
flank downdraft would alter the storm's motion as it began moving
towards the southeast at about 20 mph, directly towards the western
half of Amarillo. A tornado warning was reissued for Potter county
and another was issued for Randall county at 7:30 pm, however it
would not be tornados but rather hail and strong straight line winds
that would be doing the damage in Amarillo. Baseball to softball
size hail fell across western Amarillo with most damage occuring
west of Bell St. Windows and skylights were especially vulnerable
to the hail and once broken, allowed one to two inches of rain into
the structure adding to the damage. Strong straight line winds caused
other damage including overturning several travel trailers and boats.
At 7:56 pm NWS doppler radar indicated a very pronounced hook in
the reflectivity product over southwest Amarillo, at which time
a brief tornado was reported near McCormick road 4 miles west of
I-27. It was also at this time that NWS doppler radar indicated
storm relative motion winds at 1,000 ft of 140 mph heading into
the storm, with about 75 mph storm relative winds heading away from
the storm.
The thunderstorm went through an initial occlusion phase where
the hook echo briefly dissappeared but it then reappeared at about
8:16 pm as the storm crossed I-27 between Amarillo and Canyon. At
8:17 pm another brief tornado formed at the intersection of FM 1541
and Nance Road and was the only one known to have caused damage.
The tornado was only on the ground for 2 minutes but caused minor
damage to 3 homes and major damage to a fourth when its entire roof
was destroyed. A second thunderstorm moved into Amarillo from the
northwest at about 9:45 pm also exhibiting strong rotation and brief
hook echos on the radar reflectivity data. A tornado warning was
issued for this storm at 9:30 pm and while no tornados were observed
with the storm, it did bring strong straight line winds with 68
mph being recorded at Rick Husband airport.
Amarillo was not the only city affected by severe thunderstorms
on this day. Many severe thunderstorms developed across the Texas
panhandle affecting Stinnett, Canyon, Romero, Sunray, Stratford,
Boys Ranch, Channing, Darrouzett, Follett, Pampa, Lefors, Groom,
Clarendon, and Palo Duro State Park. I also want to mention that
the town of Gruver was hit hard by hail that broke many windows
on the evening of Friday, June 18th. While it is easy to be upset
over the damage that these storms have caused, let's also be thankful
that the damage was not much worse, because looking at the radar
imagery from that evening it is still hard for me to believe that
a tornado did not move across the city of Amarillo. Thanks to all
the spotters who kept an eye on the storms as well as everyone who
phoned in their weather reports. Our job is made much easier due
to your hard work.
For more information on this event visit our website at http://www.srh.noaa.gov/ama/html/Jun212004/Album/index.htm
|