This storm initially formed just south
of Childress. It then either (a) translated; and/or, (b) was associated
with new development on the south flank so that it discretely
propogated southeastward across the western portions of the Abilene
area and then southeastward. We chased the storm from north of
Sweetwater until sunset when it was about 100 miles southeast
of San Angelo. During this life cycle, we observed one significant
tornado in Sweetwater (see below and on next page) and one other
possible brief tornado touchdown (unphotographed) near Ballinger.
In this picture (and one on the next page), the outflow shelf was magnificent as the storm wound down just before sunset. Lightning had started a prarie fire and the smoke from this was being ingested into the storm. We were concerned that this column might be misidentified as a tornado.
On the morning of May 31, 1995, relatively moist air ahead of a dryline extending from eastern New Mexico southward through extreme west Texas was in place across west and north-central Texas. Surface dewpoints ranged from near 60F at Midland to the mid 60's near Fort Worth. The surface chart also showed a weak low in west Texas with a quasi-stationary frontal boundary extending eastward across the southern Texas Panhandle and connecting to a cold front along the Red River Valley. Check out our subsynoptic analysis. (Dashed lines are isodrosotherms, solid contours isobars (millibars), solid arrows (subjectively-drawn streamlines).
This view is towards the west-northwest.
Sweetwater is approximately 10 km away. 4" hail, straightline
winds in excess of 50 knots raked Sweetwater at this time. The
cloud structure was roiled, had a large "bear cage"
appearance over Sweetwater. Rain and hail wrapped around the west
side of the updraft several times during this time but never completely
encircled the updraft.
The hodograph was characterized pronounced veer of the wind and wind shear vectors from the surface through 3km. Surface winds were generally 10 knots or less across west and north Texas although some reports of 15 knot winds were evident. Midlevel winds were at the low end of the spectrum (30 knots at 500 mb and 20 knots at 700 mb) and supported only weak to moderate storm-relative flow. Project afternoon CAPE was in the 3500 J/kg range. The 12Z MAF sounding that a well-mixed nearly-dry adiabatic layer surmounts a 100 mb thick moist layer.
The midtropospheric flow was initially westerly over this portion of Texas but became west-northwesterly as a weak shortwave embedded in the flow progessed eastward across the Texas Panhandle. This short wave was associated with weak cold advection.
The surface cold front was likewise in the
Texas Panhandle and had advanced to a Lubbock-Childress-Altus
line by Noon CDT. Surface pressure falls ahead of the mid-tropospheric
short wave trough axis and ahead of the surface cold front were
inducing an eastward surge of the dryline, which passed Midland
at around 11AM CDT. Thunderstorms had developed ahead of the dryline
southwest of Childress by mid-morning. At about 1:30 PM CDT, the
dryline and cold front intersection was between Lamesa and Colorado
City. At this time, surface flow between Abilene and Sweetwater
and backed to easterly and had increased to sustained 20 knots.
The earlier thunderstorm had progessed due southward and was near
this location when intersection occurred. The thunderstorm developed
a backsheared anvil and mesocyclone at around this time when it
was just north of Sweetwater, TX.
Click here to
see more pictures of this storm as it passed through Sweetwater
(N.B., images are interlaced but loading may take some time--300
kilobytes). There are two additional pages.
