Storm Report - By the staff at WFO Corpus Christi
General Weather Summary
On Thursday, October 27, 2005, a weak surface boundary extending from near Uvalde to Cotulla to Kingsville, separated warm moist air over the Rio Grande plains from drier and slightly cooler air across southeast Texas. In addition, the base of an upper level trough moved across south-central Texas Thursday afternoon. This feature provided some large scale lift and ushered colder mid and upper level air across the region, which destabilized the atmosphere as surface temperatures rose into the upper 70s and low 80s. The surface high pressure center to the northeast provided a moderate easterly flow near the surface which quickly turned southeast to south above the surface. In addition, modest westerlies existed in the mid and upper levels of the atmosphere. This vertical wind shear (changing of wind direction with height) together with the modestly unstable atmosphere provided an environment favorable for rotating thunderstorms. The Storm Prediction Center issued a severe weather outlook in the afternoon which highlighted possibility of locally damaging winds and hail with a strong storm or two. During the afternoon scattered thunderstorms began to develop in the warm, unstable airmass across the Rio Grande plains and deep south Texas. A few thunderstorms, which developed along the weak surface boundary, gained strength and became severe as they moved southeast along the boundary.
Severe Weather Event & Impacts
The event began as a strong storm developed near Zavala/Frio Counties in the western hill country. This storm quickly became severe as it crossed into La Salle County, gaining supercell characteristics as it traveled along the surface boundary across La Salle and southwest McMullen counties. Reports of dime to penny size hail and 60 mph wind gusts were received by storm spotters just south of Dilley in northern La Salle County. No storm reports were received in McMullen County, likely because of the lack of population and roadways through the area where the severe storm tracked.
The storm tracked through southwestern McMullen and northern Duval Counties, maintaining its strength while exhibiting strong convergence in the middle portions of the storm (MARC signature) at times. Another storm pulsed up across north-central Jim Wells County before weakening southeast of Alice. Outflow from this storm, as well as moderate to strong east to northeast flow across the Coastal Bend and southeast Rio Grande Plains, may have contributed to an enhanced area of wind shear across Duval County. As the La Salle/McMullen supercell thunderstorm moved into this area across Duval County, the thunderstorm circulation steadily deepened and strengthened. Doppler radar showed and a reflectivity notch developing right along the above mentioned boundary associated with the increased storm rotation. A Tornado Vortex Signature developed near this notch prompting a tornado warning at 625 PM. Prior to the tornado warning, severe thunderstorm warnings were present through the life of this storm due to strong hail signatures and severe straight line wind indicators as seen on Doppler radar. The hail photo above was taken on October 28th, approximately 20 hours after the event.
NWS Damage Survey
A National Weather Service storm survey team toured Duval and Jim Wells counties and concluded the damage was largely a result of straight line winds from a long track supercell thunderstorm. However, it cannot be ruled out that an isolated tornado was embedded in the storm. Wind speeds were estimated to range from 80 to 100 mph which is equivalent to an F1 tornado on the Fujita damage scale. The damage swath, which was approximately 4-5 miles in width and over 40 miles in length, stretched from just east of Freer to near Premont.
Broken windows and roof shingle damage on all properties was observed on the northwest side of structures, which indicates straight line wind damage and the wind blew from the northwest to the southeast. American Electric Power (AEP) crews on the scene reported that roughtly 100 power poles were knocked down. The NWS team assessed that all poles were blown in the downwind direction to the southeast.
Visible damage began near highway 44 and FM 3196 (approximately 2 miles northeast of Freer) where roughtly half a dozen power poles were knocked down. The damage continued in the community of Rosita in which one house experienced minor damage. Hail was also reported up to 4 inches in depth. Photo's of the hail in this web survey were taken approximately 20 hours after the event. The NWS storm survey team also observed indications of Flash flooding on Rosita Creek.
The storm appeared to strengthen as it approached the northeast side of Benavides and the town of San Jose. Two mobile homes were destroyed and tree limbs were broken with all damage lying in a southeast direction. A total of fifteen homes were damaged in San Jose with window and roof damage on the northwest side, which again indicates the wind blew from the northwest to the southeast.
Click on red boxes to view impacts from storm
Just southeast of San Jose, near the intersection of Farm Road 2295 and 1329 and extending south all the way to Rios, tree limbs and power poles were broken and lying in a southeast direction. An empty grain silo was also destroyed and a newly framed home was blown off its foundation.
In extreme southwest Jim Wells county near the intersection of County Road 428 and 716, a large empty grain silo was destroyed and lying in the middle of the roadway. Power poles were knocked down, 5 homes were damaged, and 1 garage was completely destroyed. Again all the visible damage was lying in a southeast direction.
Eye witness reports indicate that nickel to quarter sized hail covered the ground up 4 to 6 inches deep along the entire storm track.