Introduction

Allison in Texas, 5 – 9 June 2001

Tropical Storm Allison came ashore near Galveston during the evening of 5 June 2001 and finally exited back into the Gulf of Mexico about halfway between Corpus Christi and Houston, TX. The flooding it produced resulted in 22 deaths in the Houston area alone, some the result of rapidly rising waters overtaking stalled cars on local freeways. This was in spite of timely watches and warnings for flash flooding by the local NWS forecast office. As much as 36" of rain was reported to the northeast of downtown Houston over the 5-day period ending 3 PM on 9 June! Click the Display Graphic button below to see the rainfall graphic from the Houston Chronicle.

 Rainfall in Houston, TX area, 5 – 9 June 2001

Allison was an unusual storm throughout its 13-day history. Its development, track, precipitation production, and circulation maintenance during the first few days of its existence were marked by

• Sudden and unexpected development in the northwestern Gulf of Mexico as unfavorable westerly wind shear aloft weakened
• Ambiguity over whether it was actually a tropical storm or a hybrid system with tropical and extratropical characteristics
  
  
• The storm reportedly had a tilt to the north with height as it moved ashore. Tilt of circulations with height is associated with extratropical (baroclinic) systems, rather than tropical systems.
• The highest winds were some distance from the center of lowest pressure, and only in those relatively distant locations qualified as tropical storm strength.
  
  
• Maintenance of strength after making landfall on the night of 5 June

• Its erratic track after making landfall
  
  
  • The storm performed a pair of loops between 6 and 10 June; one east of Waco, TX on the 6^th and 7^th, the other larger loop closed as the storm moved east-southeast of Victoria, TX into the Gulf of Mexico and intersected its initial northbound track early on the 10^th.

Credits

By Dr. Bill Bua, UCAR/COMET

Thanks to:

• Mike Eckert for providing text and graphics discussions for HPC QPF
• Stephen Jascourt for helpful discussions and developing the HTML format
• Eric Rogers for assistance in obtaining Eta-22 and Eta-10 data