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Research Projects » Tornado Outbreak (October 1997)
...TORNADO...
Outbreak Over Southeast Texas
(October 23, 1997)
INTRODUCTION
A widespread severe weather event developed across Southeast Texas on Thursday October 23, 1997 in which numerous tornadoes...funnel clouds...gusty
winds and large hail were reported. There were a number of interesting meteorological parameters that came together to produce this severe weather episode.
SYNOPSIS
On the large scale...a cold front had pushed through Southeast Texas on Tuesday evening October 21 and became stationary across deep south Texas between Corpus
Christi and Brownsville. In the upper levels of the atmosphere...the polar jet was nearly zonal for the western two thirds of the nation with a deepening trough
developing over the eastern third. A slow moving upper level low pressure system and associated low pressure trough dominated the western half of the sub-tropical
jetstream. A confluent zone developed over the eastern third of the nation as the polar and sub-tropical jetstream merged. The cold front over deep south Texas
began to return north as a warm front Wednesday night. The upper level low in the sub-tropical jetstream was ejected eastward Wednesday night and Thursday.
As this feature moved east...the polar jetstream curved to the northeast while the subtropical jetstream became zonal. This created a large area of diffluence
aloft over southeast Texas and southwest Louisiana.
By Thursday morning, the warm front had entered Southeast Texas. Surface dewpoints were rising into the lower and middle 60s and surface winds were
becoming southeast while just off the surface...a southerly low level jet of 30 to 40 knots had developed. By mid-Thursday morning a 110 to 120 knot wind speed
maximum at 200 mb embedded in the subtropical jetstream approached south Texas putting southeast Texas in the favorable left front quadrant. An intrusion of dry
air at 500 mb further destabilized the atmosphere producing incredibly unstable lapse rates. Data from LCH and CRP soundings and the KHGX VWP indicated
tremendous turning in the atmosphere as southeast surface winds became south at 1000 feet...southwest between 2000 and 3000 feet and west at
5000 feet. Model helicity values were progged to exceed 400 m2/s2 between 12z Thursday and 00z Friday. As the upper level wind
speed maximum approached south Texas...showers and thunderstorms developed rapidly...with some of the storms becoming severe.
PRODUCTS
SUMMARY
This event saw a total of 11 tornadoes touch down in Southeast Texas. These tornadoes did cause extensive property damage in some communities. The average lead
time between the time the tornado warning was issued and the tornado touched down was 24 minutes. The lead time ranged from 4 minutes to 58 minutes. There
were no deaths from any of these storms and only one injury reported. Actual damage amounts are still being collected, but totals will likely approach the 2 to 3 million
dollar amount.
For more information and details concerning this event, please refer to the items listed below.
Prepared by NWSO Houston/Galveston Staff
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