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Research Projects » Tornado Outbreak (November 2003)
Southeast Texas
November 17, 2003
Tornado Outbreak
INTRODUCTION
A series of tornadic thunderstorms ravaged much of southeast Texas Monday and
Monday night, November 17, 2003. The storms developed over parts of Wharton and Matagorda
counties shortly after sunrise with the first confirmed tornado occurring just east of El Campo around
9:00 am. This summary will describe the parameters in which led to the development of these storms
and a summary of rainfall data and flooding reports. Our thanks to Emergency Managers, media, storm
spotters and the public for the timely severe weather reports.
Prepared by WFO Houston/Galveston Staff
SYNOPSIS
A strong 500mb upper level trough of low pressure over the western U.S. was moving from west to
east across the southern plains. The polar jetstream associated with the 500 millibar trough surged into
west Texas and then curved sharply to the northeast into the Central Plains. The sub-tropical jetstream
was oriented west to east across Deep South Texas. The jetstream pattern is strongly divergent and
is frequently an ingredient in severe weather. Low level moisture had been increasing and was about
200 percent of normal by 6 AM Monday morning. Vertical wind profiles also showed a great deal of
wind shear or low level turning of the winds with height. This turning was particularly pronounced in
the lowest 2000 feet of the atmosphere. In addition, wind speeds increased rapidly with height. Wind
speed and directional shear are two important parameters necessary for tornadic thunderstorms. Lastly,
a weak low level boundary was aligned from southwest to northeast generally along the U.S. Highway
59 corridor. This provided a focus for thunderstorm development. This feature was nearly stationary and
thunderstorms repeatedly developed and moved along this boundary. The axis of heaviest rain was
coincident with this nearly stationary boundary.
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