F0 tornado in Harris County, Texas

Tornado traveled from Galveston County across Clear Creek 1/4 mile into Harris County. Tree damage in community park on east side of creek.

A total of 24 tornadoes touched down during this 15 hour period of severe weather in southeastern Texas on November 17, 2003. In addition to these tornadoes, a major flood developed over Harris and surrounding counties during the middle of this tornadic outbreak. Over 300 homes, along with hundreds of vehicles, were flooded.These tornadic 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. Strong 500mb upper level troughing over the western U.S. moved from west to east across the Southern Plains. The polar jet stream associated with this 500 millibar trough surged into west Texas and then curved sharply northeastward into the Central Plains. The sub-tropical jet stream was oriented west to east across deep southern Texas. This jet stream pattern was the impetus to strong lower level convergence due to the enhanced upper level divergence. Low level moisture had substantially increased and was about 200 percent of normal by 6 AM. Vertical wind profiles also showed a great deal of low level wind shear with the greatest shear occurring in the lowest 2000 feet. In addition, these veering wind speeds rapidly increased with height. A focus for the thunderstorm development was provided by a weak low level boundary which was aligned southwest to northeast, or generally along the U.S. Highway 59 corridor. This feature was nearly-stationary and thunderstorms repeatedly developed and moved along this boundary. The axis of heaviest rain was coincident with this boundary.