PRINT THIS PAGE | E-MAIL THIS PAGE

Monday, October 27, 1997

Jarrell twister didn't fit patterns

AUSTIN (AP) - A scientist studying the tornado that devastated Jarrell last May says the twister had several unusual aspects that contributed to its deadliness.

The May 27 storm killed 27 people in the central Texas town, leaving nothing behind of several homes but their concrete foundations.

Baylor University meteorology professor Don Greene spent six days studying the tornado's path. It was his first opportunity to investigate an F5, the rarest and most powerful of tornadoes.

He plans to present his findings to the Texas Academy of Sciences at a meeting next spring.

Only one in 200 tornadoes is powerful enough to be classified as F5, with winds blowing at least 261 mph - strong enough to carry away sturdy frame houses, turn cars into missiles and suck trees out of the ground.

Greene discovered other oddities:

- For such a powerful tornado, the Jarrell twister didn't travel far - about five miles.

"When an F5 does form, the (thunderstorm) is usually so large that the tornado will be long-lasting, covering 50 miles or better," Greene said.

- The tornado took 11 to 18 minutes to travel one mile through the Jarrell neighborhood, a remarkably slow speed.

"The average speed of a tornado is 30 mph, and sometimes they'll go 60 mph or better. But this one, you're only talking about going 4 mph," Greene said.

- The tornado traveled southwest - the opposite direction of the vast majority of U.S. tornadoes, which typically travel northeast.

"Because this one was going 180 degrees in the wrong direction, that could explain why it had such a slow velocity," Greene said, adding that the southwest-bound storm had to fight against upper-level winds moving east.

Greene's studies also revealed that many of the Jarrell homes were blown down by winds preceding the funnel, leaving residents exposed "to the full force of the tornado."

The storm offered a unique opportunity to study debris patterns left by an F5 tornado because, outside of a few farmhouses a mile to the north, every piece of debris originated in the Jarrell neighborhood.

Studying the debris can reveal details of the tornado's "transport mechanism," or its carrying capacity, Greene said.

The most massive objects - appliances, cars and engines - remained in the path of destruction and were deposited in three drop zones near the subdivision. These were moved in a process called saltation, repeatedly bounced along the ground at the funnel's base, Greene said. Send a Letter to the Editor about This Story | Start or Join A Discussion about This Story
Send the URL (Address) of This Story to A Friend: