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Texas Tech Researchers Help Develop New Tornado Ratings Scale

Posted on: Saturday, 4 February 2006, 06:00 CST

By Carlos Bergfeld

By Carlos Bergfeld
Daily Toreador ( Texas Tech )

(U-WIRE) LUBBOCK, Texas -- Ted Fujita devoted his academic research to studying winds and tornadoes, which led to the development in 1971 of the tornado-rating scale that bears his name. Still used today, the Fujita Scale now has a successor slated for 2007, perhaps fittingly developed at Texas Tech University, which now holds much of his original work. The National Weather Service announced Thursday it will put into practice the Enhanced Fujita Scale, developed in part by Tech researchers, by February 2007 as its main method in measuring the intensity of tornadoes. The Enhanced Fujita Scale will be more consistent than the standard Fujita Scale through examining more and varied damage indicators. "In the past, in order to assign a scale, you only looked at one or two damages, the most severe damage," said Kishor Mehta, professor of civil engineering and former director of the Wind Science and Engineering Research Center. "At times, it's difficult to use -- it doesn't have a description of damage in detail." As one of two researchers from Tech who worked on the project, Mehta said the Fujita Scale was effective in its time, although the new scale will produce more consistent results. The Enhanced Fujita Scale builds on the Fujita Scale, as both are based on assigning a numbered rating on a six-point scale to tornadic events derived from an analysis of the damage after the event. The project to make the new scale began in 2001, when Mehta and Jim McDonald of Tech held a forum with other scientists to decide how the scale redesign should be implemented. "We were wanting to involve as many people as we could who had an interest in the Fujita scale," said McDonald, a retired chairman of the civil engineering department and Mehta's partner on the project. The two turned to experts in the field to collaborate on the endeavor in more ways than as consults for the preparatory forum, however. McDonald used a process he called "expert elicitation" to make the scale more reliable during its development. Experts on a particular topic would be asked to give estimated wind speeds for certain types of damage. These results were compiled into what became the criteria for judging which wind speeds would result in certain ratings. McDonald's main problem with the Fujita Scale concerned the high wind speeds needed to garner the highest ratings. On the standard Fujita Scale, wind speeds would need to be from 260 to 318 miles per hour for an event to be classified as an F5 tornado. On the Enhanced Fujita Scale, any wind speeds of more than 200 miles per hour make an event an EF5 tornado. The team submitted the project to the National Weather Service in June 2004, but they would not know of the scale's acceptance until late last year when the Weather Service contacted the researchers with details. "It's a major item to change it," Mehta said. "You don't want to change it unless everyone feels comfortable with what should be done." Fujita's original work, while at the University of Chicago, can be viewed in Tech's Southwest Collection, which received much of Fujita's work last summer. The Fujita Scale will have been used for 36 years when it is retired in 2007, and McDonald hopes the Enhanced Fujita Scale can be similarly successful. "It's developed in such a way that we can make refinements to it," he said. Current technologies still do not allow scientists to measure the high wind speeds of tornadic events directly, which is why both Fujita scales base their ratings on a storm's aftermath. However, technology has been catching up. McDonald said he believes the new scale will be the last scale necessary until direct wind measurements are possible. Mehta and McDonald will work closely with the National Weather Service to advise them on use of the scale until its implementation begins in 2007.

(C) 2006 Daily Toreador via U-WIRE

Source: U-WIRE

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