Extended Abstract (92K)6.1
Development of an enhanced Fujita Scale for estimating tornado intensity
James R. McDonald, Texas Tech Univ., Lubbock, TX
Both the severe local storms and engineering communities have long recognized limitations to the Fujita Scale as a measure of tornado intensity. The Fujita Scale does not recognize differences in construction quality, it is difficult to apply without clear-cut damage indicators, it is subject to bias of the person making the assessment and tends to overestimate wind speeds in the F3, F4 and F5 categories.
Recognizing the need to make improvements to the Fujita Scale, the Wind Science and Engineering Center at Texas Tech University (TTU) volunteered to take on the task. A steering committee was appointed to develop a strategy and organize a forum of interested users. The objective of the forum was to ultimately recommend a new or modified Fujita Scale. The objective also included a strategy for achieving a general consensus among the users and interested parties. In addition to some lively discussions, the 25 attendees submitted individual comments and suggestions that were incorporated in a forum report.
TTU personnel were to propose modified wind speeds and additional damage descriptions. In carrying out the assignment, it became apparent that better correlations between damage indicators and wind speeds were needed before the Fujita Scale could be effectively modified. After several unsuccessful attempts at damage versus wind speed, TTU explored the concept of expert elicitation, which has been successfully used in estimating earthquake parameters that cannot be measured directly. The Senior Seismic Hazard Analysis Committee (SSHAC) published a formal expert elicitation procedure.
A panel of experts came together and initiated the SSHAC protocol. The results are currently being assembled and analyzed. The expert elicitation data will then be used to formulate new wind speed ranges and damage descriptions for review and comment.
Forum members felt strongly that the current tornado database should be preserved; the assessment methodology should lead to more consistent assignment of Fujita Scale categories and that the Fujita Scale assessments should be adaptable to some type of exert system in the future. The forum participants also agreed that the activities should receive widespread publicity through workshops and symposiums at engineering and meteorological professional meetings.
Session 6, Damage Assessment and Wind Speeds
Tuesday, 13 August 2002, 1:30 PM-3:00 PM
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