Session 8B.3 Damage survey and deduction of vortex structure of the Greensburg, KS tornado

Tuesday, 28 October 2008: 2:00 PM
South Ballroom (Hilton DeSoto)
Timothy P. Marshall, Haag Engineering Co., Irving, TX; and D. McCarthy, J. G. LaDue, J. Wurman, C. R. Alexander, P. Robinson, and K. A. Kosiba

Presentation PDF (1.4 MB)

On May 4, 2007, a large and violent tornado struck the town of Greensburg, Kansas. Approximately 95 percent of the town was destroyed including more than 500 homes and businesses. Ten people were killed. Detailed ground and aerial damage surveys were conducted by two independent teams and a consensus damage intensity and implied peak wind speed and direction map is being produced. Peak implied wind speeds were 92 m/s on the east side of the tornado path, making this the first EF-5 rated tornado using the new EF-Scale adopted by the National Weather Service. Using the damage-based peak wind speed map and a DOW-radar-based model of of low-level winds based on direct observations of other large violent tornadoes, including Mulhall (1999), Seward (2007), and Alison (1995), various structural parameters of the Greensburg tornado are deduced. These include Peak ground relative wind speed, peak tangential wind speed, diameter of core flow region, and the radial dependence of tangential winds both inside and outside the core flow region. Using this technique, the structure, size, and intensity of the Greensburg tornado can be compared objectively to other large and violent tornadoes.
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