161 Observed Relationship between Tornado EF Rating and Pre-Tornadic Mesocyclone Width

Thursday, 25 October 2018
Stowe & Atrium rooms (Stoweflake Mountain Resort )
Michael Sessa, Valparaiso Univ., Valparaiso, IN; and R. J. Trapp and J. Einbinder

Trapp et al. (2017, JAS) used idealized model simulations of supercell thunderstorms to demonstrate support of their hypothesis that wide, intense tornadoes should form more readily out of wide, rotating updrafts. The next step in this research is to use observational data to test the generality of the hypothesis, especially to tornado-bearing convective morphologies such as QLCSs, and within environments such as those found in the southeastern U.S. during boreal spring and autumn. We have begun to assemble a new radar dataset that focuses explicitly on the pre-tornadic updraft width and mesocyclone diameter/intensity: the pre-tornadic focus allows us to eliminate the effects of the tornado itself on the mesocyclone characteristics. Thus far, we have used GR2Analyst to manually analyze 50 tornadic events during the period 30 September 2013 to 31 December 2017. The corresponding tornadoes had damage (EF) ratings ranging from EF0 to EF4, and all were within 100 km of a WSR-88D. A key finding thus far is that the linear regression between the EF rating of the tornado and the mean, pre-tornadic width of the mesocyclone yields a coefficient of determination (R2) value of 0.58. This encouraging relationship will be added to the others currently under exploration, including ones involving environmental parameters.
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