Corrections in Tornado Counts, F-scale Intensity, and Path Width for Assessing the Destructive Potential of Significant Tornadoes

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Tuesday, 4 February 2014: 1:30 PM
Room C102 (The Georgia World Congress Center )
Samuel J. Childs, Purdue University, West Lafayette, IN; and E. M. Agee

Issues related to biases in archived tornado records (1950-2012) have been addressed, which include the following: a) rationale for removal of the years 1950-1952, b) identification of inconsistencies in F0, F1, and F2 counts based on both the beginning of the F-scale and the implementation of Doppler radar, c) overestimation of backward extrapolated F-scale intensity, and d) change in path width reporting from mean width (1953-1994) to maximum width (1995-2012). Unique corrections to these inconsistencies offer a more homogeneous tornado record, as well as the opportunity to evaluate climatological trends in tornado activity. Significant tornadoes are recognized as the most destructive and deadly, and their kinetic energy fields have been determined, which show no appreciable trend through time. The median wind speed (Vmed) of each respective EF-scale from 1953-2012 (modified for 1953-1973 to address overestimated intensities) was used to calculate kinetic energy, since actual maximum winds were not available. The annual mean maximum path width (Wmax) from 1953-2012 (adjusted upward from 1953-1994), however, displays an increasing trend, with a pronounced Lower Threshold for all years in the record. Also, the EF-scale median wind speeds are highly correlated with Wmax. The quantity (Vmed Wmax)2, defined as the Destructive Potential of a Tornado (DPT), suggests increasing extreme events through time, with the three largest values in the 60-year record being 2007, 2008, and 2011.