Mid-tropospheric patterns and historic tornado outbreaks

Most tornado-related fatalities in the United States result from tornado outbreaks [1]. Major tornado outbreaks are particularly dangerous because they consist of multiple, often violent, long-track tornadoes and, therefore, are more likely to affect populated areas [2]. Synoptics-scale environmental conditions that support the development of those outbreaks can be studied in terms of atmospheric patterns occurring prior to initiation. Accordingly, this research identifies large-scale atmospheric patterns associated with tornado outbreaks using T-mode principal component analysis (PCA) on data matrix comprised of geopotential height fields at 500 hPa over a 779 point grid from dates with tornado outbreaks for the years 1950 - 2014, utilizing kernel density estimation on events with at least 7 tornadoes of magnitude EF2 or higher. This study will present resulting atmospheric patterns and will focus on their importance in tornado outbreak diagnostics and risk mitigation efforts.

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1) Schneider, R. S., A. R. Dean, S. J. Weiss, and P. D. Bothwell, 2006: Analysis of estimated environments for 2004 and 2005 severe convective storm reports. Preprints, 23rd Conf. on Severe Local Storms, St. Louis, MO, Amer. Meteor. Soc., 3.5.

2) Brooks, H.E., 2004: On the relationship of tornado path length and width to intensity. Weather Forecasting 19, 310–319.