Climatology of cool season severe thunderstorms in the east-central United States, 1995-2002

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Smith, Bryan T.
Zimmermann, Petra A.
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Thesis (M.S.)
Department of Geography
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While the spring and summer months are typically the severe weather climatological peak for the East-Central United States, severe thunderstorms and deadly regional tornado outbreaks can occur during the cool season months (e.g., October-March). In an effort to better document and improve operational forecasting of these events, this study focuses on cool season severe thunderstorms in the Ohio and Tennessee Valleys during the 1995-2002 cool seasons.Most severe thunderstorm and tornado events in the East-Central United States during the cool season are characterized by a high frequency of wind reports compared to hail and tornado reports. All severe report classes (i.e. tornadoes, hail, and wind) displayed a frequency tendency to remain high in the late evening and overnight hours. Additionally, it was found that tornado occurrence typically came in the form of a tornado outbreak. Additionally, when tornadoes did occur, they were found to be statistically more intense than tornadoes outside of the EC region during the same period. It is also concluded tornadoes favor the southern half of the region, whereas hail and wind reports tend to favor the southern two thirds of the region. In examination of cool season supercell characteristics, supercells favors a west-southwest to east-northeast mean motion around 45 mph. The relationship of only 11 percent between the distances of supercell tornado paths to tornadic supercell paths is an operationally important discovery. Knowing on average, how long a cool season supercell tornado is on the ground with respect to the parent supercell can aid operational warning decisions.