12A.5 Topographic and geographical influences on regional severe tornado maxima

Thursday, 27 January 2011: 9:30 AM
613/614 (Washington State Convention Center)
Grayum Vickers, Florida State University, Tallahassee, FL; and J. Cossuth

There are two dominant modes of tornadogenesis: supercell/mesocyclone related and non-supercell related. The strongest tornadoes tend to form from mesocyclones in supercells, and are among the most damaging and deadly meteorological phenomena. Non-supercell modes of genesis, such as by low-level wind shear, generally produce weaker varieties of tornadic activity (gustnadoes, landspouts, etc.), and have a smaller societal impact. By isolating cases of intense tornadoes (F3 and higher), the mesocyclone mechanism of tornadogenesis is highlighted and a climatology of severe tornadic activity is defined, revealing several local “tornado alleys” world-wide.

Building on previous work by Broyles et al. (2003) and Feuerstein et al. (2005), which address the existence of said local “tornado alleys”, this work inter-compares different “tornado alleys” and attempts to explain the reasons for their existence. Using tornado reports from around the world, topographic and geographical mechanisms are shown to influence the likelihood of tornado formation in specific regions. Areas of intense tornadic activity are commonly downstream of higher elevation and in close proximity to a significant body of water. In addition, the meteorological profile of an archetypal mesocyclone tornado is created from composited reanalysis data. Such composites are used to bolster the importance of orography and geography in aiding tornadogenesis, as well as identify specialized meteorological parameters that contribute to severe tornado formation in different regions.

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