Sunday, 22 January 2012
Shear and Buoyancy Parameters for California Tornadoes From 1951—2011
Hall E (New Orleans Convention Center )
The wind shear and buoyancy profiles associated with tornadoes in the Great Plains have been well documented for many years. The current understanding of mesocyclone-induced tornadogenesis now rests firmly on an ingredients-based approach involving thoughtful evaluation of these profiles. Previous studies of California tornadoes have shown, as expected, that the wind shear profiles associated with them, especially the stronger F1 and F2 tornadoes, are consistent with those wind shear profiles of supercells and tornadoes found in the Great Plains. However, these earlier studies had included only a fraction of the tornado events in California and therefore evaluated a very limited data set. In the present study, buoyancy and wind shear profiles for all the California tornado events from 1951—2010 were examined. The shear and buoyancy profiles near each tornado event were estimated on the basis of manually produced proximity soundings (by subjective alteration of the nearest radiosonde observation). Since objectively derived soundings, for example, from the RUC, have been available only in the last decade, the authors chose to maintain a consistent approach for every case. Future work will involve comparing the objectively produced proximity soundings for cases in the last decade to those produced by the method outlined by the authors in the presentation. The analysis of the proximity sounding data gives the expected result that the shear and buoyancy profiles of the stronger F1. F2 and F3 tornadoes in California were comparable to those associated with supercellular tornado events in the Great Plains and suggest that these events in California occurred from storms that were supercells. Since WSR-88D radar information is only available for California events since 1995 or so, the results must be regarded as inferential. However, it is noteworthy that the same range of ingredients that combine to produce supercell tornadoes elsewhere in the country also occur in California. While this result is not earthshaking to the national severe storms community, it is important to point out that there are still vestiges of the “…California tornadoes are cold core, weak and short lived…” misconception in the operational community in California to this day.
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