P2.133 The 8 May 2009 "super derecho": A land-hurricane?

Thursday, 13 May 2010
Arizona Ballroom 7 (JW MArriott Starr Pass Resort)
Morris L. Weisman, NCAR, Boulder, CO ; and C. Evans and L. Bosart

During the morning of 8 May, 2009, a large bow echo system developed over Kansas and proceeded eastward, producing an extensive swath of severe wind damage from eastern Kansas through southern Illinois over an 8 hour period. During its most intense phase, the bow echo occluded, producing a warm-core eye-like structure similar in many respects to tropical cyclones. Indeed, much of the wind damage with this system was associated with an intense ( 10 mb) mesolow located at the tip of the occlusion, well behind the leading gust front. The circulation associated with this mesolow extended about 80 km across, and, although strongest at low-to-mid levels ( 100 kts at 850 mb), extended up to 10 km as a vertically coherent feature. No significant predecessor vorticity feature aloft could be identified in association with this system. This convective system was forecast in realtime 24 h in advance with the WRF-ARW model, using a 3 km horizontal grid interval, accurately reproducing the observed occluded eye-like structure and accompanying intense, deep mesoslow.This forecast allows for an unprecedented analysis of the structure and evolution of such a unique convectively produced mesoscale vortex, perhaps offering a tantalizing example of how meso-convective processes in the presence of low-level vertical wind shear could potentially contribute to tropical storm genesis. Preliminary results of this analysis will be presented, along with comparisons to the similar recent study of the re-intensification of Tropical Storm Erin over Oklahoma in 2007.
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