Thursday, 13 May 2010
Arizona Ballroom 7 (JW MArriott Starr Pass Resort)
Recent numerical simulations and observations of vortical hot towers (VHTs) have documented their role in tropical cyclone genesis. This study uses dual-Doppler wind analyses to document VHTs in the eyewall of Hurricane Guillermo (1997) during its rapid intensification. An initial census of all strong asymmetric updrafts reveals that VHTs (which also contain significant perturbation vertical vorticity) represent ~15% of the population, occupy only a small fraction (~2%) of the total eyewall area, but accomplish a significant fraction (10-15%) of the total upward mass transport. In Guillermo, the vast majority of VHT are located in the left-of shear and upshear quadrants. The composite structure of the 16 observed VHTs was examined. Of particular note was strong, asymmetric, low-level outflow from the eye into the base of the composite VHT, suggesting that a portion of the air rising through an eyewall VHT originates in the eye. If this low-level air is locally buoyant, the eye may serve as the primary buoyancy source for a typical eyewall VHT. A synopsis of our results and their comparison with previous numerical studies will be presented at the conference.
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