44 Doppler-derived thermodynamic structure of miniature supercells observed in the outer rainbands of Hurricanes Ivan (2004) and Gustav (2008)

Monday, 26 September 2011
Grand Ballroom (William Penn Hotel)
Matthew D. Eastin, University of North Carolina, Charlotte, NC

Numerous recent studies have shown that the rotational environment of a tropical cyclone favors the development of intense convective cells with cyclonic vorticity and vertical velocity maxima collocated. In the TC inner core, such entities have been labeled as vortical hot towers (VHTs), have been shown to intensify the system through upscale energy transfer as the VHTs merge and become axisymmetrized by the parent vortex. However, in the TC outer core, such entities are often labeled as miniature supercells, and often spawn tornado outbreaks as their parent outer rainbands move onshore. Many questions remain regarding the structure, evolution, and impact of these miniature supercells, particularly since the environment of such supercells is vastly different than their mid-latitude counterparts.

The objective of this study is to expand upon previous dual-Doppler analyses of intense convective cells (some of which were supercells) in the outer rainbands of Hurricanes Ivan (2004) and Gustav (2008) by using the Doppler-derived kinematic fields to solve for the associated thermodynamic structure using standard techniques. Our goal is to clarify the updraft forcing and its relation to the collocated vertical vorticity maximum. An extensive observational dataset composed primarily of airborne NOAA WP-3D Doppler radar data and then supplemented with flight-level, dropsonde, rawinsonde, buoy, and WSR-88D radar data is used. A synopsis of our preliminary results and their comparison with previous studies will be presented at the conference.

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