160 Cold Pool Horizontal Streamwise Vorticity During Tornadogenesis and Maintenance in a Simulated Supercell Thunderstorm

Thursday, 25 October 2018
Stowe & Atrium rooms (Stoweflake Mountain Resort )
Kelton T. Halbert, Univ. of Wisconsin–Madison/CIMSS, Madison, WI; and L. Orf and A. W. Dixon

Recent cloud model simulations of a long-track, EF-5 tornado at high temporal and spatial resolutions (isotropic 30 meter grid spacing; data saved to disk every 1/6s) have provided an opportunity to investigate the processes that lead to the development and maintenance of a violent tornado that persists for nearly 2 hours within the simulation. Of particular interest are the budgets associated with vorticity and the mechanisms that generate and maintain a long-lived mesocyclone and tornado in the simulation. Qualitative analysis of the simulation has suggested that horizontal vorticity in the forward-flank downdraft cold pool is critical for the formation and maintenance of the violent tornado, evidenced by the persistent presence of streamwise horizontal vortex tubes that interact with the low-level updraft prior to tornadogenesis and with the tornado during the maintenance phase, warranting a more rigorous investigation. This study uses fluid parcel trajectory analysis to track of the vorticity budget of parcels originating in the cold pool before, during, and after tornadogenesis, to quantify the role of horizontal vorticity on the low level mesocyclone and tornado, and to provide insight into the processes that are generating this streamwise horizontal vorticity in the lowest 500 meters of the simulation.
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