15A.6 Internal storm dynamical processes leading to tornado genesis as revealed by numerical investigations

Thursday, 6 November 2014: 2:45 PM
Madison Ballroom (Madison Concourse Hotel)
Gregory J. Tripoli, University of Wisconsin, Madison, WI; and S. Trevorow, L. Odell, and M. L. Buker

The analysis of several idealized and real data numerical investigations were compared to observations and have suggested several key dynamical structures found in supercells that result in top down tornado genesis. Results suggest that the supercell mesocyclone is built from individual vortical plumes that systematically interact with the environment and collectively act to produce the commonly accepted supercell structure. The organization of these structures is driven by interaction of these plumes with several key vertical layers including upper level shear or stable layers, the melting zone, and the overshooting top. Of critical importance is an entrainment “slot” that forms in the rear of the storm running the entire depth of the cell. Dynamic entrainment of environmental air into the slot energizes the formation of a cold toroidal circulation “daisy-chained” to the updraft toroid that stretches the mesocyclone downward to the surface. Deformation processes along the surface boundary act to converge the vorticity onto the gust frontal boundaries . This produces a surface vortex sheet that is rolled up onto a primary spindle supported by the dynamic pressure gradient aloft. At the base of the spindle a surface low pressure anomaly appears, rendered as a circular blue dot. It signifies the completed formation of a balanced vortex coupled to the upper level daisy chain that becomes the focal point of tornado genesis.
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