S73 Observational and Numerical Identification of Downdraft Generated Surface Vertical Vorticity

Sunday, 7 January 2018
Exhibit Hall 5 (ACC) (Austin, Texas)
Jacob Vancil, Texas Tech University, LUBBOCK, TX; and J. Dahl

Prior research has shown the importance of near ground vertical vorticity as a requirement for tornado genesis and maintenance. However, aspects remain unknown regarding the generation, strength, location, and movement of this near ground vertical vorticity. This research aims to examine and support previous work displaying the generation of near ground vertical vorticity in regions of negatively buoyant sheared downdrafts. With the use of two outflow-dominant storm observational data sets from June 2016 the mechanism for near ground vertical vorticity production will be investigated. The two radar data sets were collected using the two TTU Ka-band radars, which employs a 0.33-degree beamwidth. These two radars provide the data necessary for the dual doppler analysis of the three-dimensional wind fields for each of the above storm cases. In addition to the observational component of this work, further research investigates near ground vertical vorticity using the Bryan Cloud Model 1 (CM1). CM1 has been utilized to analyze the sensitivity of the microphysics scheme (single-moment vs. double-moment) on the development of near ground vertical vorticity. These simulations employ environmental soundings from the above two cases, as well as environmental soundings from select Vortex Southeast project cases (VSE), and the idealized Weisman-Klemp sounding. The poster will present results from the dual-Doppler analysis and model simulations, assessing the ability of the simulations to reproduce observed surface vorticity patterns.
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