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An Evaluation of Normalized Rotation Vorticity Couplets to Assess Tornadic Mesocyclone Potential

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Wednesday, 5 November 2014
Capitol Ballroom AB (Madison Concourse Hotel)
T. J. Turnage, NOAA/NWS, Grand Rapids, MI

Azimuthal shear, used for NSSL Rotation Tracks and GR2Analyst Normalized Rotation (NROT), is a well-established tool for inferring vorticity, and therefore coherent circulations, from radar base velocity data. If a mesocyclone is well sampled and exhibits a Rankine vortex structure, the positive NROT maximum associated with the mesocyclone will be flanked by negative NROT regions where tangential velocity begins to decrease at increasing range from the circulation center. Anticyclonic flow associated with the presence of a rear-flank downdraft increases the magnitude of negative NROT to the southwest of the mesocyclone, resulting in a vorticity couplet that is often very apparent in the NROT data. This study will use GR2Analyst to evaluate trends of NROT vorticity couplets for tornadic versus non-tornadic mesocyclones to determine the utility of this feature for diagnosing tornadic mesocyclones.