Wednesday, 9 November 2016: 5:00 PM
Pavilion Ballroom East (Hilton Portland )
The ability of tornadoes to loft non-meteorological scatterers that present irregular shapes and sizes, near random orientations, and a wide range of dielectric constants allow polarimetric radars to discriminate between meteorological scatterers and tornadic debris. The unique polarimetric signature associated with lofted non-meteorological scatterers is called the tornadic debris signature (TDS). Previous studies have documented that tornado damage measured using the enhanced Fujita scale (EF) rating correlates well the magnitude of reflectivity within the TDS as well as the height and volume of the TDS. Other studies have documented how factors like geography, land usage, and tornado lifecycle modulate the TDS. While ties between TDS characteristics and tornado- and storm-scale kinematic processes have been speculated or investigated using photogrammetry and single-Doppler analyses, little work has been done to document the three‑dimensional wind fields associated with the TDS.
This study uses data collected by KTLX and KOUN WSR-88D S-band radars as well as the University of Oklahoma’s Advanced Radar Research Center’s OU-PRIME C-band radar to construct single- and dual-Doppler analyses of a tornadic supercell that produced an EF-4 tornado near Moore, OK on 10 May 2010. The focus of this study is on the spatial distribution of polarimetric radar variables and how the variables relate to kinematic fields such as vertical vorticity. Special consideration will be given to a time when multiple vortices were observed within the tornado and how the polarimetric variables relate to these subvortices. An observation of negative differential reflectivity (ZDR) at the periphery of tornado subvortices, called the ‘ZDR wake’, is presented and discussed. Dual-Doppler wind retrievals are also compared to single-Doppler axisymmetric wind fields to illustrate the merits of each method.
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