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Doppler Radar Observations of Vortices in a Left-Moving Supercell Thunderstorm on 26 May 2009

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Wednesday, 5 November 2014
Capitol Ballroom AB (Madison Concourse Hotel)
Mark D. Savin, University of Illinois, Urbana, IL; and J. W. Frame

Two Doppler on Wheels (DOW) radars observed a left-moving nontornadic supercell on 26 May 2009 near Dallas, TX, during the first field phase of the Verification of the Origins of Rotation in Tornadoes Experiment 2 (VORTEX2). Single-Doppler observations began while the storm was a left-moving supercell and continued for approximately half an hour, after which time a second radar also began scanning the storm. During the entire period of single-Doppler observations, as well as the first fifteen minutes of dual-Doppler observations, eight vortices were observed aloft in the southwestern portion of the storm. The vortices varied widely in strength, depth, temporal continuity, and width (defined as distance between maximum inbound and outbound velocities) and rotated both cyclonically and anticyclonically. The strongest and largest vortex, the likely mesoanticyclone, had a maximum velocity differential of 53 m s-1, maximum width of 2.89 km, and a maximum depth of at least 3.37 km. A statistical analysis reveals a slight positive correlation between the strength and width of the vortices, although this relationship is likely dominated by the presence of the mesoanticyclone. Little correlation was found between the strength and depth of the vortices. Other statistical analyses will also be presented. The vortices grew less numerous with time, and eventually dissipated as a wind shift propagated through the core of the storm. As the storm evolved, it later began to develop right-moving characteristics as the low-level clockwise hodograph curvature increased owing to the onset of the nocturnal low-level jet.