School of Meteorology (Defense)
INTENSIFICATION OF LOW-LEVEL MESOCYCLONES AND ASSOCIATED STORMSCALE EVOLUTION IN SUPERCELL THUNDERSTORMS
Graduate Research Assistant
University of Oklahoma
School of Meteorology
24 June 2013, 3:00 PM
National Weather Center, Room 5820
120 David L. Boren Blvd.
University of Oklahoma
During the second field phase of the Verifications of the Origins of Rotation in Tornadoes Experiment, Part 2 (VORTEX2), a slow moving supercell thunderstorm was observed by the mobile armada on 26 May 2010 just northeast of Denver, Colorado. In this study, observations from six mobile radars; SR1, SR2, DOW6, DOW7, TTUKa1 and TTUKa2 along with surface thermodynamic measurements form the fleet of mobile mesonets have been used to analyze the three dimensional wind field and thermodynamic structure of the 26 May storm for the period 2230 UTC to 2244 UTC.
Between these times, the cyclic nature of the storm was revealed with an occluded circulation exiting the rear of the storm simultaneously with the development of a new low-level mesocyclone along the leading edge of the hook echo. Pulses in the rear flank downdraft (RFD) and the occlusion downdraft were associated with an increase in the low-level vertical vorticity maxima within the main updraft where maximum stretching occurred. Yet, the high base storm was unable to generate a long-lived, strong, small-scale circulation associated with a tornado vortex. Instead, the storm produced two short-lived, small-scale vortices. Thermodynamic measurements show the structure of the inflow and outflow regions of the storm as well as regions in the forward flank. The evolution of the RFD and occlusion downdraft was then compared to the evolution of two different storms sampled with the two mobile C-band radars (SR1 and SR2) on 29 May 2004 near Geary, OK and on 19 June 2010 near Concordia, KS. Similarities and differences in the downdraft evolution and subsequent evolution of the low level mesocyclone of these three storms were investigated.
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