Tuesday, 29 August 2023: 1:45 PM
Great Lakes BC (Hyatt Regency Minneapolis)
On the afternoon of 20 May 2019, airborne and ground-based radars observed a tornadic supercell as it tracked northeastward out of Texas into southwestern Oklahoma as a part of the Targeted Observations by Radars and Unmanned Aircraft Systems of Supercells (TORUS) experiment. The NOAA P-3 with its forward and aft-angled X-band Tail Doppler Radars (TDRs) arrived on station at 2024 UTC and began executing dual-Doppler flight legs ahead of the storm as it passed north of Paducah, TX. The supercell initially produced several brief, weak tornadoes after 2024, followed by an EF-2 tornado from 2212-2229 UTC that did damage in N/NW Mangum, OK. The X-band NSSL NOXP mobile radar provided valuable collocated observations of the storm enabling more accurate, close-range triple-Doppler supercell analyses spanning five volumes from 2142 UTC through tornadogenesis time. By 2330 UTC, the P-3 had completed 20 dual-Doppler legs – one every ~5-10 min – yielding 3 hours of dual- and triple-Doppler radar observations.
This study documents the structural and kinematic evolution of the 20 May supercell through multiple rounds of tornadogenesis, employing the time-spaced multi-Doppler analyses aided by observations from mobile and fixed mesonets, soundings, and profilers. Key highlights include the 3-D radar analyses spanning almost 2 hours prior to the EF-2 tornado and documentation of the pre-tornadogenesis, tornado-cyclone maintenance, and tornado-cyclone decay phases. Particular attention is paid to the identification and characterization of the evolving kinematic storm-scale features, including: (a) the rear-flank gust front, rear-flank internal surge, left-forward flank, and forward flank convergence boundaries; (b) streamwise vorticity currents and left-flank vertical vorticity sheets; and (c) general main updraft and downdraft characteristics (e.g., magnitude, width). Initial results indicate that the main updraft exceeded 80 m s−1 at multiple analysis times, in line with the theoretical max of ~ 87 m s−1 given the MLCAPE of 3787 J kg−1 observed in the 2143 UTC NSSL far-field sounding. Backward trajectories computed from the Diabatic Lagrangian Analysis method will assist in identifying inflow source regions, while asymptotic contraction analysis will help assess the potential locations of surface-based internal, frontogenetically forced baroclinic boundaries.
This study documents the structural and kinematic evolution of the 20 May supercell through multiple rounds of tornadogenesis, employing the time-spaced multi-Doppler analyses aided by observations from mobile and fixed mesonets, soundings, and profilers. Key highlights include the 3-D radar analyses spanning almost 2 hours prior to the EF-2 tornado and documentation of the pre-tornadogenesis, tornado-cyclone maintenance, and tornado-cyclone decay phases. Particular attention is paid to the identification and characterization of the evolving kinematic storm-scale features, including: (a) the rear-flank gust front, rear-flank internal surge, left-forward flank, and forward flank convergence boundaries; (b) streamwise vorticity currents and left-flank vertical vorticity sheets; and (c) general main updraft and downdraft characteristics (e.g., magnitude, width). Initial results indicate that the main updraft exceeded 80 m s−1 at multiple analysis times, in line with the theoretical max of ~ 87 m s−1 given the MLCAPE of 3787 J kg−1 observed in the 2143 UTC NSSL far-field sounding. Backward trajectories computed from the Diabatic Lagrangian Analysis method will assist in identifying inflow source regions, while asymptotic contraction analysis will help assess the potential locations of surface-based internal, frontogenetically forced baroclinic boundaries.
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