Radar, Unmanned Aircraft System, and Surface Observations of Rear Flank Internal Momentum Surge Formation

Based on recent in situ observations of tornadic supercells collected during VORTEX2, ANSWERS, and TWISTEX, surges of momentum in the rear flank gust front, or rear flank internal momentum surges (RFIS), are believed to be important for the genesis and growth of supercell tornadoes. Several supercells sampled by VORTEX2, including the 10 June 2010 Last Chance, CO supercell, will be investigated in order to determine forcing mechanisms for RFIS formation. In the 10 June Last Chance supercell, the observed RFIS was not associated with any tornadoes, as the surge in question occurred during a non-tornadic phase of the storm. However, a Tempest unmanned aircraft system collected above-ground thermodynamic observations of the rear flank gust front and a RFIS during the 0132 – 0205 UTC (11 June) period. These data will be analyzed along with single and dual-Doppler radar observations and surface thermodynamic observations in order to test multiple hypotheses relating precipitation pulses, the vorticity field, and density current wake dynamics to RFIS occurrence.