Unmanned Aircraft System and Doppler Radar Observations of Rear-Flank Internal Surges in the 10 June, 2010 Last Chance, CO Supercell Observed During VORTEX2

On 10 June 2010, the VORTEX2 armada observed a supercell thunderstorm near Last Chance, CO. During a non-tornadic phase of the storm (after ~0130 UTC), several rear-flank internal momentum surges (RFIS) within an expanding rear flank outflow were observed. Surface thermodynamic data collected by sticknets and mobile mesonets are compared to thermodynamic measurements collected above the surface by the Tempest unmanned aircraft system and mobile sounding units to estimate vertical origins of air parcels within the rear flank outflow. Single and dual-Doppler analyses are performed using data collected by NOAA X-Pol (NOXP) and SMART-R's 1 and 2 in order to study the vertical structure of the rear flank outflow and to diagnose the likelihood that air within an RFIS was dynamically forced to the surface. Preliminary analysis of thermodynamic data collected by the Tempest UAS, in conjunction with surface thermodynamic data, suggests that some of the air within the rear flank outflow may have originated in low levels ahead of the primary rear flank gust front. This implies that some air parcels within the large scale rear flank outflow may have circulated through the wake behind the density current head back to the surface. This mechanism could account for the observations of potentially warm inflow air within the rear flank outflow and could produce secondary rear flank boundaries generated via kinematic frontogenesis rearward of the wake.