TTUKa Radar Observations of Horizontal Vorticity Maxima Associated with Rear Flank Downdrafts and Gust Fronts

This presentation will focus on two specific cases of RHI observations made by the Texas Tech Ka-band mobile Doppler radars during VORTEX2. The first of these cases, 12 May 2010, reveals the finescale vertical structure of the rear-flank gust front (RFGF) as it passed near Willow, OK. A double-fineline structure is noted at times, as well as discrete propagation at all altitudes. Perhaps most interesting are a series of tight rotor circulations that are observed to develop along the RFGF interface at 2-3 km AGL, amplifying to an inferred horizontal vorticity of O~(10^-1 s^-1) as they ascend. The development of these vortices appears to coincide with when the RFGF transitions from an eastward-inclined to a (more typical) westward-inclined orientation. These observations will be framed in the context of PPI data from the Doppler on Wheels platforms as well as other VORTEX2 radar assets.

The second case discussed will reveal RHI observations of a reflectivity cascade within the hook echo of a supercell thunderstorm near Tribune, KS on 25 May 2010. This cascade initiates near 5 km AGL, impacts the surface approximately three minutes later within the body of the hook echo, and precedes the genesis of a weak tornado by a few minutes. This feature will be related to the notion of a descending reflectivity core, with potential implications on the vorticity budget of the Tribune, KS low-level mesocyclone addressed.