Ka and X-band radar observations of multiple rear-flank downdraft surges and an intense near-surface vortex on 18 May 2010

Multiple mobile Doppler radars participating in the second Verification of the Origin of Rotation in Tornadoes Experiment (VORTEX2) sampled several rapidly evolving rear-flank downdraft (RFD) surges as well as a short-lived, intense near-surface vortex occurring within a supercell on 18 May 2010 near Dumas, Texas. Two Ka-band, 35 GHz radars operated by Texas Tech University (TTUKa) collected a dual-Doppler dataset with a 3.5 km baseline of the near-surface wind field under the mesocyclone. The 18 minute dual-Doppler dataset captures three internal RFD surges evolving on a small temporal and spatial scale as well as the genesis of a brief, intense near-surface vortex at the apex of an internal RFD surge. The TTUKa dataset is coupled with high temporal resolution data from the MWR-05XP phased array mobile Doppler radar operated by the University of Oklahoma and the Naval Postgraduate School which sampled a complete volume of the storm mesocyclone at the X-band every 10-12 seconds.

The TTUKa data are limited to elevation angles of 0.5 degrees and below; therefore, the MWR-05XP volumes have been analyzed separately to provide insight into the vertical extent and evolution of the RFD surges and vortex development. Diagnosis of the vertical origin of each RFD surge in MWR-05XP data will allow for speculation on the forcing mechanism of each surge and potential thermodynamic differences between RFD surges.