High-resolution radar analysis during tornadogenesis from OU-PRIME on 10 May 2010

High-resolution polarimetric radar measurements in numerous supercells and tornadoes were obtained by the Polarimetric Radar for Innovations in Meteorology and Engineering (OU-PRIME) during the 10 May 2010 tornado outbreak. These observations include a supercell that produced an EF-4 tornado that developed near Moore, Oklahoma, only 10–15 km from OU-PRIME. The supercell's reflectivity appendage developed cyclonic curvature 15 min prior to the first tornado observations, coincident with an increase in low-level mesocyclone intensity and a protrusion of the rear-flank downdraft into the inflow region. Numerous cyclonic and anticyclonic flares were observed along the rear-flank downdraft (RFD) with cyclonic and anticyclonic rotation below 100 m, indicative of possible tornadoes or gustnadoes. As the RFD gust front extended further into the inflow region, vortices developed along the RFD gust front after a significant increase in near-surface convergence along the RFD gust front. In general, the vortex diameter and the spatial concentration both decreased as height increased.

To analyze the evolution of low-level rotation during tornadogenesis, single-radar approximations of vorticity and convergence in the RFD region are computed. Vorticity and convergence are computed using radial velocity differences between two gates over a fixed number of gates. The possible role of vorticity along the RFD gust front in tornadogenesis will be discussed, along with other vorticity sources identified in the analysis.