Single- and dual-Doppler analyses of a tornadic supercell sampled by NWRT PAR and WSR-88D

On 13–14 May 2009 a line of supercell storms formed along a cold front as it progressed eastward into central Oklahoma. One of these supercells impacted the Oklahoma City metropolitan area, producing hailstones up to 2.5 cm in diameter, heavy rain, and an EF0-rated tornado. Two cycles of this tornadic supercell were sampled by the National Weather Radar Testbed Phased-Array Radar (NWRT PAR) in Norman, Oklahoma. During this period (0309-0350 UTC on 14 May), the mesocyclone was located within 30 km of the NWRT PAR and sampled using an elevation-prioritized scanning strategy that produced 43 s updates at the two lowest elevations. Concurrently, this supercell was sampled by the Weather Surveillance Radar–1988 Doppler (WSR-88D) located in southeast Oklahoma City (KTLX).

Single-Doppler objective analyses of the NWRT PAR data render the complex, cyclic low-level evolution of the supercell as revealed by the radar's rapid sampling, including the occlusion of the initial cyclonic mesocyclone, the development of an anticyclonic mesocyclone, and the evolution of several short-lived circulations, one of which produced the EF0-rated tornado. Additionally, a series of dual-Doppler analysis of the NWRT PAR and KTLX data are performed every ~4 min through the lowest ~5 km, providing a storm-scale context to help interpret the dynamics of the rapid changes in low-level circulations revealed by the frequent low-level NWRT PAR scans. Results are focused on the dynamical structure of the low-level mesocyclone and the short-lived embedded vortices in relation to the storm-scale updraft and the forward- and rear-flank downdrafts and outflow boundaries.