High-Temporal-Resolution Observations of Weak-Echo Reflectivity Bands and Momentum Surges in the 16 May 2017 Wheeler, Texas, Tornado

The flexible scanning strategies and high-temporal resolution data of phased array radars facilitate the study of atmospheric processes that evolve on short timescales, including many high-impact weather phenomena. Phased array radars are particularly useful for studying tornadoes, which can change rapidly in less than 10 s. This study uses high-temporal resolution tornado data collected by the Atmospheric Imaging Radar (AIR), a mobile, X-band, imaging radar that uses digital beamforming to collect simultaneous RHI scans and steers mechanically in azimuth. The simultaneous RHIs are particularly useful for the study of tornadoes because horizontal advection and rapid tornado evolution do not need to be corrected for when interrogating vertical structure.

On 16 May 2017 the AIR collected 7-second-resolution 110° azimuth x 20° elevation sector volumes of an EF-2 tornado that occurred near Wheeler, Texas. The Wheeler, Texas, tornado was sampled as close as 10 km in range and was approximately 1 km in diameter with maximum measured delta-v of ~90 m s^-1 during the 10-minute deployment. The purpose of this study is to document the temporal evolution of the weak-echo reflectivity bands that were observed to wrap around the tornado during the deployment. Among the analyses will be simultaneously collected RHIs that show horizontal vorticity adjacent to the weak-echo reflectivity bands. Additionally, this study documents how an observed momentum surge within the rear-flank downdraft modifies tornado intensity and causes asymmetry in the velocity couplet. Finally, observations of the development of an anticyclonic vortex aloft that exhibited delta-V in excess of 30 m s^-1 are presented.