High-Temporal Resolution Observations of the 27 May 2015 Canadian, Texas, Tornado Using the Atmospheric Imaging Radar

• Published in: Monthly weather review 2019-03, Vol.147 (3), p.873-891
• Main Authors: Griffin, Casey B., Bodine, David J., Kurdzo, James M., Mahre, Andrew, Palmer, Robert D.
• Format: Article
• Language: English
• Subjects: Aerodynamics; Air; Amplification; Azimuth; Beamforming; Convection; Cross correlation; Data collection; Decay; Deployment; Diameters; Digital imaging; Doppler sonar; Elevation; Free convection; Imaging radar; Imaging techniques; Meteorological data; Radar; Radar imaging; Radar observation; Resolution; Small-scale vortices; Steering; Studies; Superhigh frequencies; Temporal resolution; Tornadoes; Velocity; Vortices; Winds
• ISSN: 0027-0644; 1520-0493
• DOI: 10.1175/MWR-D-18-0297.1

On 27 May 2015, the Atmospheric Imaging Radar (AIR) collected high-temporal resolution radar observations of an EF-2 tornado near Canadian, Texas. The AIR is a mobile, X-band, imaging radar that uses digital beamforming to collect simultaneous RHI scans while steering mechanically in azimuth to obtain rapid-update weather data. During this deployment, 20°-by-80° (elevation × azimuth) sector volumes were collected every 5.5 s at ranges as close as 6 km. The AIR captured the late-mature and decaying stages of the tornado. Early in the deployment, the tornado had a radius of maximum winds (RMW) of 500 m and exhibited maximum Doppler velocities near 65 m s−1. This study documents the rapid changes associated with the dissipation stages of the tornado. A 10-s resolution time–height investigation of vortex tilt and differential velocity is presented and illustrates an instance of upward vortex intensification as well as downward tornado decay. Changes in tornado intensity over periods of less than 30 s coincided with rapid changes in tornado diameter. At least two small-scale vortices were observed being shed from the tornado during a brief weakening period. A persistent layer of vortex tilt was observed near the level of free convection, which separated two layers with contrasting modes of tornado decay. Finally, the vertical cross correlation of vortex intensity reveals that apart from the brief instances of upward vortex intensification and downward decay, tornado intensity was highly correlated throughout the observation period.