Casey Griffin - March 29

High-Temporal Resolution Observations of Tornadoes Using the Atmospheric Imaging Radar 

Casey Griffin

Friday, March 29^th

3:00pm/NWC 5600

Advisors: Dr. Robert Palmer and Dr. David Bodine

Phased array radars provide flexible scanning strategies and high-temporal resolution data, which is particularly useful for studying rapidly evolving features, like tornadoes, which have advective timescales of 10 s or less.  This study uses high-temporal resolution tornado data collected by the Atmospheric Imaging Radar (AIR) to investigate the vertical evolution of rotation during tornadogenesis and tornado decay, a topic of particular interest in recent rapid-scan radar studies.  The AIR is particularly well suited to observe the vertical evolution of rotation within tornadoes and mesocyclones because it collects simultaneous RHIs, which minimizes horizontal advection and tornado evolution during collection of volumetric data.

This study includes observations of tornadogenesis during the 23 May 2016 Woodward, OK, tornado where the AIR collected one hour of continuous, 7-s volumetric updates that span the intensification stages of the supercell and the entire lifecycle of a tornado at 18-20 km in range.  The second dataset is the 27 May 2015 Canadian, TX, tornado where the AIR documented multiple modes of tornado decay, including simultaneous and downward weakening of vortex intensity.  A persistent layer of vortex tilt was observed near the level of free convection, which separated the two tornado decay modes.  A 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 in the vertical throughout the observation period, unlike some other recently observed tornado cases.  Finally, a novel interrogation of the vertical structure of near-tornado weak-echo reflectivity bands in the 16 May 2017 Wheeler, TX, tornado is presented.