Fine-Scale Observations of Subvortices Within the Multiple-Vortex ‘El Reno Tornado' of 31 May 2013 Using a Rapid-Scan, Mobile, Doppler Radar

On 31 May 2013, the mobile, Rapid-scan, X-band, Polarimetric (RaXPol) Doppler radar collected a high spatiotemporal resolution dataset documenting the genesis, intensification, and dissipation of a tornado that caused EF-3 damage near El Reno, OK, although Doppler velocities measured by RaXPol exceeded 135m/s (EF-5 strength wind speeds) near the surface. The RaXPol mobile radar was deployed three times during the tornadic phase of this storm, between 4.5-11 km from the center of the tornado, and collected 360 degree PPI scans every 2 seconds with range gate spacing between 15 to 45 meters. Within the Doppler velocity data, multiple subvortices were resolved during the large, multiple-vortex phase of the El Reno tornado’s life cycle, over a time period of 132 seconds. Details about the origins, paths, and dissipations of at least two-dozen resolvable subvortices, some of which had translational speeds in excess of 75m/s, were documented. The subvortices mostly developed inside the radius of maximum winds and those that persisted for longer periods of time (>15 seconds) tended to traverse towards the center of the tornadic vortex over their life cycles. Finally, details regarding the evolution and kinematics of the subvortices were compared to composite background fields of radial velocity and spectrum width to draw conclusions regarding the areas of common subvortex genesis and dissipation. Azimuthal velocities of the subvortices will also be compared to the background radial velocity field to determine if they were retrograding with respect to the mean flow, as tornado vortex theory would suggest.