High-resolution polarimetric observations of an EF4 tornado on 10 May 2010 from OU-PRIME

On 10 May 2010, OU-PRIME obtained high-resolution observations of an EF4 tornado that formed in Norman, Oklahoma and passed through Moore and southern Oklahoma City. Previous studies have documented a distinct polarimetric signature called the tornadic debris signature (TDS), characterized by low correlation coefficient values and near-zero differential reflectivity. This study investigates the evolution of the TDS and its relationship to the dynamics of the tornado and observed damage throughout the lifetime of the tornado. Radial velocity data from the National Weather Radar Testbed Phased Array Radar provide very high temporal resolution to examine the wind field of the tornado. In general, the lowest values of correlation coefficient are observed near the radius of maximum wind. During the mature phase of the tornado, OU-PRIME measured extremely low correlation coefficient values as low as 0.03, much lower than values previously documented at S-band. During one volume scan, a ring of small drops is observed around the tornado at about 1.5 km AGL, surrounded by debris both inside and outside the ring. A theory for how the ring could form around the tornado is proposed.