Kinematic Observations of Tornadic Debris Signatures in Two Supercells during the 10 May 2010 Oklahoma Tornado Outbreak

The ability of tornadoes to loft non-meteorological scatters that present irregular shapes and sizes, near random orientations, and a wide range of dielectric constants allow polarimetrically diverse radars to discriminate between meteorological scatterers and tornadic debris. The unique polarimetric signature associated with lofted non-meteorological scatterers is called the tornadic debris signature (TDS). Previous studies have identified that the TDS is characterized by a large range of radar reflectivity factors (Z_HH), low values of copolar cross-correlation coefficients (ρ_hv), and differential reflectivity (Z_DR) values near zero. Previous work has also documented that tornado damage measured using the enhanced Fujita scale (EF) rating correlates well the magnitude of reflectivity within the TDS as well as the height and volume of the TDS. While ties between TDS characteristics and tornado- and storm-scale kinematic processes have been speculated or investigated using single-Doppler analyses, little work has been done to document the three-dimensional wind fields associated with an evolving TDS.

This study uses data collected by KTLX and KOUN WSR-88D S-band radars as well as the University of Oklahoma's Advanced Radar Research Center's OU-PRIME C-band radar to construct dual-Doppler analyses of two tornadic supercells which produced tornadoes near Moore and Norman, OK on 10 May 2010. Dual-Doppler analyses will be used to examine two and three-dimensional flow near and within the TDS during various stages of the two tornadoes' lifecycles. TDS volume and height will be compared to kinematic properties such as vertical velocity, horizontal wind shear, and vertical vorticity in order to confirm whether any correlation exists between the depth and shape of the TDS and the strength of the tornado. Additional analysis will include forward trajectories of debris within the TDS using dual-Doppler derived wind fields. Finally, backward trajectories will be performed to determine the origin of parcels entering the TDS and whether a change of parcel source region can explain the contamination of the TDS often theorized to be associated with precipitation entrainment.