4A.3 Dual-Doppler and polarimetric observations of a tornadic supercell in central Oklahoma on 19 May 2013

Tuesday, 15 September 2015: 11:00 AM
University AB (Embassy Suites Hotel and Conference Center )
Zachary B. Wienhoff, University of Oklahoma, Norman, OK; and H. B. Bluestein, J. Houser, J. C. Snyder, A. Shapiro, and C. K. Potvin

On 19 May 2013, two supercells moved through central Oklahoma and produced seven tornadoes, including one of EF-3 and one of EF-4 intensity. High temporal and spatial resolution observations were collected in both strong tornadoes by a mobile, rapid-scan, X-band, polarimetric radar (RaXPol). In conjunction with the nearby WSR-88D Twin Lakes radar, dual-Doppler analyses were synthesized to produce the three-dimensional wind field and vertical vorticity throughout the tornadoes' lifecycles. In order to account for significant differences in the temporal resolutions of the two radars, a reflectivity-tracking scheme was employed to interpolate linearly (in a Lagrangian sense) between two radar volumes through a variational algorithm. Our analyses are unique because they are one of the first, to the authors' knowledge, to make use of data from both an operational, S-band radar and a mobile, rapid-scan, X-band radar. Additionally, it is one of the first close-range dual-Doppler wind syntheses of a tornadic supercell to contain polarimetric data. We will present a case study on the second tornado, the Norman-Shawnee tornado, and will assess the characteristics of the wind field associated with the intensification, maturity, and demise of the tornado. The 3-D wind fields of the tornado and mesocyclone will be examined to see how they evolved in time, and especially how vertical vorticity and vertical velocity changed as the tornado intensified. Differential reflectivity from the WSR-88D will be compared to the vertical velocity field estimated from dual-Doppler analyses to examine how the characteristics of a ZDR column varied with respect to changes in the updraft intensity. In addition, ~3 minutes of single-Doppler data near peak tornadic intensity were collected in which small-scale features are resolvable due to the close proximity of the mobile radar to the tornado (<4 km). Evolution of the maximum wind speeds with height from this data will be presented and small-scale features will be discussed.
- Indicates paper has been withdrawn from meeting
- Indicates an Award Winner