The Kellerville Tornado during VORTEX: Damage survey and Doppler Radar analyses

Abstract

A detailed aerial and ground survey of a long-track (∼50 km) F5 tornado is presented. The survey revealed that the tornado exhibited unusual nonlinear movements at two different locations. One portion of the track was associated with a pronounced sinusoidal pattern while another location was characterized by a cusplike pattern. For the first time, high-resolution dual-Doppler wind measurements can be used to evaluate mechanisms for such deviations from a linear tornado path. The analyses of data collected with Electra Doppler Radar (ELDORA) suggest that these departures are trochoidal marks produced as the tornado was revolving within the larger-scale mesocyclone. Retrieved perturbation pressures indicate that the mesocyclone departed significantly from a cyclostrophically balanced state during these deviations. The maximum vorticity associated with the mesocyclone at low levels was shown to be an unreliable indicator of the tornado's intensity. Vertical cross sections of wind, vertical vorticity, radar reflectivity, and perturbation pressure were photogrammetrically superimposed onto two pictures of the tornado. This merger of data provides a unique view of the structural relationship between the hook echo and the mesocyclone. One of the important conclusions was the lack of a definitive relationship between the widths and strengths of the mesocyclone and the tornado.