Diagnosing new details about tornado dynamics

Using a single-Doppler dataset, the ground-based velocity-track-display (GBVTD)technique was employed to retrieve, for the first time, the detailed 3D dynamical structure of a tornado. With GBVTD, the axisymmetric ring-like vorticity field of the tornado, with peak values of more than 0.3 s^-1, was explicitly resolved and found to exhibit the necessary condition for barotropic instability. A strong central downdraft and an annular downdraft were revealed. Near-surface regions exhibiting convergence and divergence were mapped. The distribution of pressure inside the tornado was deduced, with deficits as high as 84 hPa. For the first time, the swirl ratio of an observed tornado was calculated, consistent with the observed two-cell, multiple-vortex structure. Periodic oscillations in core-flow radius, intensity, and intensity of low-level inflow were also correlated.