What is a Tornado Vortex Signature and how does it appear on a Doppler radar screen?
Tornadic Vortex Signature (or TVS for short) is the signature of a tornado, or tornado-like vortex as seen in radial velocity fields of the Doppler radar. Radial velocity is defined as the wind speed either directly away from the radar beam or directly toward the radar beam (Doppler radar cannot measure winds that blow “perpendicular”, or directly across the radar beam). The TVS usually shows up a very small area (about 1/2 to 1 mile in diameter) of strong radial velocities, where half of the velocities are toward the radar, and the other half are away from the radar. When different colors are used to depict velocities blowing away from the radar versus toward the radar, the TVS will show up as adjacent areas of contrasting colors on the radar screen. The National Oceanic and Atmospheric Administration’s National Severe Storms Laboratory has developed “algorithms” (or computer programs) that can automatically detect TVSs using Doppler radial velocity data, leading to an increase in the
