What radar-detected rotation algorithm is abbreviated TVS?

TVS is the abbreviation for a tornadic vortex signature, a rotation algorithm detected by pulse-Doppler weather radar.

A TVS identifies a very strong, organized rotation within a thunderstorm, usually associated with a powerful mesocyclone and possible tornado development. On radar velocity imagery, the feature often appears as adjacent inbound and outbound wind velocities—a tight velocity couplet showing air moving rapidly toward and away from the radar.

The signature was first recognized in research on the 1973 Union City tornado by scientists including Donald Burgess, Leslie Lemon, and Rodger Brown at the National Severe Storms Laboratory. Modern National Weather Service systems use updated tornado-detection methods with data from WSR-88D radars.

A common misconception is that a TVS proves a tornado is already on the ground. It does not. The algorithm usually detects rotation aloft, and forecasters combine it with storm structure, reports from spotters, reflectivity features, and sometimes a tornadic debris signature. Some tornadoes do not produce a clear TVS, especially weak or shallow tornadoes, while strong non-tornadic rotation can occasionally trigger one.