Tornado vortex signature

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A typical tornado vortex signature.

A tornado vortex signature, or tornadic vortex signature, (TVS), is a Doppler weather radar detected rotation algorithm that indicates a strong possibility of a tornado.

In most cases, the TVS is a tornadocyclone aloft, not a tornadic circulation. It is often visible on the Doppler radar storm relative velocity product as side by side inbound and outbound velocities. When the algorithm is tripped, a TVS icon and pertinent information appear. Radar analysis of the velocity couplet as well as the automated TVS are very significant to issuing tornado warnings and can suggest the strength and location of possible tornadoes. Although many tornadoes, especially the stronger ones, coincide with a TVS, tornadoes can and sometimes do occur without a TVS.

A TVS can be measured by gate to gate wind shear, which is the change of wind speed and direction across the the two gates of inbound and outbound velocities. Gates are the individual pixels on the radar display. For example, if the inbound velocity is -48 knots (-88.9 km/h) knots and the outbound is 39 knots (72 km/h), then there is 87 knots (161 km/h) of gate to gate shear. The impressiveness of a TVS not only has to do with the strength of the gate to gate shear, but it also incorporates the size and depth of the TVS, and the strength of any surrounding mesocyclone, among other things.