abbreviation TVS stands for Tornado Vortex Signature. One of three
terms will be used to describe the tornadic potential of a certain cell
in this column.
that a radar cannot scan the ground to look for a tornadic rotation,
which can lead to detection errors. The radar only obtains data from
the storm tower, and relies heavily on this to detect a tornado vortex
– The potential for a tornado is not existent according to
the radar when NONE is shown. That does not necessarily mean that a
tornado is not present, given tornadoes can sometimes form starting at
the ground, and make their way up. Always heed National Weather Service
– "Elevated Tornado Vortex Signature" – Circulation
does not extend all the way to the lowest tilt on radar with an ETVS,
but is strong among the other tilts. An ETVS should be monitored
closely for development into a TVS.
– If a TVS is identified by radar, a tornado is a good
possibility, because circulation has been detected through the lowest
possible tilt. However, since the radar beam does not pan all the way
down to the surface, there is no way to guarantee this. Listen to local
media to find out more information or see if storm spotters have
confirmed the feature.
Since the algorithm which detects the tornadic, or tornado, vortex
signature is sensitive, false signatures can at times be detected along
frontal boundaries and squall lines, or where a definite wind shift is
present, especially when the front edge of a squall line is parallel to
the radar beam. A TVS or ETVS does not guarantee a tornado.
When a TVS or ETVS is detected, the radar has found an area of intense
and concentrated rotation, more so than a mesocyclone. Watch this for
persistence. Other algorithm criteria, such as the strength and
vertical depth, must also be met for a radar to indicate a tornado
A TVS or ETVS itself is not a visually observable feature. The possible
tornado that could accompany such a signature obviously is visible
A radar cannot detect a tornado vortex signature well, or possibly at
all, if a thunderstorm is close to the radar site. Beams are unable to
extend into the updraft at such a degree from the radar's transmitter.
A lesser, or possibly absent, tornado vortex signature is displayed as
Do not question warnings issued by the expert National Weather Service
meteorologists. If you feel your life is threatened by a thunderstorm,
do not postpone seeking shelter, even if a warning is not in effect for