Is a rotating storm/hook echo NEEDED for a tornado to form?

Question

during a thunderstorm, does it have to be rotating or have a hook echo for a tornado to form? so if let say there is a severe thunderstorm happeing and there is no tornado warnings/watches, it means one cant form and wont then?

Answer 1

Yes. Without rotation, a tornado will not form. If there are no tornado watches or warnings, then that means the conditions are not favorable enough for tornado development. Tornadoes require a lot of energy to form and continue to rotate.

Answer 2

There has to be rotation in the sky for a tornado to form. Tornadoes form in funnel clouds before they touch down to earth.

Answer 3

Pegminer has a great answer, given that the question was Doppler-related. Try telling a thunderstorm that it cannot spawn a tornado just because the Doppler operator never detected a hook echo.

We have, in the past, practiced issuing tornado warnings off of a mesocyclone detection alone! I never cared for this because of too many unverified warnings, but oftentimes a hook echo signature, and especially a TVS (tornado vortex signature) is picked up on after the cyclone has already touched down. Too late!

I am kind of rambling, but I wanted to make that point because it is good to have an education of the reasoning behind many watches/warnings.

Forgive me if my Doppler lingo is outdated. I have not operated one in a few years.

Answer 4

If you are experiencing  severe thunderstorms, there is the potential for a tornado.  Many tornadoes form without tornado warnings and Doppler radar cannot always resolve a hook echo and rotation.

Obviously, tornadoes rotate so there must be rotation in the storm, but just because it's not seen on radar doesn't mean it's not there.  Also, the algorithm may have not have detected it or it could have formed in the interval between sweeps of the radar.

The last data that I saw was that more than 30% of tornadoes went unwarned.

Answer 5

Well without rotation/convection in a storm, a tornado can not form. A tornado starts inside a storm cloud when air begins to rotate inside of a cloud in a high enough rate, it can sink down, and form a torndao.

Well a tornado warning is issued once a hook echo sees an area in a cloud with rotation, and a tornado watch is issued when a tornado has been spotted or there is evidence to support that one has formed allready. Sometimes, by the time a warning is issued, a tornado may have formed already, and this gives people less time to prepare for a possible tornado in their area.

Overall, any storm that is strong enough with the right conditions can produce a tornado. So if you are in an area with storms that people are saying can produce tornados, be ready at a moments notice.

Answer 6

Rotation is one of the factors involved in tornadogenesis.  A hook echo is often indicative of a tornado, but not every tornado shows up as a hook echo.  The radar echo is actually the rain and hail surrounding the tornado itself, which is in the clear area inside the hook, but some storms don't generate enough precipitation for the hook echo to show up on radar.  If there is a severe thunderstorm warning, then a tornado watch is also automatically generated.  Occasionally a tornado will form out of what appears on radar to be non-severe.

Answer 7

people seem to think that rotation is only needed for a tornado to form, which it is one of the key components but updraft is also needed, which is the blowing up of hot air. thats also how hail forms. anyway, many clouds rotate but this does not mean that there is a tornado. without updraft AND rotation, the funnel coud will not touch the ground