Usually Doppler radar is used.
Doppler radar is a very useful tool, as it can detect the kind of rotation that can produce a tornado.
Usually scientists do not use any tool to determine how strong a tornado is. Usually the strength of a tornado is determined based on the severity of damage it causes. Occasionally wind speed measurements are obtained using Doppler radar, but such measurements are rare.
You use it when you are comparing data.
A
The largest tornado on record ocurred near El Reno, Oklahoma on May 31, 2013. It was 2.6 miles wide.
A single smart person on a motorcycle with a cell phone link to another smart person at a computer connected to the internet could track a tornado. About 99% of the other stuff is just sensationalism and a means to produce some kind of "documentary" that can be sold to television. Those who are really serious about tracking down a tornado have a truck with a Doppler radar unit on it. Everyone else is just a "pretender" who in interested in film production rather than meteorology. In this light, one truck would be enough. A second truck could Cary "chasers" and the larger unit with the radar could stay out of harm's way. In that case, two trucks would do it. The use of a vehicle hauling a Doppler radar unit separates the "real players" from the "wannabes" out there - and there are a lot of the latter.
Jupiter has a big red spot. It is not just any old spot though, it is some kind of on-going tornado. If you head directly to it & reach Jupiter's atmosphere, you will be sucked into the dot (or tornado) and probably die...
the tornado kind
A tornado is a kind of vortex so yes, in some ways.
A tornado is itself a kind of vortex, and can have smaller vortices inside of it.
A tornado emergency is a special kind of tornado warning that is issued when a large tornado is threatening a populated area. A tornado emergency indicates a more dangerous situation than an ordinary tornado warning.
That rather depends in which context you mean ! When I first saw this question - the transponder I immediately thought of - is the kind that's built-in to an aircraft. An aircraft transponder is a small box of electronics, that transmits a constant stream of data - including the plane's identity, height, speed and radar heading. The control tower sees the data alongside a corresponding 'blip' on the radar screen.