Description

The description 'Tornado' is most often applied to a violently spinning vortex of air with a diameter varying from a few to several hundred metres in which the central air pressure is extremely low and the horizontal pressure gradient near its centre intense. Deep atmospheric instability appears to be a prerequisite for its formation and so they are often associated with thunderstorms, heavy rain and hail such as occurs when Cumulonimbus (Cb) Cloud is present.