An ascending current of air occurring in a relatively restricted region of a cumulonimbus cloud, multicell or supercell storm, tropical cyclone, or similar system. Updraughts originate when more general ascending currents in thermals become concentrated and organized into a single flow, often in response to the development of a strong, cold downdraught. When the latter hits the ground and fans out ahead of a storm, it may lift a significant amount of air into the developing system. Updraughts may also originate as a compensating flow to a violent downdraught, and this mechanism is thought to be important in the formation of landspouts and waterspouts. In supercell storms, the updraught develops into a large rotating mesocyclone, which may then give rise to tornadoes.
Subjects: Meteorology and Climatology.