Tornado
A rapidly rotating column of
air extending vertically from the surface to the base of a
cumuliform cloud, often with near-surface circulating debris/
dust when over land or spray when over water. Although its presence is not required, a
funnel cloud is often visible and may partly or fully extend from the cloud base to the ground.
Characteristics of typical tornadoes include a diameter of 2 km or less, with maximum
wind velocity differences across the circulation exceeding 40 m s
−1 within 200 m of the surface. Tornadoes typically last on the order of 100–1000 s. Some may be comprised of multiple subvortices with spatial scales as small as tens of meters, rotating around a central axis. Tornadoes rated by the
enhanced Fujita (EF) scale have wind gusts at 10 m above the surface equaling or exceeding 29 m s
−1 (65 mph; the lower bound of EF-0).
Tornadoes that occur over water are classified as
waterspouts.
Landspouts are a subset of tornadoes that occur independent of a parent
mesocyclone.
Gustnadoes are not considered tornadoes since they are shallow and short-lived vortices that are usually weak.
Dust devils are not considered tornadoes since they are not associated with cumuliform clouds.
Term edited 2 November 2020.
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