Difference between revisions of "Tornado"

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== tornado ==
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== Tornado ==
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<div class="definition"><div class="short_definition">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.</div><br/>
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<div class="paragraph">Characteristics of typical tornadoes include a diameter of 2 km or less, with maximum [[wind]] [[velocity]] differences across the circulation exceeding 40 m s<sup>&minus;1</sup> within 200 m of the surface. Tornadoes typically last on the order of 100&ndash;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 Scale|enhanced Fujita (EF) scale]] have wind gusts at 10 m above the surface equaling or exceeding 29 m s<sup>&minus;1</sup> (65 mph; the lower bound of EF-0).</div><br/>
  
#<div class="definition"><div class="short_definition">A violently rotating column of air, in contact with the surface, pendant from a [[cumuliform]] cloud, and often (but not always) visible as a [[funnel cloud]].</div><br/> <div class="paragraph">When tornadoes do occur without any visible funnel cloud, debris at the surface is usually the  indication of the existence of an intense [[circulation]] in contact with the ground. On a local [[scale]],  the tornado is the most intense of all atmospheric circulations. Its [[vortex]], typically a few hundred  meters in diameter, usually rotates cyclonically (on rare occasions anticyclonically rotating tornadoes have been observed) with [[wind speeds]] as low as 18 m s<sup>&minus;1</sup> (40 mph) to wind speeds as high as  135 m s<sup>&minus;1</sup> (300 mph). Wind speeds are sometimes estimated on the basis of wind damage using  the [[Fujita scale]]. Some tornadoes may also contain secondary vortices ([[suction vortices]]). Tornadoes  occur on all continents but are most common in the United States, where the average number of  reported tornadoes is roughly 1000 per year, with the majority of them on the central plains and  in the southeastern states (''see'' [[Tornado Alley]]). They can occur throughout the year at any time  of day. In the central plains of the United States they are most frequent in spring during the late  afternoon. ''See also'' [[supercell tornado]], [[nonsupercell tornado]], [[gustnado]], [[landspout]], [[waterspout]].</div><br/> </div>
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<div class="paragraph">Tornadoes that occur over water are classified as [[waterspout|waterspouts]]. [[landspout|Landspouts]] are a subset of tornadoes that occur independent of a parent [[mesocyclone]]. [[gustnado|Gustnadoes]] are not considered tornadoes since they are shallow and short-lived vortices that are usually weak. [[dust devil|Dust devils]] are not considered tornadoes since they are not associated with cumuliform clouds.</div><br/> </div>
#<div class="definition"><div class="short_definition">A violent [[thundersquall]] in West Africa and adjacent Atlantic waters.</div><br/> </div>
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<p>''Term edited 2 November 2020.''</p>
  
 
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Latest revision as of 06:54, 2 November 2020



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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