Tornado: Difference between revisions

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== 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.<br/>


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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).<br/>
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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.<br/>  
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== tornado ==


<div class="definition"><div class="short_definition">A rotating column of air, in contact with the surface, pendant from a [[cumuliform]] cloud, and often visible as a [[funnel cloud]] and/or circulating debris/dust at the ground.
<p>''Term edited 2 November 2020.''</p>
On a local [[scale]], the tornado is the most intense of all atmospheric [[circulation]]s. Its vortex usually rotates [[Cyclonic rotation|cyclonically]] (on rare occasions [[anticyclonic rotation|anticyclonically]] rotating tornadoes have been observed) with [[wind speed]]s as low as 30 m s-1 (67 mph) to as high as 135 m s-1 (300 mph), and is generally < 2 km (1.25 mi) in diameter. Tornado [[intensity]] is often estimated on the basis of wind damage using the [[Enhanced Fujita Scale]]; however, this estimate can be refined using other measurements, especially in the absence of damage indicators. Some tornadoes may also contain secondary [[vortex|vortices]] (also referred to as [[suction vortices]], subvortices, multiple, and satellite vortices).Tornadoes have been observed on all continents except Antarctica 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|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 [[fujita scale|Fujita Scale]].)</div><br/> </div>
 
''term edited 8Oct2013''
 
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Latest revision as of 23:46, 28 March 2024

Tornado[edit | edit source]

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.

Lines or surfaces associated with a partial differential equation, or with a set of such equations, which are at all points tangent to characteristic directions, determined by certain specified linear combinations of the equations.

  1. 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.
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