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Tornado
From SKYbrary Wiki
| Article Information | ||
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| Category: | Weather | 
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| Content source: | SKYbrary | 
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| Content control: | EUROCONTROL | 
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| WX | |
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| Tag(s) | Weather Phenomena |
Contents |
Definition
A violently spinning vortex of air extending down from the base of a Cumulonimbus Cloud and in contact with the surface, often visible as a funnel cloud.
Description
A Tornado has the appearance of a narrow funnel with a cloud of debris near the ground. Depending on the moisture content of the air, the funnel may be visible due to condensation and often takes on the colour of the earth and debris that is being sucked up by the funnel. The central core of the funnel is extremely low pressure and winds surrounding the tornado typically reach around 180 km per hour.
There are numerous types of tornado but the most destructive occur when a mesocyclonic rotation exists in the middle layers of the thunderstorm. Strong downdrafts at the trailing edge of the storm drag that rotating mesocyclone towards the ground and the funnel cloud forms beneath the cloud and extends towards the ground as the vortex spins faster. Eventually, the cold downdrafts cut off the supply of warm air which feeds the tornado and the updraft within the cloud above, and the tornado dissipates.
- Climatology.Tornadoes are most common in mid latitudes, in spring, and in the late afternoon, and are associated with severe Thunderstorms. Tornadoes can cause considerable damage and loss of life. The most severe Tornadoes occur in eastern India, Bangladesh, and in the mid western states of the USA and southern Canada, often referred to as "Tornado Alley".
- Indications. If the base of the cloud has well defined and extensive Mammatus cloud structures and the strength of the updrafts within the cloud are strong enough to push up through the Tropopause, indicated by a central bulge in the anvil shaped top to the cloud, then it is possible that the storm is severe enough to generate tornadoes.
Effects
A Tornado can cause considerable damage to airport and air traffic control infrastructure if it touches down on an aerodrome; any aircraft caught on the ground in the path of a tornado will quite possibly be damaged beyond repair. It is difficult to imagine any aircraft surviving the experience of encountering a tornado in the air. If aircraft cannot be evacuated, then damage to the aircraft, and other aircraft and infrastructure, may be lessened by securing the aircraft to the ground.
For further information on the hazards associated with thunderstorms, see the main article Cumulonimbus.
Accidents and Incidents
- On 6 October 1981, a Fokker F-28 operated by NLM Cityhopper broke up in flight after flying into severe turbulence and a tornado, crashing near Moerdijk in the Netherlands. 17 crew and passengers were killed. (Source: Aviation Safety Network)
Airports where tornados occur
- KAEX (Alexandria/Louisiana)
- KATL (Atlanta/Hartsfield-Jackson International)
- KBHM (Birmingham-Shuttlesworth)
- KBTR (Baton Rouge Metropolitan)
- KCHA (Chattanooga Lovell)
- KDAL (Dallas Love Field)
- KDFW (Dallas-Fort Worth)
- KESF (Alexandria/Esler)
- KHSV (Huntsville)
- KLIT (Little Rock National Airport/Adams Field)
- KMCI (Kansas City International)
- KMEM (Memphis)
- KMSY (New Orleans)
- KPDK (DeKalb-Peachtree)
- KPNS (Pensacola)
The following map shows the aerodromes where tornados occur across the world which are listed on SKYbrary: