|
Intensity |
Description |
Wind speed |
Windspeed |
Characteristics |
|
T0 |
Light Tornado |
17-24 |
61-86 |
Loose light litter raised from ground-level in spirals. Tents, marquees seriously disturbed; most exposed tiles, slates on roofs dislodged. Twigs snapped; trail visible through crops. |
|
T1 |
Mild Tornado |
25-32 |
90-115 |
Deckchairs, small plants, heavy litter made airborne; minor damage to sheds. More serious dislodging of tiles, slates, chimney pots. Wooden fences flattened. Slight damage to hedges and trees. |
|
T2 |
Moderate Tornado |
33-41 |
118-148 |
Heavy mobile cranes displaced, light caravans blown over, garden sheds destroyed, garage roofs torn away, much damage to tiled roofs and chimney stacks. General damage to trees, some big branches twisted or snapped off, small trees uprooted. |
|
T3 |
Strong Tornado |
42-51 |
151-184 |
Mobile homes overturned/badly damaged; light caravans destroyed; garages, outbuildings destroyed; house roof timbers considerably exposed. Some of the bigger trees snapped or uprooted. |
|
T4 |
Severe Tornado |
52-61 |
187-220 |
Mobile homes destroyed; some sheds airborne for considerable distances; entire roofs removed from some houses or prefabricated buildings; roof timbers of stronger brick or stone houses completely exposed; possible collapse of gable ends. Numerous trees uprooted or snapped. |
|
T5 |
Intense Tornado |
62-72 |
223-259 |
Motor cars levitated; more serious building damage than that for T4, yet house walls usually remaining; the weakest, old buildings may collapse completely. |
|
T6 |
Moderately-devastating Tornado |
73-83 |
263-299 |
Heavy motor vehicles levitated; strong houses lose entire roofs and perhaps also a wall; more of the less strong buildings collapse. |
|
T7 |
Strongly-devastating Tornado |
84-95 |
302-342 |
Frame houses completely demolished; some walls of stone or brick houses beaten down or collapse; steel-framed warehouse-type buildings may buckle slightly. Locomotives thrown over. Noticeable de-barking of any standing trees by flying debris. |
|
T8 |
Severely-devastating Tornado |
96-107 |
346-385 |
Frame houses and their contents dispersed over big distances; most other stone or brick houses irreparably damaged; steel-framed buildings buckled; motor cars hurled great distances. |
|
T9 |
Intensely-devastating Tornado |
108-120 |
389-432 |
Many steel-framed buildings badly damaged; locomotives or trains hurled some distances. Complete debarking of any standing tree trunks. |
|
T10 |
Super Tornado |
121-134 |
436-482 |
Entire frame houses and similar buildings lifted bodily from foundations and carried some distances. Steel-reinforced concrete buildings may be severely damaged. |
Tornado intensities can be grouped thus:
T0, T1, T2, T3 Weak Tornadoes
T4, T5, T6, T7 Strong Tornadoes
T8, T9, T10, T11 Violent Tornadoes
Scale devised in United Kingdom to categorise windspeeds in tornadoes. The scale is directly related to, and a natural extension of, the Beaufort Scale. The scale allows for windspeed rating based on direct viewing or engineering analysis of damage, Doppler radar, photogrammetric analysis, and/or direct measurement.
The rating assigned is always that where the tornado was most intense. Adjacent points can be grouped together – e.g., T7-8 is quite acceptable. As the scale is a true windspeed scale, strictly speaking it can also be used to measure any windspeed of any intensity, regardless of whether the wind is tornadic or not.
The TORRO Tornado Intensity Scale is open-ended and may be continued above T10 by use of the appropriate formulae:
v = 2.365 [T+4]1.5 metres per second
v = 8.511 [T+4]1.5 km/h
B = 2[T+4]
T = [B/2] – 4
where v = wind velocity, T = TORRO Tornado Intensity number, and B = Beaufort Force number.
References
Meaden G T, 1976, Tornadoes in Britain; their intensities and distribution in space and time, Journal of Meteorology, 1, 242-251.
http://www.torro.org.uk/tnintens.htm
