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The Tornado and Storm Research Organisation (TORRO) was founded by Terence Meaden in 1974. Originally called the Tornado Research Organisation it was expanded in 1982 following the inclusion of the Thunderstorm Census Organisation (TCO) after the death of its founder Morris Bower and his wife. The current Head of TORRO is Paul Knightley, a professional meteorologist.

TORRO comprises nearly 400 members in the United Kingdom and others from around the world, from amateurs to professional meteorologists, and almost 30 staff. TORRO maintains a large storm spotter network throughout the British Isles and collects and records reports of severe weather.

TORRO carries out research on many aspects of severe weather including ball lightning, blizzards & heavy snowfall, coastal impacts, hailstorms, lightning impacts, tornadoes, thunderstorms, weather disasters, and weather & health.

Tornadoes in the UK are classified using the T-scale. TORRO has also developed a hailstorm intensity scale.[1]

TORRO publishes the semi-professional periodical the International Journal of Meteorology (IJMet) which is composed of a mixture of academic and amateur articles.

The 12 categories for the TORRO scale are listed below, in order of increasing intensity. Although the wind speeds and photographic damage examples are updated, which are more or less still accurate. However, for the actual TORRO scale in practice, damage indicators (the type of structure which has been damaged) are predominately used in determining the tornado intensity.

Scale Wind speed
(Estimated)
Potential damage Example of damage
mph km/h m/s
FC - - - No damage. (Funnel cloud aloft, not a tornado)

No damage to structures, unless on tops of tallest towers, or to radiosondes, balloons, and aircraft. No damage in the country, except possibly agitation to highest tree-tops and effect on birds and smoke. Record FC when not known to have reached ground level. A whistling or rushing sound aloft may be noticed.

T0 39 - 54 61 - 86 17 - 24 Light damage.

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 55 - 72 87 - 115 25 - 32 Mild damage.

Deckchairs, small plants, heavy litter becomes airborne; minor damage to sheds. More serious dislodging of tiles, slates, chimney pots. Wooden fences flattened. Slight damage to hedges and trees.

T2 73 - 92 116 - 147 33 - 41 Moderate damage.

Heavy mobile homes 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 93 - 114 148 - 184 42 - 51 Strong damage.

Mobile homes overturned / badly damaged; light caravans destroyed; garages and weak outbuildings destroyed; house roof timbers considerably exposed. Some of the bigger trees snapped or uprooted.

T4 115 - 136 185 - 220 52 - 61 Severe damage.

Motor cars levitated. Mobile homes airborne / destroyed; sheds airborne for considerable distances; entire roofs removed from some houses; roof timbers of stronger brick or stone houses completely exposed; gable ends torn away. Numerous trees uprooted or snapped.

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T5 137 - 160 221 - 259 62 - 72 Intense damage.

Heavy motor vehicles levitated; more serious building damage than for T4, yet house walls usually remaining; the oldest, weakest buildings may collapse completely.

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T6 161 - 186 260 - 299 73 - 83 Moderately - devastating damage.

Strongly built houses lose entire roofs and perhaps also a wall; windows broken on skyscrapers, more of the less-strong buildings collapse.

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T7 187 - 212 300 - 342 84 - 95 Strongly - devastating damage.

Wooden-frame houses wholly demolished; some walls of stone or brick houses beaten down or collapse; skyscrapers twisted; steel-framed warehouse-type constructions may buckle slightly. Locomotives thrown over. Noticeable de-barking of trees by flying debris.

T8 213 - 240 343 - 385 96 - 107 Severely - devastating damage.

Motor cars hurled great distances. Wooden-framed houses and their contents dispersed over long distances; stone or brick houses irreparably damaged; skyscrapers badly twisted and may show a visible lean to one side; shallowly anchored highrises may be toppled; other Steel-framed buildings buckled. (2008 Poland tornado outbreak, for example)

T9 241 - 269 386 - 432 108 - 120 Intensely - devastating damage.

Many steel-framed buildings badly damaged; skyscrapers toppled; locomotives or trains hurled some distances. Complete debarking of any standing tree-trunks.

T10 270 - 299 433 - 482 121 - 134 Super damage.

Entire frame houses and similar buildings lifted bodily or completely from foundations and carried a long or large distance to disintegrate. Steel-reinforced concrete buildings may be severely damaged or almost oblilerated.

T11 >300 >483 >135 Colossal damage.

Strong framed, well built houses leveled off foundations and swept away, steel-reinforced concrete structures are critically damaged, tall buildings collapse or have severe structural deformations, some cars, trucks and train trucks can thrown approximately 1 miles (1.6 kilometres).

The exact meteorological conditions to create a tornado of this magnitude rarely exist in Europe. The United States is one of the few places on Earth that can have such a storm. An example of a T11 tornado would be the Joplin tornado or the Hackleburg tornado.
T0 T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11
Weak Strong Violent