Geoscience Reference
In-Depth Information
Table 7.3 TORRO scale parameters
FI
v, m/s
Tornado description
Intensity
description
Damage description
FC
Funnel cloud aloft (not
a tornado)
Weak
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
F0
17 - 24
Light
Loose light litter raised from ground level in spirals
Tents, marquees, awnings seriously disturbed
Some exposed tiles, slates on roofs dislodged. Twigs
snapped; trail visible through crops
Wheelie bins tipped and rolled
Garden furniture and pots disturbed
Deck chairs, small plants, heavy litter becomes
airborne
Minor damage to sheds
More serious dislodging of tiles, slates
Chimney pots dislodged. Wooden fences flattened
F1
25 - 32
Mild
Slight damage to hedges and trees
Some windows already ajar blown open breaking
latches
F2
33 - 41
Moderate
Heavy mobile homes displaced. Light caravans blown
over
Garden sheds destroyed. Garage roofs torn away and
doors imploded
Much damage to tiled roofs and chimneys. Ridge tiles
missing
General damage to trees, some big branches twisted or
snapped off, small trees uprooted
Bonnets blown open on cars
Weak or old brick walls toppled
Windows blown open or glazing sucked out of frames
F3
42 - 51
Strong
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
Some heavier debris becomes airborne causing
secondary damage breaking windows and impaling
softer objects
Debris carried considerable distances. Garden walls
blown over
Eyewitness reports of buildings physically shaking
Mud sprayed up the side of buildings
Motorcars 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
F4
52 - 61
Severe
Strong
Numerous trees uprooted or snapped. Traf
c Signs
folded or twisted
(continued)
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