Intensity Phrase

Wind Speed(mph)

Type of Damage Done

 
W
E
A
K

F0

Gale tornado

40-72

Some damage to chimneys; breaks branches off trees; pushes over shallow-rooted trees; damages sign boards.

F1

Moderate tornado

73-112

The lower limit is the beginning of hurricane wind speed; peels surface off roofs; mobile homes pushed off foundations or overturned; moving autos pushed off the roads; attached garages may be destroyed.

S
T
R
O
N
G

F2

Significant tornado

113-157

Considerable damage. Roofs torn off frame houses; mobile homes demolished; boxcars pushed over; large trees snapped or uprooted; light object missiles generated.

F3

Severe tornado

158-206

Roof and some walls torn off well constructed houses; trains overturned; most trees in fores uprooted

V
I
O
L
E
N
T

F4

Devastating tornado

207-260

Well-constructed houses leveled; structures with weak foundations blown off some distance; cars thrown and large missiles generated.

F5

Incredible tornado

261-318

Strong frame houses lifted off foundations and carried considerable distances to disintegrate; automobile sized missiles fly through the air in excess of 100 meters; trees debarked; steel re-inforced concrete structures badly damaged.

F6

Inconceivable tornado

319-379

These winds are very unlikely. The small area of damage they might produce would probably not be recognizable along with the mess produced by F4 and F5 wind that would surround the F6 winds. Missiles, such as cars and refrigerators would do serious secondary damage that could not be directly identified as F6 damage. If this level is ever acheived, evidence for it migh only be found in some manner of ground swirl pattern, for it may never be identifiable through engineering studies