Category
F0: Gale
tornado (40-72 mph); light damage. Some damage to chimneys; break
branches off trees; push over shallow-rooted trees; damage to
sign boards.
Category
F1: Moderate
tornado (73-112 mph); moderate damage. The lower limit is the
beginning of hurricane wind speed; peel surface off roofs; mobile
homes pushed off foundations or overturned; moving autos pushed
off the roads.
Category
F2: Significant
tornado (113-157 mph); considerable damage. roofs torn off frame
houses; mobile homes demolished; boxcars pushed over; large trees
snapped or uprooted; light-object missiles generated.
Category
F3: Severe
tornado (158-206 mph); Severe damage. Roofs and some walls torn
off well-constructed houses; trains overturned; most trees in
forest uprooted; heavy cars lifted off ground and thrown.
Category
F4: Devastating
tornado (207-260 mph); Devastating damage. Well-constructed houses
leveled; structure with weak foundation blown off some distance;
cars thrown and large missiles generated.
Category
F5: Incredible
tornado (261-318 mph); Incredible damage. Strong frame houses
lifted off foundations and carried considerable distance to disintegrate;
automobile sized missiles fly through the air in excess of 100
yards; trees debarked; incredible phenomena will occur.
