Category FO-- Gale Tornado Category 40 - 72 mph--
Light damage: some damage to chimneys, breaks branches off trees, pushes
over shallow-rooted trees, and damages sign boards.
Category F1-- Moderate Tornado Category 73 - 112 mph--
Moderate damage: The lower limit Category 73 mph-- is the beginning of hurricane
wind speed, peels surfaces of roofs, mobile homes pushed off foundations
or overturned, and moving autos pushed off roads.
Category F2-- Significant Tornado Category 112 - 157 mph--
Considerable damage: Roofs torn off the frames of houses, mobile homes demolished,
boxcars pushed over, large trees snapped or uprooted, and heavy cars lifted
off ground and thrown
Category F3-- Severe Tornado Category 158 - 206 mph--
Severe damage: Roofs and some walls torn off well-constructed houses, trains
overturned, most trees in forest uprooted, and heavy cars lifted off ground
and thrown.
Category F4-- Devastating Tornado Category 207 - 260 mph--
Devastating damage: Well-constructed houses leveled, structures blown off
weak foundations, and cars and other large objects thrown about.
Category F5-- Incredible Tornado Category 261 - 318 mph--
Incredible damage: Strong frame houses are lifted off foundations and carried
a considerable distance and disintegrated, automobile sized missiles fly
through the air in excess of 100 meters, and trees debarked.
Category F6+-- Inconceivable Tornado Category 319 - 379 mph--
The maximum wind speed of tornadoes is not expected to reach the F6 wind
speeds.
Tornadoes can be classified into one of three types:
Weak Tornadoes Category F0/F1-- These tornadoes account for 74% of all tornadoes.
They cause less than 5% of tornado deaths. Their lifetime is usually 1 -
10+ minutes with wind speeds less than 113 mph.
Strong Tornadoes Category F2/F3-- These tornadoes account for 25% of all tornadoes.
They cause nearly 30% of all tornado deaths and may last 20 minutes or longer.
Their wind speeds are clocked between 113 and 206 mph.
Violent Tornadoes Category F4/F5-- These rare tornadoes account for less than 2%
of all tornadoes. However, they cause 67% of all tornado deaths nationwide.
They may last for one hour or more with wind speeds greater than 206 mph.
