Fujita scale

The Fujita scale rates a tornado's intensity by the damage it inflicts on human-built structures. It was introduced in 1971.

The categories are as follows:

Table of contents 1 F0 <73 mph (<115 km/h) 2 F1 73-112 mph (116-180 km/h) 3 F2 113-157 mph (181-250 km/h) 4 F3 158-206 mph (251-330 km/h) 5 F4 207-260 mph (331-415 km/h) 6 F5 261-318 mph (416-510 km/h)

F0 <73 mph (<115 km/h)

Light damage. Some damage to chimneys; branches broken off trees; shallow-rooted trees pushed over; sign boards damaged.

F1 73-112 mph (116-180 km/h)

Moderate damage. Peels surface off roofs; mobile homes pushed off foundations or overturned; moving autos blown off roads.

F2 113-157 mph (181-250 km/h)

Considerable damage. Roofs torn off frame houses; mobile homes demolished; boxcars overturned; large trees snapped or uprooted; light-object missiles generated; cars lifted off ground.

F3 158-206 mph (251-330 km/h)

Severe damage. Roofs and some walls torn off well-constructed houses; trains overturned; most trees in forest uprooted; heavy cars lifted off the ground and thrown.

F4 207-260 mph (331-415 km/h)

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

F5 261-318 mph (416-510 km/h)

Incredible damage. Strong frame houses leveled off foundations and swept away; automobile-sized missiles fly through the air in excess of 100 meters (109 yds); trees debarked; incredible phenomena will occur.

Note that wind speeds empirically derived from engineering data from damage surveys can only be approximate, but highly reliable. While wind speeds verified with high resolution doppler radar (better than Nexrad), return accurate wind speeds and accurate Fujita scale ratings. Tornadoes with an intensity greater than F5 are commonly regarded as F5. Mostly due to the fact that the theoretical maximum potentential of variables of the atmosphere may have an upper limit at F5. Also note that a hypothetical F12 would correspond to Mach 1, i.e. the speed of sound.

• External link: http://www.spc.noaa.gov/faq/tornado/f-scale