F1 Tornado
An F1 tornado is considered a "weak" tornado. In the original F Scale, F1 tornadoes were estimated to contain winds with maximum speed of between 73 and 112 MPH and a maximum 3-second wind gust speed of 79 to 117 MPH. The EF Scale changes the maximum 3-second gust speed to between 86 and 110 MPH. Descriptively, an F1 tornado causes moderate damage including any or all of peeling surface materials off of roofs, pushing mobile homes from their supports, lifting and moving vehicles from roads and severely damaging attached garages. Winds with velocity of at least 73 MPH are considered hurricane winds.
F2 Tornado
An F2 tornado, termed a "strong" tornado, contains winds moving at higher speed and therefore has the potential to cause more severe damage than an F1 tornado. In the original F Scale, F2 tornadoes were estimated to contain winds with maximum speed of between 113 and 157 MPH with a maximum 3-second wind gust speed of 118 to 161 MPH. The EF Scale changes the maximum 3-second gust speed to between 111 and 135 MPH. Descriptively, an F2 tornado causes considerable damage. The storm can tear roofs from houses, demolish mobile homes, snap or uproot trees and turn lighter objects into missiles capable of penetrating solid surfaces.
Stronger Storms
The F Scale continues to F5, the "incredible" tornado. F5 tornado winds are estimated to reach sustained speeds of 261 to 318 MPH, causing severe damage to steel-reinforced concrete structures and turning cars into air-borne missiles. Fortunately, less than 1 percent of tornadoes reach the level of F4. As of 2010, the three most recent F5 tornadoes in the USA occurred in Parkersburg, Iowa (May 25, 2008), Greensburg, Kansas (May 4, 2007), and Moore and Bridge Creek, Oklahoma (May 3, 1999).
Wind Estimates
Meteorologists caution the public that the wind speeds cited in the F and EF Scales are only estimates that have not been verified by direct measurements. Wind speed is just one variable to consider when assessing damage. Other variables include the quality of the construction and the shape of the terrain near the site where a storm touches down. Given different conditions, it is possible for the same storm with the same wind speed to cause different levels of damage at two different locations.