National Weather Service United States Department of Commerce

Heavy rain across the eastern U.S.

Low pressure will weaken some as it heads to the Northeast U.S. tomorrow, but still will be capable of producing areas of heavy rain from the Mid-Atlantic to New England. Severe thunderstorms are possible in the central Plains and Lower Mississippi Valley over the next couple of days. More widespread severe storms are possible in the southern Plains by the end of the week. Read More >

 Enhanced Fujita Scale
EF-scale Class Wind speed Description
mph km/h
EF-0 weak 65-85 105-137 Gale
EF-1 weak 86-110 138-177 Moderate
EF-2 strong 111-135 178-217 Significant
EF-3 strong 136-165 218-266 Severe
EF-4 violent 166-200 267-322 Devastating
EF-5 violent > 200 > 322 Incredible

The Fujita (F) Scale was originally developed by Dr. Tetsuya Theodore Fujita to estimate tornado wind speeds based on damage left behind by a tornado. An Enhanced Fujita (EF) Scale, developed by a forum of nationally renowned meteorologists and wind engineers, makes improvements to the original F scale. This EF Scale has replaced the original F scale, which has been used to assign tornado ratings since 1971.

The original F scale had limitations, such as a lack of damage indicators, no account for construction quality and variability, and no definitive correlation between damage and wind speed. These limitations may have led to some tornadoes being rated in an inconsistent manner and, in some cases, an overestimate of tornado wind speeds.

The EF Scale takes into account more variables than the original F Scale did when assigning a wind speed rating to a tornado. The EF Scale incorporates 28 damage indicators (DIs) such as building type, structures, and trees. For each damage indicator, there are 8 degrees of damage (DOD) ranging from the beginning of visible damage to complete destruction of the damage indicator. The original F Scale did not take these details into account.

For example, with the EF Scale, an EF3 tornado will have estimated wind speeds between 136 and 165 mph (218 and 266 kph), whereas with the original F Scale, an F3 tornado has winds estimated between 162-209 mph (254-332 kph). The wind speeds necessary to cause "F3" damage are not as high as once thought and this may have led to an overestimation of some tornado wind speeds.