MEMPHIS, Tenn. (WMC) - The National Weather Service uses a scale from zero to five to rate a tornado, all done after assessing the damage inflicted by the twister. This scale is called the Enhanced Fujita Scale which has been used in some form or fashion since 1971.
The original Fujita scale was developed by a man named Dr. Ted Fujita. Fujita developed the scale to provide a wind estimate for the amount and type of damage that occurred from a tornado.
In 2007, a group of renowned meteorologist and wind engineers made improvements to the original scale which made improvements on how the wind speeds were estimated.
The National Weather Service will survey damage after the tornado has passed, looking at various indicators such as trees, building types and structures.
There are various degrees of damage staring with visible damage to complete structure destruction, which under the original Fujita Scale didn’t consider.
The National Weather Service will survey the damage as soon as they can and usually takes one to two days after the event to gain a preliminary rating. Even longer if it is a multiple tornado outbreak.