As the temps get warmer and we put winter in the rear view mirror, it's time for spring, and severe weather season! So lets take some time to talk about what some see as the most interesting part of severe weather season, tornadoes.
To start I must talk about Dr. Ted Fujita. During the 1950s and 60s Dr. Fujita, a professor at the University of Chicago, studied the damage created by tornadoes across various parts of the country. From those studies he created the original scale for assessing the strength of a tornado. This is that chart below, the Fujita Scale.
You'll notice that the strength of a tornado is categorized by both a wind speed and damage. In most cases tornado winds cannot be measured directly, so the rating of a tornado is determined by assessing the worst damage it produces. When a tornado is reported, the National Weather Service(NWS) will send out a crew of meteorologists to diagnose the damage and assign the tornado a EF Scale rating. What they are looking for is many of the things Dr. Fujita pointed out in his original studies. Damage to houses, trees, mobile homes and cars are some of the things they will look at.
In February of 2007, the NWS revised from the original Fujita Scale to reflect better examinations of tornado damage in order to align wind speeds more closely with associated storm damage. Here is that scale, the Enhanced Fujita Scale.