At approximately 10:00 PM on Friday, May 4th, the first ever EF 5 tornado left a path of destruction through Greensbug in south-central Kansas. This tornado stayed on the ground for 22 miles and was 1.5 miles wide at one point. When all was said and done, over 75% of the town was destroyed, 9 people lost their lives, and dozens were injured. Our storm chaser Darin Brunin was in Greensburg when the storm hit and compered the scene in Greensburg to the scene in the movie Twister when the town of Wakita was destroyed. An EF 5 tornado means that winds were in excess of 200 MPH. The last tornado to have winds in excess of 200 MPH was the infamous F5 tornado the rolled across Moore, OK and Oklahoma City in May of 1999. To put a little perspective on this, a category 5 hurricane has winds of 150 MPH. This storm will certainly go down in the history books.
Over the years, we have become familiar with the F scale, or Fujita Scale. So, whats the deal with this new EF scale and why did it change?
The new EF Scale, or Enhanced Fujita scale, is an upgrade on the old F scale. Remember, that there is no way to accurately measure the winds in a tornado, thus we do not measure tornadoes based on how fast the winds are blowing. We measure them based on how much damage a tornado does. The old F scale had been around for over 50 years, and in that time the construction of buildings has changed. So in order to accurately classify tornadoes, new criteria was needed.
Enter the Enhanced Fujita Scale.
The scale still has six levels, EF 0 through EF 5. Here is a chart of the new EF Scale and the approximate wind speeds.
RATING: Approx. Wind Speed
EF0 >85 MPH
EF1 86-110 MPH
EF2 111-135 MPH
EF3 136-165 MPH
EF4 166-200 MPH
EF5 >200 MPH
A second advantage that the Enhanced Fujita Scale has over the old F Scale is that it takes into account damage to vegetation. In the past if a tornado ripped across a cow pasture it may have only been rated a F1 because it didn't cause any damage. While if this tornado had gone through a town or city it may have caused damage and been a F3. With the EF scale a tornado should have the same rating no matter where it tracks.
Again, we can not measure the wind speeds in a tornado and can only approximate how fast winds need to blow to cause certain damage. The new EF scale is simply an improvement on the old F scale. It allows us to better classify these storms and that will ultimately lead to better and more accurate research and will help improve the warnings of tornadoes.