I think it’s time to throw the Fujita Scale out the broken window.
I get the idea. Estimate a tornadoes wind speed based on the damage it creates, the destruction it inflicts. It IS a good measurement of wind speed, but that’s all. As any storm chaser or tornado victim will tell you however, wind speed is only one part of the story. An important part indeed, but there are other parameters we can measure that I believe are as, if not more important. As it turns out, wind speed is just a slice of the sky.
With the Fujita/Enhanced Fujita scale there is a critical disconnect, a fly in the rubble so to speak. It has always troubled me that we can talk about F5, F2 and EF3 etc and infer that these ratings are absolutes. They are not.
Here is the case which got me thinking.
The Elie Manitoba F5 (Canada uses the Fujita Scale and not the Enhanced Fujita Scale like the United States) was an impressive tornado, destroyed a mill, swept several homes off their foundations, tossed a semi truck through the air and based on video and damage path evidence was given an F5 rating. Impressive wind speeds to be sure but here is what troubles me about Elie; Joplin. Joplin troubles me when compared to Elie because both tornadoes were given the same classification based on one small, tiny, weenie factor which was the truck that was tossed and the two homes that were removed from the earth.
Lets put this into perspective, Joplin was on the ground for 45 minutes and showed signs of F3-F5 damage along a path that was 25km long. At its peak it was close to 2km wide at the base and was travelling at 90km ground speed. It destroyed 8000 buildings, cost a billion dollars, killed over 150 people, decimated an entire city and there are reports of debris from the storm that travelled close to 200 miles. Elie, by contrast was a thin rope, travelled slowly, did relatively little damage and was not a costly natural disaster in terms of dollars or lives. These two storms/tornadoes are not even close to the same…Not Even Close.
So how should we measure tornadoes? I say we measure them like we would measure anything else.
The E-Scale. ‘E’ equals energy. The Energy Scale for Tornado classification is the solution and would be very easy for the general public to understand. Let’s look at all the factors that we can easily measure with any tornado.
1-Windspeed, This one is easy, we are already doing it. Its called the F/EF scale and it works as a measurement of wind speed in the absence of a scientific instrument measurement.
2- Scale or Width. How wide was the tornado. How broad based was the damage.
3- Length. Again, very easy to determine. Measure the width and multiply that by the length and voila you have a square metre/foot/ mile/km/ whatever that shows how much area was impacted by the cyclone.
4- Time. How long did it last. This is critical. A tornado that is on the ground for an hour is producing/expending a lot of energy.
Therefore, the E-Scale would be a very simple math problem. And it would look like this:
Energy=Wind + Scale + Length + Time
So let’s analyse the two sample F5 rated tornadoes and compare them using the E-scale:
- Elie, Manitoba: 350km x 100 x 6 x 40 = 8,400,000 or an E-scale rating of 8.4
- Joplin, Missouri: 350km x 1500 x 25 x 45 = 590,625,000 or an E-scale rating of 590.6
- Pipestone, Manitoba (the day after Elie): 250 x 1500 x 30 x 45 = 506,250,000 or an E-scale rating of 506.2
- Hattiesburg, Mississippi 2013: 270 x 1200 x 36 x 33 = 384,912,000 or and E-scale rating of 384.9
- Salina Kansas, April 14 2012: 300 x 500 x 65 x 50 = 487,500,000 or an E-Scale Rating of 487.5
- Rush Center Kansas, April 14 2012: 180 x 100 x 28 x 20 = 10,080,000 or an E-scale Rating of 10.0
- Moose Jaw, Saskatchewan June 26 2012: 200 x 100 x 1 x 20 = 400,000 or an E-scale rating of .4
When you see these results on the E-scale, they correlate very closely to our ‘experiential ‘ measurement and are much more accurate than a simple 0-5 classification. We look at Joplin and are shocked by the images, the video and the overall scale of the destruction. We watched the Pipestone video and thought…thank god that didn’t hit a populated area. And when we see a small tornado that lasts only a short time, no matter how bad the localized damage is at the base, we think…hmmm that wasn’t that bad. The E-scale is a much more realistic portrayal of a tornadoes impact and energy than the Fujita or enhanced fujita scale.
This is a video I shot of the damage at Joplin
Amazing video of the Elie Tornado. Although the destruction is incredible, note the scale of the destruction.
Bron: Tornadohunter Greg Johnson | Gewijzigd: 16 februari 2017, 12:31 uur, door Joyce.s