F6 Tornadoes-What's the Closest We've Come?

[Bill Tabor]

Since I just posted about the Fujita scale on wx-chase I repost it here as it pertains to what people are talking about:

It is interesting that comments and controversies regarding the F-scale commonly come up on this
list. I think many are confused or do not know what F-scale is. I think the best way for everyone to
understand what it is to see how it is derived. That may also provide more enlightenment or
appreciation while later reviewing tornado footage of a tornado's power after the damage was done and
it was rated.

The most straight forward way of looking at this, or describing it from what I can tell is F-scale is
really a pretty simple mostly conceptual - even somewhat arbitrary scale based on combining 12
different levels of force and relating those to Mach numbers (speed of sound at sea level) where
force 12 (highest force) is associated with Mach 1. The twelve point scale comes from the Beaufort
force (wind) which on it's own is not associated with Mach numbers. Fujita associated it with Mach
using a formula ((F) is V = 14.1 * ((F+2) to the 1.5 power)). Fujita then chopped off the upper seven
levels of force and only uses 0-5 F levels.

http://www.crh.noaa.gov/lot/webpage/beaufort/
http://lwf.ncdc.noaa.gov/oa/satellite/sate...nal/fujita.html

The scale has been adopted and is used to describe a 'level' of damage incurred from a tornado. Since
F-scale is derived from wind speeds using Mach numbers it is therefore related to windspeeds although
those would therefore be to a certain degree arbitrary and not necessarily close to those in the
actual tornado. This is also because the scale chosen for a tornado is based on somewhat subjective
analysis of damage (i.e. thrown cars versus peeled asphalt, etc) in order to associate it with a
particular range.

Still I wonder how accurate F-scale would be (based on damage done) as a predictor of the associated
wind speed? I wonder if Fujita took any dynamic forcing or pressure effects as seen in tornadoes into
consideration? Since he created the formula and applied it to the ranges rather than just equally
dividing Mach 1 into twelve equal segments it seems he had something in mind and apparently this
formula fit some of his experimental observations.

Others have any thoughts here?

 

[Bill Tabor]

Also in regard to the original question I believe Fujita limited the official F-scale to F5. Damage levels over F5 were to be rated F5 because most didn't think it would be possible to distinguish between damage done above those levels. The Beaufort scale goes up to twelve levels that the F-scale is based on.

 

[Shane Adams]

Yes, that could be taken to mean something negative...

But I think I've gone out of my way to express that, under no circumstance, do I ever which destruction or harm upon anything/anyone. However, because you yourself made the disticntion between the "rated" F5 tornado and an "F5 caliber" tornado (to say the winds are over 260mph) it made more sense to describe my desire to see an F5 tornado in a way which incorporates the damage aspect, because that's what most who follow weather relate to.

I can't make people understand what I mean on here anymore, it's getting too intimate. I need a room and real faces, real people.

This screen and these keys just don't convey it the way it is

 

[Glen Romine]

This screen and these keys just don't convey it the way it is

Excellent point - I'm sure many facial expressions would have instantly hinted to you the ack! syndrome, and this could have been nipped a long time ago. I for one vote we let this thread go into retirement and find a lighter subject to muse over.

Glen

 

[Shane Adams]

Originally posted by Mike Peregrine
Interestingly enough, though - it's amazing how many people after a big event DO want photos/video of a tornado that affected them somehow ... after May 29th I had like three requests from people in Kansas - one of which's father's home was badly damaged by the Jamestown tornado - who wanted more pics and video from the event. It happens that I actually got a shot of this victim's father's place in there. The same thing happened after May 4th last year with some friends of mine who lost their home completely ... they wanted to see what hit them from the other side!

It's actually part of the healing process, I think ... not uncommon at all - -

The day after the June 12 Mulvane tornado, while we were on site doing a damage survey, the owner of the home (Mrs) that was destroyed southeast of town watched Dave's video of the tornado hitting her house several times; she was calling friends and relatives to come over and watch with her. By the time we left that day, I had a list of addresses from people who wanted copies of the video.

 

[Pete Johnson]

What has happened to the days of wanting to see one of the rarest meteoroligcal phenomenoms? We now need to see various classifications of them?!? I did not hear many chasers complaining that the famous Throckmorton tornado April 7, 2002 was not rated an F5. When I go out chasing, I hope for a supercell capable of producing a tornado in the open plains. I'll agree with Glen that the last thing on my mind, even after a chase, is the rating. Even for nostalgic purposes, most chasers don't refer to specific tornadoes using the F-scale. "Did you see the Argonia wedge? Where were you for the Happy, TX tornado?" I personally have no desire to see an F5 (not saying that I will never see or chase one). A 1/2 mile wedge or even a 100 yard wide rope or in open country will make me 100 times happier than recalling the day I saw the Dallas - Fort Worth metro get destroyed (praying that it never happens).

 

[Shane Adams]

I guess I'm fortunate in that I saw the F5, but didn't witness it tear through OKC. We were on it when it formed, which was in open country, so from our angle, it wasn't a threat to life or property. So for the short while we were on it, we were able to enjoy it. Once we realized it wasn't going to stop and was heading into OKC, we abandoned the storm.

We did not want to see what it was going to do.

 

[Shane Adams]

I understand I'm not in control of a tornado's damage, but I have no desire to follow one through a town while it's doing major destruction. I'm not trained in emergency assistance, and if I was to happen upon damage, I would have to stop and render aid......something I'm not experienced at.

So, the best role I can play in this situation is to break off the tornado, stay away from the damaged areas so people who do have rescue experience can do their jobs without someone like me interfering. My experience lies in observing and reporting severe weather, which can help prevent the injuries and death, so that's the route I take in situations like May 3, 1999.

 

[Charles Kuster]

And herein lies the confusion: I say "F5" when I think of winds in a tornado being over 260mph, not a neighborhood full of clean slabs. I'm one of the (apparently) few people who are willing to look at the estimated windspeed numbers next to each lil level on the F-scale chart and say "why not?"

So no, when I say "I want to see an F5" I do not mean I want to see devastation.....rather, just a good old-fashioned violent tornado like everyone else and their purple pooch :wink:

[/quote]


I agree with Shane. I would like to see an F5. However, that does not mean that I want to see someone's house destroyed. It just means that I want to see a strong tornado. I would prefer to see a tornado over open country than go through a town. Who wouldn't? I also look at the wind speeds on the Fujita scale. For me, I would like to see a tornado not hit anything, but it had winds over 260mph. I would consider this an F5 whether it damaged something or not. It may not be a true F5, but was a very strong tornado and it did not hurt anyone. 8)