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

I've heard that the Fujita scale has an F6 classification, which is for tornaodes with winds past 318 miles an hour. What tornadoes have come close to hitting this? I was wondering if the 1991 (?) Andover Kansas tornado was anywhere in this vicinity; I remember reading that its winds were over 300 mph.
 
Tornadoes I have read that were very strong F-5's

March 18 1925: Tri-state" Tornado
April 09 1947: Woodward OK Tornado
April 03, 1974: Xenia OH Tornado (came close from what I have heard)
April 26 1991: Andover KS Tornado
May 03, 1999: Bridge Creek, Moore OK Tornado

Mike
 
I'd guess most scientists and engineers would say "never," since most of them don't believe any F-scale winds are correct. F6 tornadoes could never be identified in a damage survey (because F5 winds obliterate everything and remove debris), therefore the F6 is a contradiction to its own scale, which is based solely on destruction.
 
The "F" scale actually goes up to F12... F6 or greater was never expected to be reached, so it isn't commonly shown on most scales. Since the "F" scale is purely a damage scale, and F5 is the worst damage you can have (everything swept away), it would be near impossible to reach F6 damage...
 
Well what if just don't only obliterate the house... but also dig a trench along it's path?

Well, if that tornado that digs a trench doesn't hit any structures or trees, it would be rated probably no higher than F0, because it caused no damage.

Put that same tornado over a town, and it wipes out everything, it would probably be an F5, or maybe what some would call a strong F5. Once the house is swept away (which F5 winds will do), the tornado can't do any more damage to it, leaving it at an F5 rating...
 
I'd guess most scientists and engineers would say "never," since most of them don't believe any F-scale winds are correct. F6 tornadoes could never be identified in a damage survey (because F5 winds obliterate everything and remove debris), therefore the F6 is a contradiction to its own scale, which is based solely on destruction.

So-why bother having this F6 classification then? Was there a reason for Mr. Fujita to have classifications from F6 on up?

:?
 
I remember someone on an Oklahoma City news channel say that one of the D.O.W. trucks close to Bridgecreek on I-44 near the toll gate registered the May 3, 1999 tornado at 321mph for a very brief moment which would have made it an F6 tornado. They talked about it a little on the news but then dropped the topic a few days later. I believe an F6 is possible but it would have to annihilate everything (steel posts, billboard poles, bridges, etc..) in its path before anyone would believe it.
 
318 mph was measured

I have a video tape of that May 3, 1999 F-5 Oklahoma City tornado. The back of the box and the tape itself said they had a Doppler on Wheels tracking that storm. It measured 318 mph at one point. Too bad the F scale measures by damage alone, not the wind speed. If we ever go to the wind speed scale instead of the damage scale, then the OK City tornado would stand as a true F-6 class storm. 8)
 
He didn't make an F6... He took the speed of sound, divided it by 12 and then associated damage with each interval. Since F5 was total destruction, there was no way to have anything higher. The wind speeds are just esimates, and all scientific studies shows they may be overrated.

- Rob
 
Yeah, DOW did measure 318 mph winds, I was going to bring that up, however the winds were measured higher up in altitude, so the surface winds were likely less than this.

Andrew Pritchard
 
There are structures, such as steel-reinforced concrete overpasses and parking garages, that can withstand F5, so hypothetically you can build things that, if hit by an uber tornado, might be able to measure damage caused by winds higher than F5 level. The trick is getting lucky enough to actually have something that powerful actually hit something designed to measure it. Talk about needle in a haystack.

I want to nominate the Mulhall tornado from May 3, 99. I have heard from a few people that it was doing things along its damage path that they had never seen before, but which didn't fit into standard classifications, so it only got an F4, but it may have been bigger than the Moore tornado.
 
I'd guess most scientists and engineers would say "never," since most of them don't believe any F-scale winds are correct. F6 tornadoes could never be identified in a damage survey (because F5 winds obliterate everything and remove debris), therefore the F6 is a contradiction to its own scale, which is based solely on destruction.

So-why bother having this F6 classification then? Was there a reason for Mr. Fujita to have classifications from F6 on up?

:?

I've been asking that question for years......... :roll:
 
Yeah, DOW did measure 318 mph winds, I was going to bring that up, however the winds were measured higher up in altitude, so the surface winds were likely less than this.

Andrew Pritchard

Interestingly though, one particular instance that was used as an example of "evidence" that F-scale winds are too high was this same day, where the DOWs measured windspeeds of only 200mph in the same areas where survey teams labled F5 damage.

So why is a 318mph measurement taken with a grain (and widely, generally scoffed at in the science world) while the lesser, more "tame" 200mph measurement is used as evidence against the current suggested speeds associated with the F-scale? Are DOW measurements taken seriously or not? Depends :wink:

It's all politics. Some time back, scientists decided the winds were too high, so now every "finding" will point to exactly that.
 
One of the most important things to remember in considering the 318mph DOW measurement is elevation! Since that radar was scanning at an elevation >0 (it was ~0.5degrees I think), the farther from the radar one gets, the higher the radar beam is (relative to the ground). Because of this, the DOWs measured the wind (by radar) a couple of hundred feet above the surface. Since friction reduces surface wind speeds, the actual wind at the surface was likely a little less than 318. Whatever the case, it was still in the F5 range by wind estimation, which doesn't officially matter anyways...

From a FAQ on the NWS OUN website:
"Q: Was the Bridge Creek/OKC area tornado on May 3, 1999, rated F6?

A: No. The tornado has been rated F5 (minimal F5, in fact), and will not be "upgraded" to F6. There was some speculation in the media of an F6 rating after "Doppler on Wheels" (DOW) researchers from the University of Oklahoma announced that their radar measured 318-mph winds in the tornado while it was near Bridge Creek. However, the jump in reasoning to rating this tornado F6 can not be made, for many reasons:

F-scale ratings are assigned based on the severity of the damage caused, *not* on wind speed. Although some of the damage was incredible (as it is with any F5 tornado), the most severe damage from the May 3 tornado was comparable to, but not worse than, other documented F5 tornadoes.

Wind speeds used in the F scale have not been scientifically calibrated to the severity of damage that defines each F scale level. They are, essentially, only estimates.

Even if the F-scale wind speed ranges were reliable estimates, the DOW measurement of 318 mph is still in the F5 range (261-318 mph) as defined by Dr. Fujita.

The data obtained by the DOW team are still in the process of being reviewed scientifically, and so the validity of the 318-mph wind measurement is still open to some question at this point. Early results of this review process suggest that the maximum speed actually may be less than 318 mph (although it likely will remain above 300 mph).

The 318-mph wind measurement was obtained at a height of about 50 to 100 meters (160 to 320 feet) above the ground. Since winds typically decrease as you get closer to the ground, wind speeds at the ground (where the damage was done) would have been less.

In reality, there is no such thing as an F6 tornado. When Dr. Fujita developed the F scale, he created a scale that ranges from F0 to F12, with estimated F12 winds up to mach 1 (the speed of sound). But he added that "tornadoes are not expected to reach F6 wind speeds." This leaves only the F0 to F5 range as the actual tornado F scale. For a tornado to be given an unprecedented F6 rating, it would have to produce damage more severe than has ever been observed. As stated above, there was nothing unusual or unprecedented in the damage from the May 3 tornado as compared with other F5 tornadoes in the past."
---> http://www.srh.noaa.gov/oun/storms/1999050...3/may3faqs.html

{I'm posting this in an extended form since it was public information, available to the general public on a government website. As such, there should be no "3rd Party" issues to deal with here}
 
Shane,

I'm actually not aware of a DOW velocity to damage survey having been done for the May 3 case (do you have a link?) - though one was done for the Spencer, SD 1998 storm. Since the measurements are taken well off the ground, with a very short in time sampling interval, taking into account much of the signal is from flying debris and vertical alignment issues - a lot of modification is required to infer what wind speeds might be at ground level. Nevertheless, the Spencer study actually had relatively good agreement between the 'measured' and observed damage - at least by scientist standards.

Yes, there is a growing audience of engineers and meteorologists that stress the difficulty in damage assessment - as the structural integrity of one home within a community is only as good as the weakest home - as that home becomes flying debris that impacts the neighbor and weakens the structure. If the intensity of the May 3 tornado as it moved through Moore had been in an area with fewer structures - there may have been fewer missles, and perhaps the level of damage inflicted would have been less. It is a very difficult problem to estimate the winds that will cause a particular structure to fail - but even harder to know how it will hold up to being bombarded with debris at the same time. Home construction differences opens a real can of worms regarding the home's vulnerabilities - as well as the orientation of the home to the strongest winds - duration of strongest winds - rate of wind acceleration - did the winds peak once or twice, if twice the difference in angle, etc.... So yes - lots of concerns about the current rating system - but I think it is shy of a conspiracy theory. There is, however, a lot of pressure on assessment teams to rate damage 'higher' when personal injury/loss enters the picture - so maybe some politics there.

Glen
 
I think there is too much focus on the wrong part of the story here. Who cares about the scale? The scale is relative, because when damage assesments are done, how buildings were built comes into play. It's pretty relative: "F5" damage to a house built in 1910 would probably be "F3" or "F4" damage to a house today.

On a separate note, I don't see why people are always in a fuss to get a rating on the tornado (and try to get the highest rating possbile at that). Wake up, the thing destroyed property and possibly injured or killed people...who cares what the rating is then?
 
I think people want to see the Moore, OK be rated higher than F5 since it has happened in such a modern age... with such better equipment.

Like that story said above, their is NOTHING different about the 5-3-99 tornado from all other "strong" F5 tornadoes. But, if it happened 75 years ago... probley 200+ people would have been killed.

Doesn't everybody agree that it will almost be impossible for a tornado to take 100+ lives in such a modern age? I forgot the total count... how many fatalities came from the 5-3-99 tornado?
 
Doesn't everybody agree that it will almost be impossible for a tornado to take 100+ lives in such a modern age? I forgot the total count... how many fatalities came from the 5-3-99 tornado?

Absolutely not! I think it would be quite easy to kill, oh, 2000 folks. Put the Bridgecreek / Moore OK F5 through the heart of Dallas/Fort Worth Metroplex... More even if it were during rush hour... I think a signficant tornado hitting any urban, downtown area could potentially cause a ton of fatalities. Of course, this isn't a guarentee, seeing how Moore and southern OKC survived an F4 last year without a single death! However, it's generally agreed that a signficant tornado, through downtown D/FW, and it's a bad bad thing...
 
Even with all the warning time for most significant tornadoes?

DTX did a little graph showing what if a F5 went through modern-day Detroit...

59d797f2f567d7219feb189ecf1f1085.gif

If that were to happen... a F5 would destroy my house! :shock:
 
Even with all the warning time for most significant tornadoes?

DTX did a little graph showing what if a F5 went through modern-day Detroit...

59d797f2f567d7219feb189ecf1f1085.gif

If that were to happen... a F5 would destroy my house! :shock:

Yep, thats the 1953 Flint F5 (the last deadliest tornado in US history), superimposed over Detroit.
 
I think the amount of tornado related deaths is determined by the area the tornado strikes. If a tornado were to strike Metro Dallas during rush hour, I dont believe those people would just sit in there cars and watch the twister barrel straight through the city. They will find shelter cause i believe in a way, we here in the cenral and southern plains have been "conditioned" to know what to do during a tornado warning. We know that we must seek shelter. The public is being better informed about weather and information moves much quicker allowing for a faster response. Something must be working since the amounts of deaths are declining (http://www.nssl.noaa.gov/users/brooks/publ...ml/deathtrivia/). But when we look at the southeast states particularly we see a less prepared community (http://www.disasterrelief.org/Disasters/02...22tornadostudy/) and a larger chance for massive tornado related deaths. I have also heard of a diference in how the public takes the appearance of a tornado in the southeast states, but have nothing to cite on it (as stated by my Professor). Of coarse i may be giving to much credit.
I do believe an F6 could occur but , since the Fujita Scale is a damage scale and the suggested wind speeds should not be set in stone, after an F5 there really isnt anything left for the tornado to damage I dont believe we can ever officially classify a tornado as an F6.
 
Even with all the warning time for most significant tornadoes?

If that were to happen... a F5 would destroy my house! :shock:

Yes, simply because there is no physical, realistic way to tell a couple million people to get below ground. This would be especially catastrophic if it occurred near rush-hour, when stopped-traffic would be sitting duck for a signficant tornado... For those interested, the NCTCOG did a rather extensive modeling study of what would happen should the Moore F5 trek through the DFW area... You can view it at http://www.nctcog.org/weather/study/index.asp ...
 
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