Is there such a thing as an F6?

[iowahawkeyedave]

Sorry for the noob question, and if it's been asked before. I've just been thinking about this question for a while, and I figured this would be the best place to ask it. The only reason I ask his is because I know the Moore F5 tornado had winds of 318mph, and at the time the scale went from 261-318 for F5. Now with the new scale, the threshold to achieve an EF5 is 200mph, yet the measured speed is still 318mph. It just seemed to me like there's quite a large difference (118mph) between the threshold for EF5 and the measured wind speed of 318mph, such that it would warrant adding additional EF values to accommodate the higher confirmed wind speeds.

Thanks in advance, and sorry once again if this has been asked before.

Dave

[matthewweatherwatcher]

I heard the f scale was made to go up to f12, so yes.

But a f5 and f6 damage would look so much the same that they could not tell the difference. Unless of course the twister hit a steal building of a major city then I believe that you could find out then, but I doubt they would do it even then.

http://www.tornadoproject.com/fscale/fscale.htm

[weatherwiz]

One thing to keep in mind is the Fujita scale was revised to more accurately incorporate changes within building codes and how foundations are built. With increased codes and stronger structures it's obviously a bit more difficult for buildings to get completely wiped out.

A couple other things to note is the wind speeds for the scale are only an estimation, winds can really get only so strong within a tornado...once you get to 300 mph that's really pushing it. I also believe those 318 mph winds in the Moore, OK area were measured by Doppler radar and the actual winds may have been a bit less...still incredibly impressive though.

Once you're getting into the EF5 category with regards to damage it's extremely difficult to rate it anything more b/c that alone is virtually total destruction.

[thewxmann]

Yes, there is such thing as an F6.

No, you'll never see a tornado rated as such.

The original Fujita Scale simply connected the Beaufort Scale to the Mach number scale. The F scale went from F0 to F12, with the lower bound of F12 set at Mach 1 (i.e. speed of sound), and the lower bound of F1 set at Beaufort Force 12 (73 mph). (Anything lower than Beaufort Force 12 was 'F0'.) You can't measure wind speeds in a tornado, so you try to assess the damage and correlate the damage you see with the windspeeds set by the Fujita Scale. These were complete estimates. But when they tried to correlate damage patterns to these windspeed estimates, they realized that one could not tell F5-windspeed damage from F6 or above-windspeed damage. You can't do worse than F5-windspeed damage - structures wiped clean from their foundations. So everything from F6 and above was discarded in practice.

Of course this has all been changed with the EF scale. There is now no upper bound on EF5, so there is no such thing as an EF6. And the EF scale is now an independent scale based on rigorous engineering studies conducted on how windspeed and damage correlate.

To address the other parts of your question--

The upper bound of F5 does hit 318 mph, but the fact that DOW measured that is really just a coincidence. And since the F scale uses damage to 'measure' windspeed, DOW could've measured 333 mph and F6 would not have been considered. (In fact, the damage was deemed to be a marginal F5, barely into the category.) The F/EF scales are damage scales - direct windspeed measurements are not taken into account when rating tornadoes. And as I said, you can't get worse than EF5 damage, so they will not add another EF level above EF5.

That aside, it is pertinent to note that the 318 mph gust was not measured at the surface, and so wouldn't be the culprit behind the surface-level damage seen during the Moore F5.

[iowahawkeyedave]

Ahh alright. Thanks everyone for the answers.

[Itunis]

Yes, there is such thing as an F6.

No, you'll never see a tornado rated as such.

The original Fujita Scale simply connected the Beaufort Scale to the Mach number scale. The F scale went from F0 to F12, with the lower bound of F12 set at Mach 1 (i.e. speed of sound), and the lower bound of F1 set at Beaufort Force 12 (73 mph). (Anything lower than Beaufort Force 12 was 'F0'.) You can't measure wind speeds in a tornado, so you try to assess the damage and correlate the damage you see with the windspeeds set by the Fujita Scale. These were complete estimates. But when they tried to correlate damage patterns to these windspeed estimates, they realized that one could not tell F5-windspeed damage from F6 or above-windspeed damage. You can't do worse than F5-windspeed damage - structures wiped clean from their foundations. So everything from F6 and above was discarded in practice.

Of course this has all been changed with the EF scale. There is now no upper bound on EF5, so there is no such thing as an EF6. And the EF scale is now an independent scale based on rigorous engineering studies conducted on how windspeed and damage correlate.

To address the other parts of your question--

The upper bound of F5 does hit 318 mph, but the fact that DOW measured that is really just a coincidence. And since the F scale uses damage to 'measure' windspeed, DOW could've measured 333 mph and F6 would not have been considered. (In fact, the damage was deemed to be a marginal F5, barely into the category.) The F/EF scales are damage scales - direct windspeed measurements are not taken into account when rating tornadoes. And as I said, you can't get worse than EF5 damage, so they will not add another EF level above EF5.

That aside, it is pertinent to note that the 318 mph gust was not measured at the surface, and so wouldn't be the culprit behind the surface-level damage seen during the Moore F5.

Interesting, I had no idea that was where the "F" designation came from. I would argue that you could get worse than F5 damage-complete destruction of a modern skyscraper. I remember some discussion about tornadoes and skyscrapers a few months ago, and the consensus was that they would withstand an F5, at least in terms of the structure itself. Couldn't say the same for the people and loose objects inside...

Of course we're just throwing around fantastical scenarios at this point. With how few F5s occur across the country there is a minuscule chance of one tearing through a downtown, much less a tornado stronger than any ever recorded...

[CapeFearWX]

Interesting, I had no idea that was where the "F" designation came from. I would argue that you could get worse than F5 damage-complete destruction of a modern skyscraper. I remember some discussion about tornadoes and skyscrapers a few months ago, and the consensus was that they would withstand an F5, at least in terms of the structure itself. Couldn't say the same for the people and loose objects inside...

Of course we're just throwing around fantastical scenarios at this point. With how few F5s occur across the country there is a minuscule chance of one tearing through a downtown, much less a tornado stronger than any ever recorded...

Heh, that would be like the zomgtornadoez that destroyed L.A. in The Day After Tomorrow :-P

[Amped]

Yes

F6- A tornado that kills you twice. So far none have been recorded.

[hm8]

Only in Smartmodel land.

[Witness Protection Program]

EFubar

[CapeFearWX]

Hey, if the Fujita scale doesn't go high enough for you, then how about the TORRO scale? It goes to 11!

http://en.wikipedia.org/wiki/TORRO_scale

It's like Nigel Tufnel designed it.

[battlebrick]

Didn't Fujita himself say the Xenia, OH F5 was the closest to an F6 he's ever seen?

[on_wx]

It would be pretty funny if back when they started using the Fujita scale they actually rated a tornado or two as F6 without knowing any better

[A-L-E-X]

One thing to keep in mind is the Fujita scale was revised to more accurately incorporate changes within building codes and how foundations are built. With increased codes and stronger structures it's obviously a bit more difficult for buildings to get completely wiped out.

A couple other things to note is the wind speeds for the scale are only an estimation, winds can really get only so strong within a tornado...once you get to 300 mph that's really pushing it. I also believe those 318 mph winds in the Moore, OK area were measured by Doppler radar and the actual winds may have been a bit less...still incredibly impressive though.

Once you're getting into the EF5 category with regards to damage it's extremely difficult to rate it anything more b/c that alone is virtually total destruction.

Paul, what I was led to believe was that the reason they went from the F-scale to the EF-scale was that the original scale overestimated the wind speeds needed to cause a given amount of damage. IOW, the scale isn't a measured wind scale like the Saffir Simpson scale, it's a damage scale. That's why I really think they should never have changed the name of the scale and kept it as the F scale and just adjusted the wind speeds downward. An F-5 from yesteryear is the same as an EF-5 today..... it's just that the wind speeds needed for Mag 5 damage have been adjusted downward. No one has ever actually been able to measure wind speeds this high, so they go by indirect evidence like the amount of damage caused..... and it is this that got adjusted and why the wind speeds for causing a given amount of damage on the "new" scale are different. It would have been so much less confusing if they had just kept the original name and simply changed the threshold for each level of the scale.

[OSUmetstud]

F6 is an inconceivable tornado in Fujita's original scale. No tornado has been rated that, though. It would be almost impossible to distinguish F5 damage from F6 damage, anyway.

[A-L-E-X]

F6 is an inconceivable tornado in Fujita's original scale. No tornado has been rated that, though. It would be almost impossible to distinguish F5 damage from F6 damage, anyway.

I have a question about the Joplin tornado-- I heard they rated it as a high EF4 with winds of 198 mph.... my question is how can they achieve the kind of accuracy needed to differentiate between a 198 mph wind and a 200 mph wind (which would have been an EF-5)..... and is there really even a visible difference at all between a 2 mph wind speed? It's a rhetorical question in a way, because I know there's no difference lol.... which is why splitting hairs between high EF-4 and EF-5 is pretty silly.... there is no conceivable way to tell apart the amount of damage caused by a 198 mph wind vs 200 mph wind. I've said the same thing with regards to a 155 mph Cat 4 vs a Cat 5 lol.

[CapeFearWX]

I have a question about the Joplin tornado-- I heard they rated it as a high EF4 with winds of 198 mph.... my question is how can they achieve the kind of accuracy needed to differentiate between a 198 mph wind and a 200 mph wind (which would have been an EF-5)..... and is there really even a visible difference at all between a 2 mph wind speed? It's a rhetorical question in a way, because I know there's no difference lol.... which is why splitting hairs between high EF-4 and EF-5 is pretty silly.... there is no conceivable way to tell apart the amount of damage caused by a 198 mph wind vs 200 mph wind. I've said the same thing with regards to a 155 mph Cat 4 vs a Cat 5 lol.

My best guess is that they settled on the strongest degree of damage found, which corrolated with high-end EF-4, and that according to the EF scale corresponds to a wind speed range of 190-198 mph. I don't know how many people are saying that the Joplin damage took EXACTLY 198 mph winds, but it's certainly a nice number for the media to quote.

I'm not sure how much credence the people doing the survey put into estimated wind speeds, but they do seem to do a MUCH more thorough job than they used to trying to determine how well-built the destroyed structures were and how much damage was done to them.

[Fred Gossage]

My best guess is that they settled on the strongest degree of damage found, which corrolated with high-end EF-4, and that according to the EF scale corresponds to a wind speed range of 190-198 mph. I don't know how many people are saying that the Joplin damage took EXACTLY 198 mph winds, but it's certainly a nice number for the media to quote.

I'm not sure how much credence the people doing the survey put into estimated wind speeds, but they do seem to do a MUCH more thorough job than they used to trying to determine how well-built the destroyed structures were and how much damage was done to them.

As we discussed yesterday in other threads associated with the Joplin tornado, that preliminary rating was a hold-me-over to let us know they would be giving it a very violent rating... but were still in the midst of doing detailed surveys. It seemed like, given that they did a telephone conference with media over an hour before releasing anything via NWS products... that they were trying to get info out for newscast time yesterday. It even seemed like they were hinting that they were strongly considering an EF5 rating by giving the 198 mph wind speed estimate and mentioning up to 200 mph winds in the write-up more than once. Now... after more detailed analysis done today... they have upgraded the tornado to an EF5.