Highest theoretical windspeed in a tornado?

[scott r currens]

The theory behind f-6 level damage is that even if it were to occur, you would not be able to recognize it among the total destruction that happens with f-5 level [or ef-5 level...whatever.]

There are structures that have taken direct hits from F-5 tornadoes without being damaged. Steel-reinforced concrete structures like over-passes rarely suffer any damage from tornadoes even violent ones. I'm not going to argue for rating tornadoes (E)F-6 but I think it would be possible to come up with damage indicators above what we have for (E)F-5.

 

[Rob Wadsworth]

I'd chase an F12....!!

LOL!
I'll split the difference with you, and say I would even chase an EF-9


Mind-blowing to consider such a wind force

 

[Shane Adams]

I don't recall seeing all the damage indicator levels in the F-scale, nor did I see much real research into actual wind speeds (at least to the level that was incorporated to the EF scale.)

The F-Scale was more theoretical wind speeds. The EF-scale is much closer to reality.

I'm just keeping it simple, the way the general public would perceive it....

Roof damage was F1 in 1985. It still is.

Leveled brick homes littered with debris was F4 in 1985. Still is.

Clean-swept slabs were F5 in 1985. They still are.

My point is, outside of the weather community, it's the same scale but with a different name. When laymens ask why the name change, the subject of windspeeds comes up...and that they were changed. This just confuses an already-confused person who only knew the F-scale from "Twister".

I get the science behind it, so we don't need to play the technical game about this. The point is, the general public would've never known anything changed if the name had stayed the same...because the general public doesn't understand the science behind it. It just seems pointless to change the name based on windspeed theories, when science has preached to us for 30 years that it's a damage scale.

I'm perfectly fine that the weather world calls it the EF scale. But I'll just stick with F.

 

[Greg Stumpf]

It just seems pointless to change the name based on windspeed theories...

The name wasn't really changed. The F-Scale was "enhanced" by:

1) Re-estimating the wind speeds associated with damage to single-family residences.
2) Adding more damage indicators beyond single-family residences.
3) Making the scale flexible to accept new DIs, and to accept changes to the wind speed estimates as the science improves.

The essence of the original Fujita Scale is still there.

 

[Greg Stumpf]

I'll also add that if a tornado rating was based on single-family residences, then yes, F = EF across all categories, and nothing is really changed except the wind speed estimates associated with those degrees of damage. An F5 house 10 years ago is an EF5 house today, and so on.

But, if information about damage to other DIs that are now incorporated in the enhanced F-Scale is included on a historic survey, there is the possibility that EF > F for the same tornado.

 

[Jeff Duda]

I've been at the SLS conference in Denver this week and Rich Thompson showed a poster and Roger Edwards gave a talk about the EF-scale and possible updates to it. Perhaps some significant changes will eventually emerge.

Relating to the original topic of the thread, I would think one could do a scale analysis of a simplified vorticity equation or some other balanced wind equation (cyclostrophic flow) on the tornado scale to estimate the maximum winds that could occur. It would help, of course, to have measurements of other extremes that come with tornadoes, such as pressure perturbations at the core and the like.

 

[Kyle C Williams]

Good idea Jeff, im sure that you could estimate whatever the maximum of all the paremeters could potentially be and then come up with an estimate.

 

[Jason Foster]

I still like using F-scale personally (and you'll see that in any video of mine). EF-scale just seemed "pussified" to me. Sorry...it just does.

LOL. Howard...yes, it certainly would.

Rob...sure thing.

The only thing I won't chase is an F13 (aka: a blackhole) because you can't upload the video back to the networks...

 

[cnichols]

Theoretically ... I guess speeds are limited by subsonic compressible fluid flow formulas

 

[Robert Edmonds]

Like the question. Can't answer it but we could look at it in a different light. Just played around and came up with...

So what this is saying is that the velocity of the parcel will be equal to the root of the pressure drop divided by the density of the parcel. Would be glad to explain more about the 'massaging' of the equations. In the end largest change in pressure I could reason, leads me to wind speeds in the low 300 mph. However, I guess another way to ask the question for this thread, what is the lowest change in pressure one could imagine for a tornado?

 

[Jeff Duda]

Like the question. Can't answer it but we could look at it in a different light. Just played around and came up with...

So what this is saying is that the velocity of the parcel will be equal to the root of the pressure drop divided by the density of the parcel. Would be glad to explain more about the 'massaging' of the equations. In the end largest change in pressure I could reason, leads me to wind speeds in the low 300 mph. However, I guess another way to ask the question for this thread, what is the lowest change in pressure one could imagine for a tornado?

Glad someone got around to playing with this. I figured one would need info on the pressure field to obtain max wind speeds. However, I would have to disagree with the assumption of a linear pressure change. I bet it's more likely to be logarithmic or exponential in nature (at least according to pressure traces I've seen of tornado near-core pressure data).

 

[Robert Edmonds]

Glad someone got around to playing with this. I figured one would need info on the pressure field to obtain max wind speeds. However, I would have to disagree with the assumption of a linear pressure change. I bet it's more likely to be logarithmic or exponential in nature (at least according to pressure traces I've seen of tornado near-core pressure data).

If you use a rankine vortex patch you get the same answer. That has pressure increasing r^2 from the center and r^-2 after v_max.

Believe I got the Lamb-Osceen vortex too, you get the same equation except times an additional 0.76 (could have made a mistake some where though).