Enhanced Fujita Ratings Debate Thread

[slenker]

The general assumption I've seen is that the speeds are additive, which is used in, amongst other things, the interpretation of doppler radar data. This is the opposite of what you're assuming.

I’m sorry if I’m missing something, but I’m still confused here. The subtraction I’m using follows the same principle as using addition. Depending on which reference frame I’m looking at, the operations switch. From the frame of the stationary anemometer, the windspeed it measures is 153 mph. The tornadic wind it measured would have to take into account both the translational speed of the tornado and the windspeed with respect to the tornado itself, so that 153 mph could be broken up into two components. This is because the tornado itself is moving in this frame, along with the winds.

If I’m looking at the reference frame of the tornado itself, then the tornado is now moving at 0 mph because it is at rest in this frame. So, the only “windspeed” from this frame would be only one of the components, and it wouldn’t be the translational speed. That’s the “windspeed” I was talking about in my posts above.

But, now that I think about it, it doesn’t matter what the windspeed from the tornado’s frame is - all that really matters is what a stationary frame would experience, because that is what a home or trees would feel in the event of a tornado. So my original point is practically moot anyways.

 

[joshoctober16]

I do believe this is that Mesonet station afterwards. I got this photo from a friend who knows a mesonet tech

any idea what direction this is faceing? , the tornadoes core would be to the north and we should be able to likely see far away contextual EF3 damage.

interesting to note that despite a 150 mph with debris hitting it , it isn't looking damaged at all , fence is standing quite fine as well.

 

[NewFoundWeatherNerd]

any idea what direction this is faceing? , the tornadoes core would be to the north and we should be able to likely see far away contextual EF3 damage.

interesting to note that despite a 150 mph with debris hitting it , it isn't looking damaged at all , fence is standing quite fine as well.

Im not sure, but I can ask later today and find out for yall

 

[US_Highway15]

The Essex tornado being rated an EF1 in my opinion is the textbook example of everything wrong with the Enhanced Fujita scale. The margin of a tornado being rated an EF1 and an EF3+ should not be determined by a twister missing a town by a mile. If the tornado was capable of producing EF3+ damage, then it should be rated as such. We rate hurricanes based off wind speeds. I don't see the problem with doing the same thing for tornadoes. With the way technology is today, I would like to think its never been easier to determine a tornadoes strength/wind speed without having to rely on houses being destroyed to measure.

 

[slenker]

Rating tornadoes based off of measured wind speed is not a good idea in my opinion, at least with the technology we have now. If that were the case, then tornadoes that are clearly not capable of inflicting EF5 damage would be rated EF5. Extreme windspeed measurements are typically not taken near ground level, they’re normally higher than 50 meters. The only example I can think of off the top of my head where an extreme windspeed was actually taken in the “damage layer” was El Reno 2011, which IIRC had its 295 mph gusts taken 20 meters AGL. Greenfield was also kind of closer to the ground, I think it was ~46 meters AGL for the 309+ mph measurement. Don’t get me wrong, I do think that tornadoes should be rated based on the maximum damage they can potentially inflict on the ground eventually. But windspeed is far too inconsistent of a measurement to do this, so damage remains the best way to rate a tornado. Greenfield’s extreme wind measurements were taken in conjunction with damage from a ~165 mph EF3.

Some examples that make this not a good idea IMO:

1. One of the Dodge City 2016 tornadoes: DOW measured windspeeds of 200+ mph when it was constructing and dying. This tornado was most certainly not capable of inflicting such damage, and there aren’t any damage photos to ground or trees supporting this idea.
2. Harlan 2024: The wind gust that was measured at 224 mph occurred ~600 m AGL and coincided with the tornado not being fully condensed - I know this second point isn’t necessarily the greatest argument against it, but after watching video of Harlan and comparing it to genuine EF5s, it becomes clear that Harlan wasn’t anywhere close to such an intensity despite the reading.
3. Andover 2022: Not DOW windspeeds per se, but photogrammetry revealed that the Andover 2022 tornado had wind gusts exceeding 250 mph in the core of the vortex under 50 m AGL. This is technically enough to grant it an IF5 rating based on the international Fujita scale. But it was most certainly not capable of inflicting EF5 damage at any point in its life - it went through a populated area and did some very impressive EF3 damage, borderline EF4, but to call that one an EF5 is not representative of the intensity it takes to reach that level.
4. Hollister 2024: Insane radar presentation, over 200 mph of GTG shear measured across multiple scans, clearly a big wedge, but did very unimpressive tree damage whilst moving very slowly. This one belongs in the hall of fame of tornadoes that appeared monstrous on radar but actually did very little outside of that - I’m pretty sure it’s believed the insane radar presentation was because the winds aloft were extreme but never fully translated to the ground, for strange reasons that I am not familiar with.

In my opinion, I believe the point about tornadoes having higher windspeeds than the EF scale reasonably estimates better supports the argument that the EF scale is consistently underrating the strength of winds in general. Wind measurements are simply not good enough as they stand currently, especially when the winds are taken from radar measurements that are not DOW. That’s my two cents.

EDIT: Also, I’m not saying that Greenfield wasn’t capable of EF5 damage, it clearly was at some point - my points are more towards the other tornadoes I mentioned above.

 

[Aaron Rider]

The Essex tornado being rated an EF1 in my opinion is the textbook example of everything wrong with the Enhanced Fujita scale. The margin of a tornado being rated an EF1 and an EF3+ should not be determined by a twister missing a town by a mile. If the tornado was capable of producing EF3+ damage, then it should be rated as such. We rate hurricanes based off wind speeds. I don't see the problem with doing the same thing for tornadoes. With the way technology is today, I would like to think its never been easier to determine a tornadoes strength/wind speed without having to rely on houses being destroyed to measure.

Do we have any photos indicating potentially strong context with Essex? Trees, ground scouring, etc

 

[AJS]

Do we have any photos indicating potentially strong context with Essex? Trees, ground scouring, etc

As far as I know, nothing yet. The thing with the Essex tornado is that it genuinely looked like a monster based on the live captures of it. So I would not be surprised to see some potentially strong context.

 

[US_Highway15]

Do we have any photos indicating potentially strong context with Essex? Trees, ground scouring, etc

I have two photos from the NWS damage survey. The first picture was taking about half a mile to a mile (if even that) in the tornadoes path, and the second one was right in the middle of the tornadoes path, I would guest judging by the picture, when it was at it's strongest point. Both are outbuildings. Second one, I understand it's an outbuilding, but that seems the most damning. There is a third picture that includes houses, but its just barely any roof damage, and that was when the tornado had already taken a NE turn and was in the process of lifting/weakening.

 

[jiharris0220]

I have two photos from the NWS damage survey. The first picture was taking about half a mile to a mile (if even that) in the tornadoes path, and the second one was right in the middle of the tornadoes path, I would guest judging by the picture, when it was at it's strongest point. Both are outbuildings. Second one, I understand it's an outbuilding, but that seems the most damning. There is a third picture that includes houses, but it’s just barely any roof damage, and that was when the tornado had already taken a NE turn and was in the process of lifting/weakening.View attachment 39939View attachment 39940

This by all means looks like ef1 damage, the outbuilding is literally made out of sheet metal, the camper didn’t even get flipped over.

Large tornado≠strong tornado.

The pressure gradient of this thing was definitely broad for tornado standards, and the TVS is not representative for what’s happening at the surface.

Hollister last year is a good example that just because a tornado is large and the TVS is significant, doesn’t mean you’re going to see impressive damage.

This tornado was just a large and weak condensation funnel with no concentrated area of vorticity to generate strong mesovortices or a centralized, violent core inside its condensation funnel.

 

[Kds86z]

This by all means looks like ef1 damage, the outbuilding is literally made out of sheet metal, the camper didn’t even get flipped over.

Large tornado≠strong tornado.

The pressure gradient of this thing was definitely broad for tornado standards, and the TVS is not representative for what’s happening at the surface.

Hollister last year is a good example that just because a tornado is large and the TVS is significant, doesn’t mean you’re going to see impressive damage.

This tornado was just a large and weak condensation funnel with no concentrated area of vorticity to generate strong mesovortices or a centralized, violent core inside its condensation funnel.

Hmm, I guess it’s possible damage was on the outside of its core winds or it was roping out stage

 

[US_Highway15]

This by all means looks like ef1 damage, the outbuilding is literally made out of sheet metal, the camper didn’t even get flipped over.

Large tornado≠strong tornado.

The pressure gradient of this thing was definitely broad for tornado standards, and the TVS is not representative for what’s happening at the surface.

Hollister last year is a good example that just because a tornado is large and the TVS is significant, doesn’t mean you’re going to see impressive damage.

This tornado was just a large and weak condensation funnel with no concentrated area of vorticity to generate strong mesovortices or a centralized, violent core inside its condensation funnel.

Fair enough. Just odd that a 1.7 or 1.8 mile wide tornado only had a maximum of 110 MPH winds. That's weather I guess.

 

[Kds86z]

Fair enough. Just odd that a 1.7 or 1.8 mile wide tornado only had a maximum of 110 MPH winds. That's weather I guess.

Lots of wedge weak rated tornadoes.

 

[jiharris0220]

Fair enough. Just odd that a 1.7 or 1.8 mile wide tornado only had a maximum of 110 MPH winds. That's weather I guess.

Again though, size does not equal strength.

A large tornado means a flatter pressure gradient, which is what determines wind velocity, and most wedges are weak because of this fact, even with contextuals taken into account.

Large tornadoes over come this issue by either concentrating areas of high potential vorticity within their funnels to form meso vortices, or form a smaller central column of air inside of the main funnel; which produces a substantially tighter pressure gradient.

Wedges like smithville and bridge creek had a central violent core inside their condensation funnel, which is what produced the violent damage.

El Reno 2013 produced its borderline violent damage from meso vortices.

This tornado however based on contextual and conventional damage seemed to have nothing but it’s broad funnel, which is why the damage is so lack luster.

 

[Lake Martin EF4]

Screw it here's a list of tornadoes (that I know of) that would likely get EF5 if they happened today:

1925 Tri-State
1953 Flint
1956 Hudsonville
1957 Fargo (?)
1965 Coldwater Lake #1
1965 Sunnyside
1965 Pittsfield-Strongsville
1970 Lubbock
1974 Brandenburg
1974 Tanner #1
1974 Guin
1977 Smithfield
1985 Niles-Wheatland
1990 Hesston
1990 Goessel
1991 Andover
1992 Chandler (?)
1996 Oakfield (?)
1997 Jarrell
1998 Waynesboro (?)
1999 Bridge Creek
2004 Marion (?)
2007 Greensburg
2008 Parkersburg
2011 Philadelphia (?)
2011 Hackleburg
2011 Smithville
2011 Tuscaloosa (?)
2011 Rainsville (?)
2011 Ringgold
2011 Joplin
2011 Piedmont
2011 Chickasha
2011 Goldsby
2013 Moore
2014 Vilonia
2014 Louisville (?)

 

[AJS]

Screw it here's a list of tornadoes (that I know of) that would likely get EF5 if they happened today:

1925 Tri-State
1953 Flint
1956 Hudsonville
1957 Fargo (?)
1965 Coldwater Lake #1
1965 Sunnyside
1965 Pittsfield-Strongsville
1970 Lubbock
1974 Brandenburg
1974 Tanner #1
1974 Guin
1977 Smithfield
1985 Niles-Wheatland
1990 Hesston
1990 Goessel
1991 Andover
1992 Chandler (?)
1996 Oakfield (?)
1997 Jarrell
1998 Waynesboro (?)
1999 Bridge Creek
2004 Marion (?)
2007 Greensburg
2008 Parkersburg
2011 Philadelphia (?)
2011 Hackleburg
2011 Smithville
2011 Rainsville (?)
2011 Joplin
2011 Piedmont
2011 Chickasha
2011 Goldsby
2013 Moore
2014 Vilonia
2014 Louisville (?)

I honestly don’t believe Hackleburg would get an EF5 rating today. The construction quality throughout the path would’ve been over analyzed and nit picked to death.

 

[Lake Martin EF4]

I honestly don’t believe Hackleburg would get an EF5 rating today. The construction quality throughout the path would’ve been over analyzed and nit picked to death.

Don't forget, though - it would be the Huntsville and Birmingham offices surveying. Both are very liberal.

 

[AJS]

Don't forget, though - it would be the Huntsville and Birmingham offices surveying. Both are very liberal.

That is true. They do take contextual evidence into hand. Which is a good thing cause Hackleburg without a doubt caused some of the most extreme contextual damage ever seen.

 

[Lake Martin EF4]

That is true. They do take contextual evidence into hand. Which is a good thing cause Hackleburg without a doubt caused some of the most extreme contextual damage ever seen.

When making this, for quite a few cases I figured who would be surveying it into the equation. Example: Ringgold. I am fairly certain that would be EF5 because the NWS office surveying it (Peachtree City) is not only liberal but arguably *too* liberal, to the point that they sometimes OVERrate tornadoes (*COUGH*newnan*COUGH*). I do know there are possible EF5 candidates in GA from that one, and truth be told I'm fairly sure that Peachtree City would apply an EF5 to those spots even if they didn't strictly meet EF5 standards. Actually, I'd wager they might also give an EF5 to Barnesville too, but that's a lot more conditional and it's more likely they give it high end EF4 instead.

 

[AJS]

When making this, for quite a few cases I figured who would be surveying it into the equation. Example: Ringgold. I am fairly certain that would be EF5 because the NWS office surveying it (Peachtree City) is not only liberal but arguably *too* liberal, to the point that they sometimes OVERrate tornadoes (*COUGH*newnan*COUGH*). I do know there are possible EF5 candidates in GA from that one, and truth be told I'm fairly sure that Peachtree City would apply an EF5 to those spots even if they didn't strictly meet EF5 standards. Actually, I'd wager they might also give an EF5 to Barnesville too, but that's a lot more conditional and it's more likely they give it high end EF4 instead.

I actually don’t get why they rated Newman EF4. All of the images I have seen from Newman point to a tornado no higher than an average EF3 tornado.

 

[A Guy]

Again though, size does not equal strength.

A large tornado means a flatter pressure gradient, which is what determines wind velocity, and most wedges are weak because of this fact, even with contextuals taken into account.

Large tornadoes over come this issue by either concentrating areas of high potential vorticity within their funnels to form meso vortices, or form a smaller central column of air inside of the main funnel; which produces a substantially tighter pressure gradient.

Wedges like smithville and bridge creek had a central violent core inside their condensation funnel, which is what produced the violent damage.

El Reno 2013 produced its borderline violent damage from meso vortices.

This tornado however based on contextual and conventional damage seemed to have nothing but it’s broad funnel, which is why the damage is so lack luster.

Not really. There's a consistent observed relationship between tornado size and strength, which has come up in practically every paper I've read that cared to measure. This doesn't mean you can't have small violent or large weak tornadoes, but the tendency is the stronger, the wider.

The Edwards et al paper I mentioned in another thread about changes in surveyed tornado widths between the F and EF eras provides some good graphs (and a massive sample size, from 1995 to 2018 with 29336 tornadoes).

Average path width (in metres) by damage rating, blue F and red EF:



Probability functions, same colours, A=F/EF0, B=F/EF1, C=F/EF2 and D=F/EF3+:



Distribution functions, ditto:



Distribution of percentiles, with the yellow being 10th, 50th and 90th, and F scale percentiles on the horizontal and EF on the vertical:



You'll notice the 90th width percentile of a lower rating category lies not that far off the 50th of the next highest. And that an 1800 metre wide EF1 tornado lies outside the 99th percentile (the axis isn't even that long). So it's pretty unusual in fact.

Condensation funnel width has a somewhat loose relationship with the path width (at least according to Wakimoto), but most examples I've seen it's under half of the surveyed width.