Enhanced Fujita Ratings Debate Thread (3 Viewers)


pohnpei

Member
Messages
5
Location
shanghai
Today NWS Nashville has just released pictures of all 26 EF4 rating postion of cookeville tornado, actully most of these EF4 damage houses were well constructed residence, some being metioned had J bolt and some was attached to the foundation very well. Most of them swept clean as we all can see easily. For dayton tornado last year on 5/27 earned 170mph without EF4 structure damage and this one get 175mph with tons of well constructed FR12 residence swept clean, the inconsistency among different NWS was just such great.
034718pz3g36jmdcamwwau.jpg035412fcuxq8hnc9hx3hul.jpg034053s1m19qmknjmuy9nz.jpg033936dfxz7xo7a3xoznnt.jpg
 

Equus

Member
Messages
1,506
Location
Saragossa, AL
I've gotten to the weird point where I'm so relieved to see a WFO rate obvious violent damage as violent (more often than not, mid EF3 is absolute tops) that I won't even argue too hard for an even higher rating up the violent scale. Given the anchor bolts present in some of the pics, and the death ratio, Cookeville was obviously more violent than a decent chunk of F5 rated tornadoes on the historical record, but as we all know, the more stringent criteria of the last 18 years or so has rendered historical comparisons moot. It is more violent than many official EF4s but I don't see too much that would confidently push it higher.

The main factor limiting EF5 according to some discussions I've seen is the probability that chunks of less well constructed homes were thrown at the bolted ones, compromising their integrity; while this is very likely, it still seems nit-picky, and seems to be a way of saying "no home damage will ever be rated EF5 again unless it's completely isolated from any other structure or debris source AND well above official state construction code" which seems exceptionally arbitrary and nigh impossible. Slabbed well constructed homes has always been an F/EF5 hallmark and there's no reason to hold that to excessive conditions - it's just a six point scale used to file events away, not something that should be overly complicated.

I WILL say, that while the structural damage at Cookeville is significantly worse than at Beauregard imo (and is vastly worse than Dayton) and tree damage screams violent, contextual factors don't impress me as much as our more recent EF5s and even some high EF4s; Vilonia having worse scouring and debarking and even cleaner slabs/higher death toll, and Chapman/Beauregard had far higher end vehicle damage. If those tornadoes weren't rated EF5 (though Vilonia objectively should have been) then the contextual factors would seem to limit this to mid EF4. Given those contextual factors, I'm fine with the rating despite severe slabbing.

And as bad as Cookeville was... incredibly, it was almost significantly worse. Thank exceptionally rapid dissipation.

baxtercookevilletormap~2.jpg
 

buckeye05

Member
Messages
250
Location
Riverside, Ohio
Equus said it perfectly. The number of slabbed, anchored homes does raise an eyebrow, but contextual evidence for EF5 is glaringly missing. There was no extreme debarking, scouring, or vehicle damage in this tornado. While some of these things are present, its not what you’d see in an EF5. Also, the debris patterns weren’t overly impressive (EF5 typically has a finely granulated “explosive” look to it). Overall, I’d say EF4 is very much appropriate, and I can say with a high degree of confidence that this wasn’t an EF5. Keep in mind that EF5 is for the absolute most violent, extreme damage possible. The Cookeville damage doesn’t quite fit that category. Also keep in mind that there is clear evidence of debris cleanup in these pics.

Only thing is I would have gone with a slightly higher wind speed estimate if it were up to me.
 

buckeye05

Member
Messages
250
Location
Riverside, Ohio
Here's something that I see in damage surveys that always irks me. It's become clear to me that certain WFO survey teams do not have a good grasp on the varying degrees of tree damage. The Cantril, IA EF3 tornado from 05/27/2019 is a perfect example. Surveyors called this EF3 tree damage, which is defined as severe debarking with only stubs of largest branches remaining. This tree is not debarked or denuded. Not even a little bit, but they went with EF3. Then on the other end of the spectrum, sometimes you will see severe actual debarking rated EF2. I hate to question professionals, but when I see stuff like this, I have to ask "Do you guys really know what you're doing here?" Is it possible that some surveyors aren't clear on what actual debarking looks like? I really can't help but think that might be the case sometimes.
 

Lori

Administrator
Staff member
Administrator
Moderator
Messages
844
Location
Pelham, AL
Special Affiliations
SKYWARN® Volunteer
The Cookeville, TN damage looked a lot like Tuscaloosa, AL EF-4 on April 27, 2011 IMO
 

Users Who Are Viewing This Thread (Users: 0, Guests: 1)

Top