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Enhanced Fujita Ratings Debate Thread

Equus

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Saw some more of that minimum possible on display after 3/17 with Moundville, Chilton, and the long track MS one pegged as high as possible without going to the next category; not sure what the aversion to upgrades is but it's certainly a much more conservative application than we had several years ago
 
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Scouring and debarking/denuding are (at least partially) functions of debris loading. Outside of crop fields and such, you'll notice that most severe vegetation damage tends to occur in proximity to or downstream from significant debris sources. It wouldn't necessarily be surprising to see a strong or violent tornado in an open area not produce the kind of high-end vegetation damage we might otherwise expect. You'd normally see uprooted (and occasionally lofted) trees at least, but even that isn't 100% guaranteed.

Vehicle damage is kinda weird, too. For instance, this study found that significant lofting/rolling of vehicles should be common at EF4+ intensity, yet field observations show only about 15% of vehicles in the paths of such tornadoes are actually flipped or thrown. In fact, around 36% of vehicles didn't move at all. Conversely, even EF1-EF2 tornadoes can very occasionally (~4% of the time) roll or loft vehicles.

In both cases, there are probably a ton of factors at work. The structure of a tornado is incredibly complex and ever-changing, so things like vertical velocity, gust factor, pressure forces, etc. can vary enormously even over incredibly short distances and timespans.

Also, re: winds in violent tornadoes being underestimated, there are a bunch of papers out there on different approaches to simulating tornadoes. It's a fascinating subject, and several of the simulations have exceeded anything we've actually observed. For instance, depending on the swirl ratio, some of the tornadoes in this simulation produced absolutely insane velocities. In one instance, both horizontal and vertical max gusts exceeded 400 mph.

Of course, it's important to remember these are idealized simulations and they don't take into account debris loading and other important factors. They almost certainly don't reflect anything you'd actually see in reality. Still, I think it lends some credence to the idea that we may be underestimating the maximum intensity of the most violent tornadoes.
I highly agree with you.
 
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Here's another one for you guys. This was probably one of the strongest January tornadoes ever recorded, striking and ripping a slash of death directly through the city of Warren, Arkansas on January 3, 1949, killing 55 people. Eyewitnesses described a multiple-vortex structure as the town was leveled. The tornado had a very long track that was documented from the air.

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This is really violent tornado damage of at least high-end F4 damage. It is even possible this tornado did F5 damage or reached that intensity. I like the way you guys are mentioning all the variables that may cause violent tornado damage. Like I have said before I have wondered what the velocities were on the Sherman, Texas tornado of 1896. It was quite narrow and produced some of the most extraordinary damage ever documented.
 
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This is really violent tornado damage of at least high-end F4 damage. It is even possible this tornado did F5 damage or reached that intensity. I like the way you guys are mentioning all the variables that may cause violent tornado damage. Like I have said before I have wondered what the velocities were on the Sherman, Texas tornado of 1896. It was quite narrow and produced some of the most extraordinary damage ever documented.
Sherman reminds me a bit of Pampa, TX of 1995; a "drillbit" type, real narrow but EXTREMELY intense damage. The thing about these tornadoes is that they pretty much have to hit something dead on to do any damage but when they do it's more or less total annihilation.
 
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Sherman reminds me a bit of Pampa, TX of 1995; a "drillbit" type, real narrow but EXTREMELY intense damage. The thing about these tornadoes is that they pretty much have to hit something dead on to do any damage but when they do it's more or less total annihilation.
I usually watch a bunch of EAS scenarios of tornadoes on YouTube and of course they are hypothetical. It is usually like what if a 3 mile-wide EF5 tornado with winds around 350 mph hit say a city like Chicago dead on? I tend to also ask what if you had a small drill bit EF5 tornado (50-100 yards wide)with inner winds of 375 mph and outer winds of 325 mph hit a major metropolitan dead on? Of course I think the much larger tornado would cause more damage and casualties but of course the small drill bit would still not be any less pleasant than even the huge wedge tornado.
 
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I usually watch a bunch of EAS scenarios of tornadoes on YouTube and of course they are hypothetical. It is usually like what if a 3 mile-wide EF5 tornado with winds around 350 mph hit say a city like Chicago dead on? I tend to also ask what if you had a small drill bit EF5 tornado (50-100 yards wide)with inner winds of 375 mph and outer winds of 325 mph hit a major metropolitan dead on? Of course I think the much larger tornado would cause more damage and casualties but of course the small drill bit would still not be any less pleasant than ever the huge wedge tornado.
Well with a wedge the narrow suction vortices and core would do most of the damage, not the main outer circulation. So damage would probably be wildly selective but overall perhaps a bit more (financially at least). In terms of death toll it would depend if it went through the downtown area, suburbs, followed a freeway corridor, etc. So many variables to think about.
 
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Well with a wedge the narrow suction vortices and core would do most of the damage, not the main outer circulation. So damage would probably be wildly selective but overall perhaps a bit more (financially at least). In terms of death toll it would depend if it went through the downtown area, suburbs, followed a freeway corridor, etc. So many variables to think about.
I agree. To think what 2 tornadoes like the ones I described hitting a major metropolitan area dead on. Both of them being long lived and long tracked. The debris ball signature and radar presentation would be absolutely terrifying.
 
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I agree. To think what 2 tornadoes like the ones I described hitting a major metropolitan area dead on. Both of them being long lived and long tracked. The debris ball signature and radar presentation would be absolutely terrifying.
I wonder what the Tri-State tornado's debris ball and radar signature would have looked like. It'd probably be unprecedented (at least the debris ball would be).
 

Tennie

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So recently this study was published regarding tornado wind speeds (it's open access, thankfully):


Basically, the Doppler on Wheels (DOW) vehicles measured fairly low-level wind speeds inside a number of tornadoes over the years, and the measured speeds (and corresponding EF-scale ratings) were compared to official NWS damage ratings of the same tornadoes. What was found was that the damage ratings seem to be about 1-2 categories lower (on average) than the radar-measured winds would indicate, suggesting that it usually requires stronger winds to cause at least particular degrees of damage than was previously believed. This and (perhaps) other future studies should at the very least be given some consideration in the future regarding damage ratings.
 
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my problem with using vegetation of any kind as contextual damage that affects a tornadoes rating. especially with a building near by. is the fact that vegetation behaves wildly different in strong winds than buildings do. buildings like frame homes are sturdy little to no give what so ever. they resist winds almost 1 hundred percent till a critical point of failure is reached. then the house will immediately begin being destroyed in a quick process as all that pressure is released and the house is taken apart.

vegetation just doesn't have these properties apart from really mature hardwood trees. (which tend to snap or lose all there branches compared to softwood trees which lose maybe a few branches and then the bark. but that's about it until the winds get extreme.) trees and grass have alot of give compared to buildings. and are much more resistant to being harmed. this is why for softwood trees and low lying shrubbery, you'll often see most of the branch structure intact with only surface damage. and grass also. since its so low to the ground it doesn't get affected as much by winds. so unless in very violent scenarios using vegetation just isnt very accurate as contextual damage.

A medium sized wood from structure that is well bolted to its foundation got swept away by a powerful tornado.
however. there are trees a few yards away from the foundation. you notice they are softwood trees with a deep root structure, and smooth bark.
all that's noted for damage is most of the top branches are removed and some minor debarking has occurred. the grass in the area is also mostly unscaved.

would you rate this tornado an ef3, or an ef5?
the house is swept away. debris is lightly granulated. and an anchore bolt is bent. high end ef4 to ef5 damage for sure.

but then again the vegetation damage is more in tune with ef3 winds.

traditional ratings would put this house at either a high end ef3 or low end ef4.
but remember what i told you earlier?
this is just to much of a difference and what i mentioned explains that inconsistency.

i would personally offer the solution of splitting the damages rated into four major groups.
(structures, vegetation, heavy objects, and embedded objects) and come to an average rating after rating a strong to violent tornado based on each group of indicators individually.

then again im not a professional. so let me know what you think.
 
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i also personally find the under-rating of vilonia to be quite offensive.

large frame house is completely swept away. minor scouring of grass. most trees in the area snapped or partially debarked. car mangled nearby. but eh all because that house's bolts were bent but didn't have any nuts or washers. lets just drop the entire area down to an ef3 rating and ignore a bunch of other stuff. "shouldn't cause any issues right?"

they just dont seem to understand that nit picking will cause a large number of problems.

debris impacted the structure
the house had pre-cracked bolts
this tree has a leaf left on it
that car is still in place
the grass here is fine

ive seen them all and im sick of them. they cause way to much trouble
 

Equus

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Regarding rating consistency, this is one reason it's so incensing to hear claims that modern EF ratings should be treated 1:1 like historical F scale ratings
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The Belmond tornado is on official record still as an F5 for smearing a very small poorly anchored house into large, generally not shredded debris; either a section of roof or floor is clearly still intact back there. This remains an F5 while modern tornadoes that slab thousands of better built homes remain EF4 because construction is only average not superior.

(For what it's worth Grazulis lists Belmond as F4 which seems fair since many other homes were also destroyed and Belmond itself was devastated, just apparently to only minimal F4 level; F5 rating is apparently based on that house)
 
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Regarding rating consistency, this is one reason it's so incensing to hear claims that modern EF ratings should be treated 1:1 like historical F scale ratings
View attachment 11009
The Belmond tornado is on official record still as an F5 for smearing a very small poorly anchored house into large, generally not shredded debris; either a section of roof or floor is clearly still intact back there. This remains an F5 while modern tornadoes that slab thousands of better built homes remain EF4 because construction is only average not superior.

(For what it's worth Grazulis lists Belmond as F4 which seems fair since many other homes were also destroyed and Belmond itself was devastated, just apparently to only minimal F4 level; F5 rating is apparently based on that house)
Belmond being rated F5 is ridiculous. I'd even say it doesn't look as violent as some top-tier EF3 tornadoes in the 21st century (e.g. Sulphur, OK 2016).
 
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locomusic01

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Belmond being rated F5 is ridiculous. I'd even say it doesn't look as violent as some top-tier EF3 tornadoes in the 21st century (e.g. Sulphur, OK 2016).
Yeah, I haven't done a ton of research on it, but I don't think I've seen or read anything that leads me to believe Belmond would be anything more than high-end EF3 or low-end EF4 were it to happen today. There was a lot of damage throughout town, but very little of it looked particularly violent.

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It did throw around some train cars outside of town in an area where trees were reportedly stripped bare and there may have been some scouring, but unless there was some high-end damage somewhere that I haven't seen (which is possible), it doesn't exactly scream "violent tornado."

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I know the Belmond Historical Society has lots of pictures that aren't available elsewhere; at some point maybe I'll contact them and see if they're digitized. IIRC they also have a book w/photos and news clippings and such.
 
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if the western kentucky tornado remains rated EF-4 and not get the upgrade it deserves the nws officially loses all respect from me. i will never ever listen to a rating they give out ever again.
 
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I just don't know what they're looking at to say this was a high end EF4
its a preliminary rating....but people are saying it could remain that way. and if it does....we'll probably pester them into upgrading it to an EF-5. we all know it was an EF-5 with strength to rival smithville 2011. their rating is irrelevent if they keep it as an EF-4. cause its just objectively false. idc what they say at this point. the EF-scale is broken and they're crap at their jobs.
 
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