Enhanced Fujita Ratings Debate Thread

[SweptSlab5]

My takes on these over the years:

1.) I call this vehicle disassembly. When the vehicle is either stripped down to its chassis or literally torn apart into multiple pieces. Usually only seen in very high-end EF4 or EF5 candidate events, or in suspected extremely violent tornadoes that didn’t hit much (Spiritwood, ND for example)

2.) If we’re talking about buckling or partial dislodging of thick reinforced house or business foundations, then yes absolutely a good indicator of extreme intensity, and incredibly rare. The restaurant in Mount Hope is a great example, and honestly the only definite one I can think of right now. But…this is not the case if we’re talking about a small surface concrete foundation for a shed, or outbuilding, or grain bin or something. Those are usually poured thin and without reinforcements, so they can crack and buckle surprisingly easy. I’ve seen a thin pole barn slab buckle in an EF2. So in a nutshell, yes but only if it’s a thick slab.

3.) Extreme debarking and tree damage can indeed be a high-end indicator, especially if it takes place in rural areas without much debris loading. Think Louisville, Bassfield, Buckeye, Enderlin, Chickasha, El Reno/Piedmont, Vilonia, rural parts of the Bridge Creek path, rural parts of the Moore 2013 path, and rural parts of the Hackleburg path. Extra significant if multiple trees are completely stubbed and have literally zero bark remaining; as in genuine 100% debarking. Even more so if the trees are both root balled and totally debarked (Harper 2004 and Philadelphia 2011).

4.) Shrub shredding and debarking is another good high-end EF4 to EF5 indicator, but it has to be genuinely severe, not just partial. A good indicator of extreme low level winds, and provides great contextual support if the shrubs are around the perimeter of a well-anchored slabbed home.

5.) Good high-end indicator, but one to three feet is not genuine granulation or mulching, as plenty of tornadoes do that. Genuine granulated debris is fine enough to literally pour out of the palm of your hand, can fill up a glass mason jar, and is literally coin/wood-chip sized (think Parkersburg). This is very rare, and therefore one of the more reliable high-end indicators. Debris granulation is one of the most misunderstood contextual indicators, because people frequently see regular scattered debris and call it granulation when it’s not actually granulated. It truly has to be finely ground up into teeny tiny little fragments to be considered real granulation.

6.) Some cycloidal/spiral markings can be considered an EF5 indicator if analyzed mathematically. This is admittedly not something I know very much about. Ask @Saltical Wx for more info on this.

7.) Hmmm….if it occurs in association with the destruction of a well-built, reinforced concrete building, then I’d say possibly. Problem with this, is it can also snap due to shifting weight and gravity as a building fails, but not necessarily wind. For example, rebar snapped within the walls of a collapsing factory building in Adairsville, GA back in 2013. That was an EF3 tornado, and the wind broadsided a massive factory wall, which fell, snapping the rebar, but not as a direct result of the wind, and not from a particularly violent tornado. I do however, recall a rebar support being snapped on a house foundation in Parkersburg too, which was pretty impressive. Overall I don’t know about this one, as it’s very dependent on the situation, the type of building, and the construction quality level.

8.) Anchor bolt shearing and removal can be highly impressive if the bolts are properly installed. But conversely, it can be a sign that the bolts weren’t installed properly or weren’t drilled deeply into the concrete. This one is also iffy and situation dependent. Falls short of the “highly reliable” bar in my book.

9.) Nope nope nope, I tossed out relatively short distance vehicle throwing as a high-end indicator a long time ago. Just like trenching and asphalt scouring, I’ve simply seen it happen too many times well below EF5 intensity. 100 meters is nothing, and heck even a couple hundred meters isn’t that crazy. I have even seen vehicles get tossed comparable distances/mangled near structures that sustained only EF2 damage (Ensign, KS 2015/Deer Park, TX 2023). Believe it or not, I witnessed a very tightly wound high-end EF1 QLCS spin-up that lofted and mangled a pickup truck in my home town. Buildings in the immediate path only had roof and window damage. Now however, if it’s something huge and very heavy like a combine, loaded train car, a massive piece of farming equipment, or a huge fertilizer tank then it’s much more impressive and absolutely a possible indicator of EF5 strength. Now with that said, I do consider thrown vehicles to be high-end indicators in some situations, but it has to be truly remarkable and extreme. What I mean by that is thrown a bare minimum of 3/4 of a mile. This may sound extreme, but that’s the point: these kinds of distances literally only happen in very high-end events. The goal is to identify things that almost exclusively happen in the most of violent tornadoes. So while a few hundred meters or so doesn’t mean much since it’s so common with your average EF4 (and sometimes occurs with EF2s and EF3s), 3/4 of a mile should be the benchmark because it’s the bare minimum distance that can be reasonably linked to very high-end events.

—————

10.) You forgot one! Concrete scouring. Super rare. Bakersfield Valley, Jarrell, El Reno/Piedmont. Almost never happens except for in high-end F5/EF5 events.

11.) Another one! Wind-rowing. Not as rock solid as others, but can sometimes still be a good hint at high-end intensity. I only really put much weight on it if it’s truly extreme (Andover, Vilonia, etc). I’ve seen moderate wind rowing below EF5 intensity. So you really need to see those massive, super long debris streaks that seemingly stretch on forever for it to be significant.

A few questions. Why was Bakersfield Valley not rated F5? It happened in 1990! Goessel gets the F5 but it doesn't? Do you think asphalt scouring could prove a better indicator if an engineering site survey is done?

 

[buckeye05]

A few questions. Why was Bakersfield Valley not rated F5? It happened in 1990! Goessel gets the F5 but it doesn't? Do you think asphalt scouring could prove a better indicator if an engineering site survey is done?

Goessel produced legit F5 damage to at least one anchor bolted home that was swept completely away, and mathematical analysis of spiral markings it left in fields reportedly proved F5 winds.

As to why Bakersfield Valley wasn’t rated F5, I’m not sure, because it produced unbelievably intense contextual damage. The only thing I can think of is maybe it came down to the fact that the house it hit wasn’t swept clean, and they didn’t want to rate it F5 without some “classic” F5 structural damage. That’s a reach though, and I’m just not sure. It should have been rated F5.

Also no, asphalt scouring is a very inconsistent and overall terrible indicator. I’ve seen low-end F2 tornadoes scour pavement while causing minimal damage to trees in the direct path.

 

[SweptSlab5]

Goessel produced legit F5 damage to at least one anchor bolted home that was swept completely away, and mathematical analysis of spiral markings it left in fields reportedly proved F5 winds.

As to why Bakersfield Valley wasn’t rated F5, I’m not sure, because it produced unbelievably intense contextual damage. The only thing I can think of is maybe it came down to the fact that the house it hit wasn’t swept clean, and they didn’t want to rate it F5 without some “classic” F5 structural damage. That’s a reach though, and I’m just not sure. It should have been rated F5.

Also no, asphalt scouring is a very inconsistent and overall terrible indicator. I’ve seen low-end F2 tornadoes scour pavement while causing minimal damage to trees in the direct path.

Do you have any photos of the F5 home? I always thought the rating was just cycloidal marks. I always thought that the analysis that was done was faulty, but I may be wrong.

 

[VultureDirge89]

Goessel produced legit F5 damage to at least one anchor bolted home that was swept completely away, and mathematical analysis of spiral markings it left in fields reportedly proved F5 winds.

As to why Bakersfield Valley wasn’t rated F5, I’m not sure, because it produced unbelievably intense contextual damage. The only thing I can think of is maybe it came down to the fact that the house it hit wasn’t swept clean, and they didn’t want to rate it F5 without some “classic” F5 structural damage. That’s a reach though, and I’m just not sure. It should have been rated F5.

Also no, asphalt scouring is a very inconsistent and overall terrible indicator. I’ve seen low-end F2 tornadoes scour pavement while causing minimal damage to trees in the direct path.

A good example of this is the Pierson, MB EF2 from 7/27/15, which scoured asphalt from a highway while leaving crops in the fields beside the highway totally untouched and only rolling vehicles instead of lofting/tossing them.

 

[Central Ohio Wx]

A good example of this is the Pierson, MB EF2 from 7/27/15, which scoured asphalt from a highway while leaving crops in the fields beside the highway totally untouched and only rolling vehicles instead of lofting/tossing them.

There's also this from the 2013 Pierson (Iowa) "EF4". Pavement was scoured, but not by the tornado itself.

 

[VultureDirge89]

When was Alonsa? I don't remember that one.

August 3, 2018.

Alonsa was mentioned in a paper as an EF5 candidate based on the long-distance movement of large hay bales. What's really weird is that from what I've seen, 2018 seems to have more EF5 candidates (Camp Crook, Douglas, Alonsa) than EF4 candidates (Laramie, maybe Tescott). As if it wasn't already one of the weirdest tornado seasons of all time.

 

[Sawmaster]

Scouring of hard surfaces depends a lot more of what's in the wind than the wind itself. Think of how a sandblaster works but with larger 'grit'. Unless you can factor that in then you can't know whether the damage was initiated or done by impact or wind alone,therefore it's not highly useful as a determinant of wind speed except as a coarse minimum speed which is known accurately through other means, below which it is never seen.

More on lofting of vehicles and heavy machinery. This is not something which is easily classified or defined as the same wind will affect different things in different ways. A large heavy sedan will not be as affected as a large relatively light vehicle with more congruent surface area for the wind to work with. A large van or a box truck when empty will give the wind more to work with and could leave a smaller lighter more rounded car relatively unaffected. Even comparing a minivan with a car of the same weight will give different results. Pick-up tricks with the light rear ends will be more easily lifted there thus exposing a far better surface fr the wind to get a grip on. Some heavy farm machinery is fairly open and won't catch as much wind as similar equipment lacking those openings.

Even Ethan Moriarty's excellent calculations for winds affecting cylindrical objects cannot possibly be perfectly accurate as the effects will greatly vary according to whether the tank or tanker car is struck only broadside versus end-on and those parameters may (probably will) change during the entirety of the event, perhaps many times. Even the more precisely calculable effects on boxcars will have that latter variability. Also the aerodynamics involved change with shape. An airplane wing will give lift due to its shape when the same-sized flat surface will not. The strong vacuum force on the far side of a cylinder in the wind dissipates rapidly with a change in angle of the wind. Winds perpendicular to a surface will have more force on the object than the same winds striking at an angle. Therefore to form any more or less 'universal' conclusions in this category clearly cannot be done with any precision and will necessarily give erroneous results. The only accurate approach is to consider the vehicle or object which is being studied individually, and then correlating any conclusions based only on very similar instances to test for accuracy..

To say that vehicle lofting cannot be used to define strong tornadoes over weaker ones is as inherently as fallacious as classifying all homes the same way. It can be done with some precision if you consider the vehicle involved and compare that only to similar cases. Empirical thinking has limits and it's conclusions are easily skewed by making presumptions of a categorical nature which are too wide. It's an easy trap to fall into because conformation biases will justify whatever conclusions you reach. How you think matters more than what you think, and if you start out thinking incorrectly then your conclusions will likely be just as wrong.

The problem with tornado studies is that a lot of our data is coming from essentially unmeasureable observations which can only be analyzed empirically so we must be very careful to not let the known problems with this kind of thinking lead us astray, and we must be ever-ready to change our previous conclusions when more certain and precise data becomes known.

 

[Grand Poo Bah]

I think we gotta come up with a name for this type of low end ground damage.... Sodding? lol

Based on the similar photos you've shared @buckeye05, it at least seems this type of low end damage has a unique presentation that can be discerned from actual scouring and trenching.

 

[tornado examiner]

LSU
loose soil uplift

Call it that.
Not a bad term for it.

 

[buckeye05]

I think we gotta come up with a name for this type of low end ground damage.... Sodding? lol

Based on the similar photos you've shared @buckeye05, it at least seems this type of low end damage has a unique presentation that can be discerned from actual scouring and trenching.

Yeah absolutely, I call this pockmarking or a debris impact mark. I’ve also seen it referred to as “ground scarring”, which is a term I hate because it often causes confusion, as it is sometimes falsely used to describe actual ground scouring. Anyway, pockmarking is different from trenching and grass scouring, and it simply occurs when a piece of debris impacts the ground. It doesn’t take a very strong tornado to do this.

Unfortunately, these three different phenomena (pockmarking, trenching, and grass scouring) aren’t always viewed as distinct, separate things caused by different mechanics within a tornado, even though that’s very much the case. This photo illustrates one of the reasons why some people are dismissive of grass scouring; because they erroneously see the above phenomenon and grass scouring as one and the same. For example, many years ago on a different site, I saw a NWS surveyor who was being dismissive of grass scouring and claimed that it could occur as low as EF2 intensity. When asked for a specific example of that happening, and he replied with an anecdote from an EF2 he surveyed in which a grain bin was thrown and slammed into the ground, removing grass at the impact point. To him, that was “grass scouring”. That’s a big problem because it shows that some people, including NWS employees, are unable to see the significant difference between a piece of debris impacting the ground, versus the complete and consistent removal of all grass along an even swath, leaving a path of bare dirt that follows the tornado’s center line. Those are two very, very different things, that occur at very different intensities, and are caused by different mechanics.

Grass scouring is not a purely debris impact related phenomenon. When debris impacts occur, you can see the individual divots and pockmarks, even if there’s a lot of them, so that doesn’t account for the smooth, even paths of bare soil seen after some high-end tornadoes. Even in cases where there clearly was a ton of debris involved, such as the Guin photo, you can see that there is just as much debris on the unscoured grass as there is on the bare soil. This to me indicates that the “smooth, even swath of bare dirt” type of grass scouring occurs independently of debris impacts, and likely is caused by a mix of high velocity particulate (sandblasting) and extreme winds within the tornado’s core literally ripping the surface vegetation from the ground.

 

[buckeye05]

I’m taking a closer look at the above photo, and after really zooming in and analyzing it, there’s a chance this might actually be an isolated spot of low-end trenching rather than a debris impact. The type of pasture ground, the lack of deep gouging, the lack of debris in the background, and the way the sod appears to have been peeled back are all consistent. If it is, it’s another great example of why I do not consider trenching to be a high-end indicator.

In any case, what I said about debris impacts marks vs. grass scouring still applies.

 

[Grand Poo Bah]

I’m taking a closer look at the above photo, and after really zooming in and analyzing it, there’s a chance this might actually be an isolated spot of low-end trenching rather than a debris impact. The type of pasture ground, the lack of deep gouging, the lack of debris in the background, and the way the sod appears to have been peeled back are all consistent. If it is, it’s another great example of why I do not consider trenching to be a high-end indicator.

In any case, what I said about debris impacts marks vs. grass scouring still applies.

That's why I said we need to come up with a name for it, because it definitely doesn't look like trenching or scouring. It's more like "sodding". Or "loose soil uplift". It seems like its own unique phenomenon and it's actually kinda fascinating! If you find your other pics of this low end phenomenon I think they all have a very similar presentation. Highly saturated loamy soil, with shallow rooted grass.

Id imagine it's still a pretty decent amount of force required to do this. I'm picturing all those videos of tiny dust devil looking tornadoes that lift cars. Like a microsecond of strong suction. The destruction of the CMU structure supports the idea. Impossible to rate though because there isn't anything close to 3 second winds. It's definitely worth discussing and theorizing about.

 

[buckeye05]

That's why I said we need to come up with a name for it, because it definitely doesn't look like trenching or scouring. It's more like "sodding". Or "loose soil uplift". It seems like its own unique phenomenon and it's actually kinda fascinating! If you find your other pics of this low end phenomenon I think they all have a very similar presentation. Highly saturated loamy soil, with shallow rooted grass.

Id imagine it's still a pretty decent amount of force required to do this. I'm picturing all those videos of tiny dust devil looking tornadoes that lift cars. Like a microsecond of strong suction. The destruction of the CMU structure supports the idea. Impossible to rate though because there isn't anything close to 3 second winds. It's definitely worth discussing and theorizing about.

Yeah what you’re describing is literally just trenching from a lower intensity tornado. I’m 90% sure that’s what this is, so that wouldn’t be a separate phenomenon (sod and grass being dug up and peeled back by a tight circulation). It’s the same phenomenon just on a smaller scale. If a stronger tornado occurred over that same pasture, it would have almost certainly been plowed up in a more dramatic fashion.

 

[WeathermanLeprechaun]

I think we gotta come up with a name for this type of low end ground damage.... Sodding? lol

Based on the similar photos you've shared @buckeye05, it at least seems this type of low end damage has a unique presentation that can be discerned from actual scouring and trenching.

I did not see this being mentioned in this thread, I don't really keep up with this thread often, but yeah, once again a great indicator that trenching can happen as low as EF1.

 

[WeathermanLeprechaun]

I'm just gonna leave these here. Two different extremes...




Don't snort Pixy Stix, fellas.

I am very sure this is just engagement farming. The moderators took a little break and sometimes people intentionally bait others for drama and controversy with comments like these. It's pretty confusing but i just wouldn't pay attention to these posts whatsoever.

 

[WeathermanLeprechaun]

Exactly, and if you aren't amazed when you consider that feat it's a you problem. Not only this, but some of the most experienced and seasoned weather scientists were "impressed" by it, so what does it matter if some edgy kids in a Discord server aren't? It's a completely meaningless argument, and a level of self importance that is laughable.

I'll take it a step further and say my unpopular opinion is that I don't really care how seasoned of a professional it is, if they say something a tornado did was "not impressive" they immediately lose credibility to me. Why would you openly advertise such a lack of objectivity?

How many people were impressed by the grain cars in Enderlin? Almost none. Yet that feat required 260 mph winds. How many people have discounted the safe that was thrown in Rainsville for years, yet a recently released compact objects study proved winds FAR exceeding 200 mph were required to do that. It's so wild to me that surveying tornado damage has basically become a vibe check, and it's such a commonly accepted practice. At least TRY to be scientific!

Anyways, sorry for the sassiness. Thanks for coming to my Ted Talk. Rant over.

I really agree and i also used to think the grain cars in Enderlin wasn't impressive. I mostly followed the herd though and general opinion back then and I've tried to lessen a lot of that in the past few months.

People think St John's Hospital being as structurally damaged as it was wasn't too impressive because it's not a traditional building. No EF5 will tear that whole thing down but it being structurally compromised is extremely impressive. It's why the grain cars didn't seem interesting to many. It's not a traditional EF5 DI, and it's not a well constructed building being swept a way with very strong anchor bolts. Same thing with the hospital. It's not really a traditional EF5 DI and people view EF5 damage as something being gone, or erased whereas those things still existed but EF5 damage was done to them in different ways. Inpressiveness is not how it works though and you're 100% right.

 

[Kds86z]

I am very sure this is just engagement farming. The moderators took a little break and sometimes people intentionally bait others for drama and controversy with comments like these. It's pretty confusing but i just wouldn't pay attention to these posts whatsoever.

I have seen a YouTube video link where smithsville is called most powerful tornado ever. Never watched it. Neither agree nor disagree as I don’t know enough.

 

[WeathermanLeprechaun]

I have seen a YouTube video link where smithsville is called most powerful tornado ever. Never watched it. Neither agree nor disagree as I don’t know enough.

Well, you can make a argument. But half of that subreddit was calling Hackleburg a EF4 for intentional drama which i found weird. I think i should keep a lot of that dumpfire out of here and not ruin the thread.

Opinions are subjective but there are opinions where there really isn't a reason to even have it. Smithville was extremely impressive in town and is definitely up there with some of the strongest.

 

[Grand Poo Bah]

Yeah what you’re describing is literally just trenching from a lower intensity tornado. I’m 90% sure that’s what this is, so that wouldn’t be a separate phenomenon (sod and grass being dug up and peeled back by a tight circulation). It’s the same phenomenon just on a smaller scale. If a stronger tornado occurred over that same pasture, it would have almost certainly been plowed up in a more dramatic fashion.

Scouring of hard surfaces depends a lot more of what's in the wind than the wind itself. Think of how a sandblaster works but with larger 'grit'. Unless you can factor that in then you can't know whether the damage was initiated or done by impact or wind alone,therefore it's not highly useful as a determinant of wind speed except as a coarse minimum speed which is known accurately through other means, below which it is never seen.

More on lofting of vehicles and heavy machinery. This is not something which is easily classified or defined as the same wind will affect different things in different ways. A large heavy sedan will not be as affected as a large relatively light vehicle with more congruent surface area for the wind to work with. A large van or a box truck when empty will give the wind more to work with and could leave a smaller lighter more rounded car relatively unaffected. Even comparing a minivan with a car of the same weight will give different results. Pick-up tricks with the light rear ends will be more easily lifted there thus exposing a far better surface fr the wind to get a grip on. Some heavy farm machinery is fairly open and won't catch as much wind as similar equipment lacking those openings.

Even Ethan Moriarty's excellent calculations for winds affecting cylindrical objects cannot possibly be perfectly accurate as the effects will greatly vary according to whether the tank or tanker car is struck only broadside versus end-on and those parameters may (probably will) change during the entirety of the event, perhaps many times. Even the more precisely calculable effects on boxcars will have that latter variability. Also the aerodynamics involved change with shape. An airplane wing will give lift due to its shape when the same-sized flat surface will not. The strong vacuum force on the far side of a cylinder in the wind dissipates rapidly with a change in angle of the wind. Winds perpendicular to a surface will have more force on the object than the same winds striking at an angle. Therefore to form any more or less 'universal' conclusions in this category clearly cannot be done with any precision and will necessarily give erroneous results. The only accurate approach is to consider the vehicle or object which is being studied individually, and then correlating any conclusions based only on very similar instances to test for accuracy..

To say that vehicle lofting cannot be used to define strong tornadoes over weaker ones is as inherently as fallacious as classifying all homes the same way. It can be done with some precision if you consider the vehicle involved and compare that only to similar cases. Empirical thinking has limits and it's conclusions are easily skewed by making presumptions of a categorical nature which are too wide. It's an easy trap to fall into because conformation biases will justify whatever conclusions you reach. How you think matters more than what you think, and if you start out thinking incorrectly then your conclusions will likely be just as wrong.

The problem with tornado studies is that a lot of our data is coming from essentially unmeasureable observations which can only be analyzed empirically so we must be very careful to not let the known problems with this kind of thinking lead us astray, and we must be ever-ready to change our previous conclusions when more certain and precise data becomes known.

The really good thing about the compact objects study is they used actual models to simulate all sorts of wind directions, speeds, and durations thousands of times, and then plotted the results on a bell curve. Highly recommend reading up on their methodology, and I hope they continue to expand on their research.

 

[Grand Poo Bah]

Yeah what you’re describing is literally just trenching from a lower intensity tornado. I’m 90% sure that’s what this is, so that wouldn’t be a separate phenomenon (sod and grass being dug up and peeled back by a tight circulation). It’s the same phenomenon just on a smaller scale. If a stronger tornado occurred over that same pasture, it would have almost certainly been plowed up in a more dramatic fashion.

Sure, but that's just what damage intensity means. If you want to call it trenching that's fine, but sod being peeled up in loose soil can't be considered the same thing as 12 inch deep trenches lol. The depth of the trench is a major factor.

In the same vein as what you were saying about judging contextual indicators based on experience, how often do you seen 8+ inch trenches? I can't remember how deep they were in the photos you shared a while back.