Severe WX December 10 & 11, 2021 Severe Threat (4 Viewers)

buckeye05

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Oooh ok I see what you’re saying and I agree. Regarding the discrepancy between the construction and context in Cambridge Shores, your guess is as good as mine. I’d infer the failure point was somewhere within the house structure itself, rather than the foundation and anchoring mechanisms. But since the homes were obliterated, we’ll never know what that potential failure point was.
 

pohnpei

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To clarify, I was NOT trying to say that every well constructed home swept away should be rated EF5. My point is that damage surveys should focus more on contextual damage and other types of structures rather than just homes. If a tornado causes extreme contextual damage and a well-constructed home is swept away to compliment that damage, then yes, it's a clear cut EF5.

This has been said before, but most US homes are constructed like crap and it's pretty much a "matter of chance" as to whether or not a tornado will hit a home capable of indicating such a rating, at peak intensity likewise.

I do have to wonder why the area with the best home construction (Cambridge Shores) had among the weakest contextual damage along the entire path though. Bizarre to say the least.
I don't think the contextual in Cambridge Shore was among the weakest along the path. Except several impressive vehicle damage in Mayfield's factory area,the vehicle damage and debarking was quite constant through its path. Like there's no real mangled vehicles or totally debarked trees in Dawson Springs or Princeton. Bremen also didn't have more debarking than Cambridge Shore.
 

TH2002

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Oooh ok I see what you’re saying and I agree. Regarding the discrepancy between the construction and context in Cambridge Shores, your guess is as good as mine. I’d infer the failure point was somewhere within the house structure itself, rather than the foundation and anchoring mechanisms. But since the homes were obliterated, we’ll never know what that potential failure point was.
If I had to come up with an explanation, my guess would be that the wider swath of destructive winds (probably mostly consisting of winds in the mid EF3 to lower EF4 range) swept away block foundation homes and swept homes from their subfloors, while brief but violent subvortices caused spotty debarking and totally swept away a couple homes taking the subflooring with, including that one large lakeside home.

One tornado that immediately came to mind in this regard is the 1987 Glade tornado. That tornado slabbed at least one well-built, anchor bolted brick veneer home, though there are no photos showing anything remarkable as far as contextual damage goes. With that said the Glade tornado is not exactly well documented, though in the photos @locomusic01 posted recently, including some that appear to have been taken in pretty intense swaths of damage, you would think there would AT LEAST be some spotty debarking.
 
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Oooh ok I see what you’re saying and I agree. Regarding the discrepancy between the construction and context in Cambridge Shores, your guess is as good as mine. I’d infer the failure point was somewhere within the house structure itself, rather than the foundation and anchoring mechanisms. But since the homes were obliterated, we’ll never know what that potential failure point was.

I think what this boils down to is just a fundamental difference of opinion on how the scale should be applied.

For me, and I think several others on here, it ought to be "Ok, we have a well-built, anchored house that was leveled and swept away in classic F5 fashion. Prove to me that it wasn't EF5." Instead, the practice seems to be to seize on any explanation to assign a lower rating, such as the house could have been struck by debris from upstream. It could have failed somewhere other than at the foundation anchoring (even if the evidence that could prove this is ground into shards and wind-rowed for half a mile).

The EF-scale was supposed to have a linear 1:1 relationship with the old F-scale, however in practice that's clearly not the case. I share the concern expressed by others on here that if we go with the absolute "pure" definition of EF5 damage, in that everything has to be perfect in terms of construction and context and it has to be somehow definitely proven beyond a shadow of a doubt (remember, in the presence of essentially complete devastation) that the damage could not have been caused by anything other than winds exceeding 200 MPH, then EF5 ratings will become so vanishingly rare that they might as well not exist. In terms of being able to use the scale to understand the climatology of the most violent 0.5% of so tornadoes that occur on the planet, we're really not that much better off than the days of grad students retroactively rating tornadoes by poring over grainy newspaper photos.
 

Sawmaster

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I am enjoying the discussion. We all know tornadoes can do bizarre things, which is why we need to allow for more than just checking boxes on a DI page to assess them. It seems everyone here has found something contentious about the rating of this tornado where what is clear to us wasn't clear to those who did the survey. I'm not in any position to cause things to change but I gather some of you might be placed where you can at least attempt to get the problems with the current methodology of damage assessment to more closely match reality, even when it's not a ckeck-box item. I hope you'll do that, for it's clear that it is needed.

Now back to the Omaha hail...

Phil
 

buckeye05

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I think what this boils down to is just a fundamental difference of opinion on how the scale should be applied.

For me, and I think several others on here, it ought to be "Ok, we have a well-built, anchored house that was leveled and swept away in classic F5 fashion. Prove to me that it wasn't EF5." Instead, the practice seems to be to seize on any explanation to assign a lower rating, such as the house could have been struck by debris from upstream. It could have failed somewhere other than at the foundation anchoring (even if the evidence that could prove this is ground into shards and wind-rowed for half a mile).

The EF-scale was supposed to have a linear 1:1 relationship with the old F-scale, however in practice that's clearly not the case. I share the concern expressed by others on here that if we go with the absolute "pure" definition of EF5 damage, in that everything has to be perfect in terms of construction and context and it has to be somehow definitely proven beyond a shadow of a doubt (remember, in the presence of essentially complete devastation) that the damage could not have been caused by anything other than winds exceeding 200 MPH, then EF5 ratings will become so vanishingly rare that they might as well not exist. In terms of being able to use the scale to understand the climatology of the most violent 0.5% of so tornadoes that occur on the planet, we're really not that much better off than the days of grad students retroactively rating tornadoes by poring over grainy newspaper photos.
The problem with that is that the scale wasn't actually designed so that a slabbed, bolted-down home would receive an assumed EF5 rating just based on those two factors alone. This is because the scale lists the expected wind speed for a slabbed home at 200 MPH, which is actually EF4. Unless the construction is exceptional, this leaves contextual evidence as the single distinguishing factor between EF4 and EF5 when it comes to homes. As a result, there isn't a single EF5-rated tornado that received such a rating just based on only those two factors (bolts and a clean sweep). Each one was accompanied by extreme contextual damage, even Greensburg. Deeming the damage in Cambridge Shores EF5 would break that precedent, and it would be the first EF5 tornado to be rated purely based on just house construction with no extreme contextual damage.

It's really more about how the scale was set up and meant to be used than opinion. Now with that said, there have been multiple events that met both the contextual and structural requirements for EF5, and still got EF4 (Vilonia, Goldsby, Chapman, ect), and that is where I start to take issue. Cambridge Shores doesn't quite cross that threshold though.
 
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TH2002

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I would have settled with a marginal EF5 rating for Cambridge Shores considering the homes were well constructed but context wouldn't support anything higher, and I think that's an appropriate upper bound rating. I can't call it clear cut EF5 by any stretch though, and high end EF4 would have probably been the most appropriate.

In terms of damage surveying, Bremen is essentially the parallel to Phil Campbell 2011 if you think about it. All the context screaming EF5 was there in both cases, but there may very well have not been a single structure well constructed enough to support an EF5 rating in the town of Phil Campbell (except probably the slabbed apartment building, which I wish there were ground level photos of). In Bremen we already know such was definitely the case.
 
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buckeye05

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I would have settled with a marginal EF5 rating for Cambridge Shores considering the homes were well constructed but context wouldn't support anything higher, and I think that's an appropriate upper bound rating. I can't call it clear cut EF5 by any stretch though, and high end EF4 would have probably been the most appropriate.

In terms of damage surveying, Bremen is essentially the parallel to Phil Campbell 2011 if you think about it. All the context screaming EF5 was there in both cases, but there may very well have not been a single structure well constructed enough to support an EF5 rating in Phil Campbell (except probably the slabbed apartment building, which I wish there were ground level photos of). In Bremen we already know such was definitely the case.
Then you would be breaking the guidelines of the scale. Like I said, good house construction brings it up to a maximum of 200 MPH per the guidelines, but you can't go higher than that without contextual support. That's not my opinion, that is how the scale was intentionally designed. That 200 MPH designation for expected damage was established to specifically avoid assignment of EF5 ratings based on the exact kind of scenario bolded above in your quote. The only exception is when the construction is truly above and beyond, which it wasn't in Cambridge Shores. So with it established that none of the homes in Cambridge Shores meet either of those criteria, then how are you arriving at a conclusion of low-end EF5?

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CalebRoutt

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Then you would be breaking the guidelines of the scale. Like I said, good house construction brings it up to a maximum of 200 MPH per the guidelines, but you can't go higher than that without contextual support. That's not my opinion, that is how the scale was intentionally designed. That 200 MPH designation for expected damage was established to specifically avoid assignment of EF5 ratings based on the exact kind of scenario bolded above in your quote. The only exception is when the construction is truly above and beyond, which it wasn't in Cambridge Shores. So with it established that none of the homes in Cambridge Shores meet either of those criteria, then how are you arriving at a conclusion of low-end EF5?
I think you’re being a little “nit-picky” here. I personally would be fine with EF4 190 for Cambridge Shores, but the damage in Bremen overwhelmingly screams EF5 205-210 mph. The tornado was probably EF5 fairly consistently from Princeton to Bremen. I personally saw severe debris granulation of multiple rows of homes/multi-story apartment buildings there in addition to severe tree debarking. In terms of vehicle damage, there was. Keep in mind Greensburg didn’t toss too many cars.

Again, I applaud you for asking great questions, but the fact of the matter is that this tornado caused classic EF5 contextual damage, but many structures weren’t well built.
 

buckeye05

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I think you’re being a little “nit-picky” here. I personally would be fine with EF4 190 for Cambridge Shores, but the damage in Bremen overwhelmingly screams EF5 205-210 mph. The tornado was probably EF5 fairly consistently from Princeton to Bremen. I personally saw severe debris granulation of multiple rows of homes/multi-story apartment buildings there in addition to severe tree debarking. In terms of vehicle damage, there was. Keep in mind Greensburg didn’t toss too many cars.

Again, I applaud you for asking great questions, but the fact of the matter is that this tornado caused classic EF5 contextual damage, but many structures weren’t well built.
I'm really not. While EF5-consistent contextual damage did occur in Bremen, it at no point overlapped with any construction that would qualify for EF5. Those were CMU foundation homes in Bremen, which recent EF scale presentations and surveys have established as non-eligible for EF5. You can't just say "Ok the construction here was good, but the context was lacking (Cambridge Shores), but elsewhere there was insane contextual damage, but poor construction was present (Bremen). The two criteria didn't overlap, but close enough." Those two criteria absolutely HAVE to overlap in at least one area along the path for EF5. That didn't happen at any point along the path of the Mayfield tornado.

Was Mayfield/Bremen an EF5? Almost certainly. Did it produce damage that met the criteria for BOTH construction and contextual support in at least one area? No it did not. There's a difference between a tornado that was clearly capable of producing EF5 damage, and tornado that actually produces damage that meets the EF5 criteria. Mayfield falls into the first category, but not the latter.

Had this one occurred on 4/27/2011, it may have had a shot, but the days of context-based EF5s are over, meaning won't have another Rainsville type EF5 where a bunch of frail CMU foundation homes were obliterated, but they go with EF5 rating based on context. Do I agree with that? Not really, but I don't set the standards or make the rules when it comes to EF scale application, and I do understand the disqualification of CMU foundation homes from EF5 eligibility.
 

TH2002

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Then you would be breaking the guidelines of the scale. Like I said, good house construction brings it up to a maximum of 200 MPH per the guidelines, but you can't go higher than that without contextual support. That's not my opinion, that is how the scale was intentionally designed. That 200 MPH designation for expected damage was established to specifically avoid assignment of EF5 ratings based on the exact kind of scenario bolded above in your quote. The only exception is when the construction is truly above and beyond, which it wasn't in Cambridge Shores. So with it established that none of the homes in Cambridge Shores meet either of those criteria, then how are you arriving at a conclusion of low-end EF5?
I didn't. Refer to "I can't call it clear cut EF5 by any stretch though, and high end EF4 would have probably been the most appropriate."

I am saying that if Cambridge Shores HAD been rated marginal EF5, I wouldn't have made a big deal over it.

I also have my own ideas as to how tornadoes should be rated, and yes, I do break the guidelines of the scale sometimes. If I didn't then I would confidently say things like "the Hackleburg tornado was at EF4 intensity in Phil Campbell" and "Rainsville was an EF4". Again trying to illustrate my point, I 100% agree that Hackleburg was still at EF5 intensity in Phil Campbell despite the mostly poor construction in that town, and would even go as far as to rate that one CMU foundation house EF5 due to overwhelming supporting context.

I honestly think contextual damage and other non-standard DI's should be considered just as much, if not MORE than home damage, especially as far as higher-end tornadoes are concerned. Using that logic, I would also disagree with someone if they said that Cambridge Shores was solid EF5.
 

buckeye05

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Gotcha. I know it really does seem like annoying, pedantic nitpicking coming from me right now, I get it. I'm honestly not trying to be a pain in the @ss. But, in order to have some degree of credibility when discussing ratings, it is important to follow the scale as it was intended to be implemented. With that said, some surveyors also break the guidelines, but the people who set the guidelines weren't just pulling random numbers out of a hat for the wind speed estimates, and I don't think anyone should go above or below the upper and lower bound limitations set in place unless they have some serious credentials or evidence to go against the already established estimates, be it NWS employees or weather geeks on the internet.

Mayfield highlights an important issue. How do we deal with situations where the tornado was clearly stronger than the applied rating, but there isn't a single point of damage to definitively prove it? It's tricky. The only solution I can think of would the addition of supplementary contextual damage scale that could be used to "fine tune" a rougher estimate set in place by structural damage/engineering analysis. The car scale that is about to be added is a step in that direction though, so I'm cautiously hopeful.
 

Sawmaster

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So an EF-5 blows away a well-consructed properly bolted house which happens to sit in a grassland without trees or shrubbery or powerpoles and somehow it's not an EF-5. That doesn't make sense does it?

If that supposed house can bring only a 200MPH rating we know that was the minimum winds it received, not the maximum. Same house same winds except now we have denuded shrubbery, debarked and broken trees, uprooted trees and shrubs, and powerpoles snapped off at the ground so it's an EF-5 instead. That doesn't make any sense either because it was the exact same wind affecting the exact same house and it cannot be both ratings at the same time.

And before someone comes along saying that I don't understand the system, I will point out that I do understand it- every bit of it (along with official pointers on using it properly) is publicly available and I've pored over it thoroughly. That's why I can clearly see that the problem is systemic and the truth clearly cannot always be found using that system.

Phil
 
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when it comes to shrubbery damage...the Pembroke tornado on April 5 this year did damage some. noticeably tilting a few thick bushes next to the slabbed homes.
 

buckeye05

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So an EF-5 blows away a well-consructed properly bolted house which happens to sit in a grassland without trees or shrubbery or powerpoles and somehow it's not an EF-5. That doesn't make sense does it?

If that supposed house can bring only a 200MPH rating we know that was the minimum winds it received, not the maximum. Same house same winds except now we have denuded shrubbery, debarked and broken trees, uprooted trees and shrubs, and powerpoles snapped off at the ground so it's an EF-5 instead. That doesn't make any sense either because it was the exact same wind affecting the exact same house and it cannot be both ratings at the same time.

And before someone comes along saying that I don't understand the system, I will point out that I do understand it- every bit of it (along with official pointers on using it properly) is publicly available and I've pored over it thoroughly. That's why I can clearly see that the problem is systemic and the truth clearly cannot always be found using that system.

Phil
Well if it was a legit EF5 and the setting was grassland, there would at least be ground scouring to analyze. Plus there are also other contextual factors that can be looked at in that scenario such as debris patterns (extreme wind rowing? no traceable debris? either of those could be used as support for EF5, even in a desolate empty area). Almost every home has vehicles too, so their movement (or lack there of) would also be looked at. I hear what you are saying, and its an interesting hypothetical scenario, but not a realistic one, and I can't actually think of anything like that actually happening IRL. If there's an EF5, there will almost always be SOME non-structural indicators left behind to suggest extreme intensity and factor in, unless the tornado spends its whole life over a body of water or something.

But overall, what you are describing is the main flaw of the scale. It's based on damage, so we can only assign wind speed estimates what we can prove (via engineering), or strongly correlate via contextual hallmarks associated with various tornado intensities (accomplished by statistically comparing degrees of contextual damage in the immediate vicinity of more provable wind speeds derived from destroyed structures, such as the AMS debarking study that was done after Moore 2013). Unfortunately, the only way to accurately ascertain the true intensity maxima of a tornado is though mobile radar, and we all know the unfortunate status of that in relation to tornado ratings. The current implementation of the is EF scale far from perfect, but if we want stick with hard evidence and facts, the engineering/context approach is as close as we can get for the time being.

Also personally, I'd rather have a tornado in the books as a definitive, proven EF4, than a possible, maybe EF5.
 
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pohnpei

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For structure damage rating system, I actually have some questions or namely confusion here. One question would be If we can rate tornados based on structure damage, is It possible for hurricane? It's entirely possible and have been put into practice. Since we now have pretty reliable tools to measure hurricane winds so we can compare it with different damage indicator to see whether It's well matched up.
This was the Hope Town, the first landfall place of hurricane Dorian with sustained winds of 185mph and gust easily topped 200mph. There were mainly wood frame houses wIth hurricane straps possiblely. As we can see, most houses had their roofs largely intact and I don't think anyone can tell the difference here from a normal cat4 level hurricane based on structure damage alone. I don't know If these roof structures were designed to hold over 200mph winds but one thing I want to point here was the error range can be really big in hurricane's strength measurement when compared It to other more reliable tools. But one Interesting to notice is the vegatation damage can be fairly good and reliable in hurricane's wind measurement based on large amounts of past cases.

Tornados are different animals. When radar can be one of the most perfect tools to measure hurricane's winds, even mobile radar with 30m range solution is far from perfect to measure tornados's winds. Tornado's inflow layer are too shallow and strongest winds are
too close to the ground and debris/hail/beam blockage can siginificantly contaminate data which happened in almost every case. Also there's no wind height transition ratio in tornados. So there's a reason why people in office hesitate to put mobile radar winds into practice though those were already most valuable things on hand.
 
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CalebRoutt

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I'm really not. While EF5-consistent contextual damage did occur in Bremen, it at no point overlapped with any construction that would qualify for EF5. Those were CMU foundation homes in Bremen, which recent EF scale presentations and surveys have established as non-eligible for EF5. You can't just say "Ok the construction here was good, but the context was lacking (Cambridge Shores), but elsewhere there was insane contextual damage, but poor construction was present (Bremen). The two criteria didn't overlap, but close enough." Those two criteria absolutely HAVE to overlap in at least one area along the path for EF5. That didn't happen at any point along the path of the Mayfield tornado.

Was Mayfield/Bremen an EF5? Almost certainly. Did it produce damage that met the criteria for BOTH construction and contextual support in at least one area? No it did not. There's a difference between a tornado that was clearly capable of producing EF5 damage, and tornado that actually produces damage that meets the EF5 criteria. Mayfield falls into the first category, but not the latter.

Had this one occurred on 4/27/2011, it may have had a shot, but the days of context-based EF5s are over, meaning won't have another Rainsville type EF5 where a bunch of frail CMU foundation homes were obliterated, but they go with EF5 rating based on context. Do I agree with that? Not really, but I don't set the standards or make the rules when it comes to EF scale application, and I do understand the disqualification of CMU foundation homes from EF5 eligibility
I'm really not. While EF5-consistent contextual damage did occur in Bremen, it at no point overlapped with any construction that would qualify for EF5. Those were CMU foundation homes in Bremen, which recent EF scale presentations and surveys have established as non-eligible for EF5. You can't just say "Ok the construction here was good, but the context was lacking (Cambridge Shores), but elsewhere there was insane contextual damage, but poor construction was present (Bremen). The two criteria didn't overlap, but close enough." Those two criteria absolutely HAVE to overlap in at least one area along the path for EF5. That didn't happen at any point along the path of the Mayfield tornado.

Was Mayfield/Bremen an EF5? Almost certainly. Did it produce damage that met the criteria for BOTH construction and contextual support in at least one area? No it did not. There's a difference between a tornado that was clearly capable of producing EF5 damage, and tornado that actually produces damage that meets the EF5 criteria. Mayfield falls into the first category, but not the latter.

Had this one occurred on 4/27/2011, it may have had a shot, but the days of context-based EF5s are over, meaning won't have another Rainsville type EF5 where a bunch of frail CMU foundation homes were obliterated, but they go with EF5 rating based on context. Do I agree with that? Not really, but I don't set the standards or make the rules when it comes to EF scale application, and I do understand the disqualification of CMU foundation homes from EF5 eligibility.
There were numerous well-built block homes in the 2011 tornadoes that were rated EF5. There was also numerous examples of EF5 contextual damage in Cambridge Shores and in Bremen. Large trees that are snapped or sheared to near ground level and/or debarked is essentially what Tuscaloosa did in eastern Tuscaloosa county when it was likely EF5. The NWS in Paducah literally said the damage in Bremen would’ve been rated EF5 had there not been for 1 tree standing (which I cannot find). Even Tim Marshall himself said this tornado would’ve been rated EF5 if there was a missing attachment on the apartments in Dawson Springs. Again, I applaud you for holding an opinion despite multiple pieces of evidence among damage surveyors who say otherwise.
 

buckeye05

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There were numerous well-built block homes in the 2011 tornadoes that were rated EF5. There was also numerous examples of EF5 contextual damage in Cambridge Shores and in Bremen. Large trees that are snapped or sheared to near ground level and/or debarked is essentially what Tuscaloosa did in eastern Tuscaloosa county when it was likely EF5. The NWS in Paducah literally said the damage in Bremen would’ve been rated EF5 had there not been for 1 tree standing (which I cannot find). Even Tim Marshall himself said this tornado would’ve been rated EF5 if there was a missing attachment on the apartments in Dawson Springs. Again, I applaud you for holding an opinion despite multiple pieces of evidence among damage surveyors who say otherwise.
But that doesn’t address the fact that the strongest construction and contextual evidence did not overlap. You absolutely have to have both of those in one area to qualify for EF5, not just one or the other, and the debarking/car damage in Cambridge Shores was not EF5-tier. Also, not a single NWS surveyor or engineer said it should have been rated EF5. They said it would have save for a few negating factors. “Would have” does not equal “should have”. A tornado being capable of producing EF5 damage (it was), is different from a tornado actually producing damage that meets the EF5 criteria (which it did not).

I’ll keep it brief, but while CMU foundations were EF5 eligible back in 2011, they aren’t anymore, and it’s been stated in multiple recent AMS studies and damage survey presentations covering events such as Dalton, MN and Princeton, KY. That is current surveying policy from reliable sources, not just my opinion (in fact, I think in truly extreme cases, EF5 should be possible for CMU foundation homes, like Rainsville).
 
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CalebRoutt

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But that doesn’t address the fact that the strongest construction and contextual evidence did not overlap. You absolutely have to have both of those in one area to qualify for EF5, not just one or the other, and the debarking/car damage in Cambridge Shores was not EF5-tier. Also, not a single NWS surveyor or engineer said it should have been rated EF5. They said it would have save for a few negating factors. “Would have” does not equal “should have”. A tornado being capable of producing EF5 damage (it was), is different from a tornado actually producing damage that meets the EF5 criteria (which it did not).

I’ll keep it brief, but while CMU foundations were EF5 eligible back in 2011, they aren’t anymore, and it’s been stated in multiple recent AMS studies and damage survey presentations covering events such as Dalton, MN and Princeton, KY. That is current surveying policy from reliable sources, not just my opinion (in fact, I think in truly extreme cases, EF5 should be possible for CMU foundation homes, like Rainsville).
The contextual damage at Cambridge Shores was most certainly EF5. Trees either completely debarked or shredded to near or at ground level, multiple homes swept in addition to severe debris granulation. Photo below.

The Bremen home wasn’t just a block home. There was a portion around the storm shelter that was a concrete foundation and was well bolted. That portion was swept to its slab. There is literally a home of similar structure that is still in the EF-Scale manual for EF5, thus a home (if well anchored) can be rated EF5.
 

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MNTornadoGuy

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The contextual damage at Cambridge Shores was most certainly EF5. Trees either completely debarked or shredded to near or at ground level, multiple homes swept in addition to severe debris granulation. Photo below.

The Bremen home wasn’t just a block home. There was a portion around the storm shelter that was a concrete foundation and was well bolted. That portion was swept to its slab. There is literally a home of similar structure that is still in the EF-Scale manual for EF5, thus a home (if well anchored) can be rated EF5.
If only a small portion of the structure as bolted down to a concrete slab then that does not make it an EF5 candidate, the entire structure needs to be bolted to a concrete foundation for that.
 
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