Significant Tornado Events

[HAwkmoon]

Look a few years ago I'd have agreed with you, but now I'm doubtful. They seem to be both very insistent that any 'flaw' in the land path means it can't be EF5 and very nitpicky about potential flaws to the point of conjecture. It's like they don't recognise that the load path has to fail somewhere.

I recently read the actual survey report on the Elie F5. They decided to go with F5 because they thought the position of the sill plate showed it had been pulled upwards and that meant there was a good connection, rather than the more common situation of a weak connection that separates easily. Under EF scale practice I don't see that being accepted.

The home in Oak Grove would certainly get EF-5, they haven't been that strict, its just we have never had a blatantly obvious EF-5 since Moore 2013.

 

[Sawmaster]

I've seen a few instances where bolted and washered plates were pulled, but because there were no toe-nails they got an EF-4. That's more proof that they've lost sight of the goal. IIRC the latest of these I saw was Bremen or Cambridge Shores, but there might be a newer instance I'm missing. Clearly when a plate pulls away the connection to the studs was strong enough regardless of how that connection was accomplished, but their insistance of only checking off boxes on a list doesn't let them see their own stupidity.

They couldn't pull that malarky on the house in question as the corners were attached together with metal brackets and some studs between were strapped too. Strap ties connected the second floor down to the studs below and above. Look into what's done in SoCal to meet seismic codes and you'll see what I mean. The wood almost has to shred before it can pull loose from these devices.

 

[Juliett Bravo Kilo]

The home in Oak Grove would certainly get EF-5, they haven't been that strict, its just we have never had a blatantly obvious EF-5 since Moore 2013.

Yeah, we've had plenty of obvious EF5s since Moore 2013, you clearly aren't familiar with Vilonia 2014 or Chapman, KS 2016.
Really weird there are people out there that still think the EF scale is being used reliably at this point.

 

[A Guy]

I've seen a few instances where bolted and washered plates were pulled, but because there were no toe-nails they got an EF-4. That's more proof that they've lost sight of the goal. IIRC the latest of these I saw was Bremen or Cambridge Shores, but there might be a newer instance I'm missing. Clearly when a plate pulls away the connection to the studs was strong enough regardless of how that connection was accomplished, but their insistance of only checking off boxes on a list doesn't let them see their own stupidity.

They couldn't pull that malarky on the house in question as the corners were attached together with metal brackets and some studs between were strapped too. Strap ties connected the second floor down to the studs below and above. Look into what's done in SoCal to meet seismic codes and you'll see what I mean. The wood almost has to shred before it can pull loose from these devices.

Then I have to go back to my prior objections - what's the point of defining EF5 so that it can only by hitting a house build to a standard only 0.05% in the tornado-prone area actually achieve? It's not a secret that seismic or hurricane resistant construction are rare outside of areas zoned for that.

I'd also add that the ASCE - managed plenty of objections to hurricane resistant housing in the 2022 Arabi tornado.

 

[TH2002]

Then I have to go back to my prior objections - what's the point of defining EF5 so that it can only by hitting a house build to a standard only 0.05% in the tornado-prone area actually achieve? It's not a secret that seismic or hurricane resistant construction are rare outside of areas zoned for that.

I'd also add that the ASCE - managed plenty of objections to hurricane resistant housing in the 2022 Arabi tornado.

All I'm going to say to that study is this: if your background is 100% engineering and 0% meteorology, please just stay away from tornado damage surveys. That's exactly how the same organization slapped Joplin with a low-end EF4 rating.

 

[TH2002]

The home in Oak Grove would certainly get EF-5, they haven't been that strict, its just we have never had a blatantly obvious EF-5 since Moore 2013.

*cough cough* Vilonia

Fairdale and Chapman definitely should have been rated EF5 as well. When you think about it, Chapman caused very similar damage to Hackleburg and is pretty much proof that the latter wouldn't get rated EF5 today, unless maybe it happened in NWS Jackson's WFO.

DGX is definitely the only WFO that takes getting EF ratings correct as seriously as they do, and such presents another problem - the quality of a tornado's rating is more dependent on which WFO it happened in than the actual intensity of the storm. Rolling Fork would have probably gotten slapped with a high-end EF3 rating if it happened in NWS Lubbock's forecast area, for example.

 

[HAwkmoon]

Yeah, we've had plenty of obvious EF5s since Moore 2013, you clearly aren't familiar with Vilonia 2014 or Chapman, KS 2016.
Really weird there are people out there that still think the EF scale is being used reliably at this point.

Neither were as clear cut as Moore, both Chapman and Vilonia were 100% EF-5 strength, but neither have as reliable EF-5 dis.

 

[HAwkmoon]

All I'm going to say to that study is this: if your background is 100% engineering and 0% meteorology, please just stay away from tornado damage surveys. That's exactly how the same organization slapped Joplin with a low-end EF4 rating.

They did not. Engineering is a major part, that organisation, or ASCE study looked at 150-200 homes, and found no EF-5 damage. Which is totally understandable given the tiny sample of structures they looked at. Marshal who surveyed 7,200 found 22 homes with EF-5 damage. I really get annoyed when people get that study out of context which a lot of people tend to do with tornado information. I agree that there needs to be a balance between meteorology and engineering.

 

[TH2002]

Neither were as clear cut as Moore, both Chapman and Vilonia were 100% EF-5 strength, but neither have as reliable EF-5 dis.

The house in Vilonia that had both its exterior and interior walls bolted down, and the well constructed homes in Chapman (one of which was swept away with such force that a part of its poured concrete foundation was snapped, and another that basically disappeared with no debris remaining) seem like pretty reliable EF5 DI's to me.

They did not. Engineering is a major part, that organisation, or ASCE study looked at 150-200 homes, and found no EF-5 damage. Which is totally understandable given the tiny sample of structures they looked at. Marshal who surveyed 7,200 found 22 homes with EF-5 damage. I really get annoyed when people get that study out of context which a lot of people tend to do with tornado information. I agree that there needs to be a balance between meteorology and engineering.

Even taking the small sample size into consideration, the point of that study was still this: from a 'pure' engineering perspective, there were very few to no structures along the path capable of indicating an EF5 rating. Obviously, any tornado that causes genuine EF5 damage is going to do it in a small area relative to the rest of the path, which makes sense. Still, the ASCE's logic is not a good way to approach tornado damage surveying, especially since most structures in the US are poorly built and surveying taking only engineering into consideration sets an impossibly high bar for EF5 ratings.

 

[andyhb]

Neither were as clear cut as Moore, both Chapman and Vilonia were 100% EF-5 strength, but neither have as reliable EF-5 dis.

Well Vilonia did, they just went to silly lengths to discount them. Oh, and they also didn't survey probably a couple dozen EF5 candidates.

 

[UK_EF4]

Neither were as clear cut as Moore, both Chapman and Vilonia were 100% EF-5 strength, but neither have as reliable EF-5 dis.

I don't know too much about Chapman, but I can fairly confidently say that Vilonia had *at least* 1 EF5 DI backed up by high end contextual damage throughout parts of the tornado's path. That home was very well connected, and the main reasons that DI was not given EF5 were: "Ratings are not normally assigned based on one only structure", homes were impacted from debris in the downtown, and trees standing 100ft away. If the second and third reasons were applied to Moore, it wouldnt be rated EF5. The first reason is just straight up incorrect surveying. That's about as clear cut as you can get for a home, in my opinion - and there were many other marginal candidates too.

 

[jiharris0220]

If engineers used the same logic that went into the vilonia survey or NWS Lubbock’s surveys than there wouldn’t be a single tornado I can think of that would get ef5 today, with perhaps the exception being ironically the non conventional oil rig DI in Piedmont.

 

[pohnpei]

Just for the sake of curiosity, can anyone think of any tornadoes that did extreme damage in a town but relatively little outside of it?

I actually would name Joplin. Joplin touched down right near the city, quickly strengthening into EF5 intensity and maintained violent intensity throughout the city.

Joplin, MO Tornado Response Imagery

You can from this that it almost immediately weakened after it left the city. It could be still at EF2 intensity after Joplin but it's a far cry from what it capable of in the city.

Another suitable case was San Justo which was a very short track tornado that give all its power inside the town.

 

[HAwkmoon]

The house in Vilonia that had both its exterior and interior walls bolted down, and the well constructed homes in Chapman (one of which was swept away with such force that a part of its poured concrete foundation was snapped, and another that basically disappeared with no debris remaining) seem like pretty reliable EF5 DI's to me.


Even taking the small sample size into consideration, the point of that study was still this: from a 'pure' engineering perspective, there were very few to no structures along the path capable of indicating an EF5 rating. Obviously, any tornado that causes genuine EF5 damage is going to do it in a small area relative to the rest of the path, which makes sense. Still, the ASCE's logic is not a good way to approach tornado damage surveying, especially since most structures in the US are poorly built and surveying taking only engineering into consideration sets an impossibly high bar for EF5 ratings.

I and someone studying forensic engineering looked at that home, that home quoting the DAT here as well "straight nail wall studs had unknown reinforcement" therefore there was a lack of confidence, plus some of the bolts lacked nuts and washers looking at upscaled images. The trees a metre away being hardly debarked is another detail that holds it back. There were other houses not surveyed though which probably were EF-5.

As for Chapman, that home had nuts and washers, but they were very badly rusted and failed, so EF-4 again makes sense.

 

[Sawmaster]

Then I have to go back to my prior objections - what's the point of defining EF5 so that it can only by hitting a house build to a standard only 0.05% in the tornado-prone area actually achieve? It's not a secret that seismic or hurricane resistant construction are rare outside of areas zoned for that.

I'd also add that the ASCE - managed plenty of objections to hurricane resistant housing in the 2022 Arabi tornado.

I created a detailed response here, but it's length and subject matter are more appropriate for the "Enhanced Fujita Ratings Debate" forum so I posted it there instead. You can find it HERE

For those who won't go there it shows a different perspective of what the report mentioned in the OP does, and I explain why. I feel that any further discussion of this specific matter belongs there, so as to not disrupt the subject matter this forum seems to be made for.

 

[jiharris0220]

I and someone studying forensic engineering looked at that home, that home quoting the DAT here as well "straight nail wall studs had unknown reinforcement" therefore there was a lack of confidence, plus some of the bolts lacked nuts and washers looking at upscaled images. The trees a metre away being hardly debarked is another detail that holds it back. There were other houses not surveyed though which probably were EF-5.

As for Chapman, that home had nuts and washers, but they were very badly rusted and failed, so EF-4 again makes sense. View attachment 28658

Engineers like you and others around the country that survey tornado damage are the best in the business and know full and well what you’re doing.

With that being said, I think this post is a clear cut example of why engineers are playing a big role in under rating tornadoes. Not saying you guys are underestimating tornadoes, but rather under rating them.

It goes back to the saying “we’re looking too much into how strong was this structure rather than how strong was this tornado?”

There needs to be a balance between the two criteria in order to avoid things like this.

 

[Juliett Bravo Kilo]

Engineers like you and others around the country that survey tornado damage are the best in the business and know full and well what you’re doing.

With that being said, I think this post is a clear cut example of why engineers are playing a big role in under rating tornadoes. Not saying you guys are underestimating tornadoes, but rather under rating them.

It goes back to the saying “we’re looking too much into how strong was this structure rather than how strong was this tornado?”

Yup, being an engineer does not make one a meteorologist.

 

[Sawmaster]

I and someone studying forensic engineering looked at that home, that home quoting the DAT here as well "straight nail wall studs had unknown reinforcement" therefore there was a lack of confidence, plus some of the bolts lacked nuts and washers looking at upscaled images. The trees a metre away being hardly debarked is another detail that holds it back. There were other houses not surveyed though which probably were EF-5.

As for Chapman, that home had nuts and washers, but they were very badly rusted and failed, so EF-4 again makes sense. View attachment 28658

Rusty or not, the fasteners in this picture are still intact and with the two seen both being at the same height of containment, it is very unlikely that they failed in any structural way even if they appear rusty. Surveying will usually result in an incorrect conclusion when you fail to consider what you can clearly see versus focusing on only what is on a checklist, and once again we see a definite bias against issuing a realistic rating based on a tunnel-visioned approach.

 

[jiharris0220]

Rusty or not, the fasteners in this picture are still intact and with the two seen both being at the same height of containment, it is very unlikely that they failed in any structural way even if they appear rusty. Surveying will usually result in an incorrect conclusion when you fail to consider what you can clearly see versus focusing on only what is on a checklist, and once again we see a definite bias against issuing a realistic rating based on a tunnel-visioned approach.

The EF scale wasn’t intended to be used with strict nitpickey engineering standards, which is why it’s fails spectacularly so often. And why there are planetary differences between offices in rating methodologies, because some engineers are more strict than others regarding damage criteria.

I mean, those rusty bolts definitely did contribute to that structure failing, but that’s the thing. It shouldn’t matter, anchor bolts/fasteners plus clean slab and of course adequate contextual damage should equal ef5 period.

 

[TH2002]

**

I and someone studying forensic engineering looked at that home, that home quoting the DAT here as well "straight nail wall studs had unknown reinforcement" therefore there was a lack of confidence, plus some of the bolts lacked nuts and washers looking at upscaled images. The trees a metre away being hardly debarked is another detail that holds it back. There were other houses not surveyed though which probably were EF-5.

As for Chapman, that home had nuts and washers, but they were very badly rusted and failed, so EF-4 again makes sense. View attachment 28658

I do not follow your logic. The reason the Vilonia home had unknown reinforcement is because NWS Little Rock didn't bother to look into it further, which most definitely says nothing about the home's structural integrity. Expecting every tree in the vicinity of a destroyed home to be fully debarked also goes against what we know about multiple vortices.

I could also use either the "straight nailed studs" and/or "rusty bolts and washers" excuse to nitpick literally every EF5 rated home in Moore to EF4, as well as the Oak Grove home in Hackleburg.