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Dec. 10-11 Severe Weather


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Like many of you, I am confused by Tim’s statement. Our benchmark for ef5 now is one tornado measured at over 300mph, and another tornado that imparted f5 impacts on a given location for longer than practically any other on record?

If that’s the case, why would we even consider 201 mph the threshold, and not  something higher like 250 or 300?

 

edit:typo

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14 hours ago, DanLarsen34 said:

Let’s remember, this survey is currently preliminary. That means further inspection and discussion could lead to an EF-5 rating. 
 

That said, if this doesn’t end up there in the coming weeks, I agree with the sentiment that has been expressed in this thread. Basically, there’s almost no areas out there that have structures built up to the standard that would enable an EF-5 rating, and contextual evidence beyond that is just not seen as reliable enough to give a rating beyond that, even if it should be IMHO.

Yall may remember the Rainsville tornado on 27 April 2011. The Huntsville NWS had originally given it a high EF4 rating & the video I shared from Jim's Bham NWS that Superoutbreak still shows that. But after further research Hville NWS bumped it up to a "low end" EF5, giving it a max wind speed of > 200 mph, not even 205, just barely over 200. 

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Hm. Well, it's splitting hairs to some degree I think (10mph from EF-5); very similar overall "thinking" to Bassfield, which as many recall we all were discussing an EF-5 rating as well. 

I actually have a counter-thought with respect to Tim Marshall. What if he gets called in when the NWS team *doesn't* have the damage indicators it needs to make its own assessment and needs an outside expert to review things that have been destroyed and basically assign a damage indicator rating on the fly? Many have pointed out that the structures on path wouldn't be able to generate an EF-5 rating. My interpretation when they called in the "experts" was that, they had damage that they were struggling to classify. Otherwise, why bring in said experts? Yes high ratings are important publicly speaking--but they're the sole discretion of the office in the affected CWA.

I also wonder, would those 2011 ratings have changed? Or, were there genuinely different building materials or other factors? I feel like, as much as we are kind of trashing tim (et al) right now, he obviously *is* an expert on tornado intensity. I'd be curious to understand the process Tim himself goes through when he does these evals. Does he incorporate Doppler radar data concurrent to the location he's evaluating? How does he and the NWS evaluate something that is "beyond destroyed"? What I mean is, I picture Tim coming in to answer the question, "this well built home was slabbed but xyz was not built correctly so there's XYZ ambiguity, is there anything you can see in the wreckage that looks like it would take a higher wind speed to be able to do THAT destruction?". One thing I've read about EF-5 damage is that the debris is often "pulverized" into a "fine powder" with "little recognizable from the original structure". Of course if that is the bar, there are EF-5s and F5s that would under our current rating scheme get downgraded.

All this said, my gut instinct is, hard as it is to believe, had Tim and co found some type of incredible damage as it were, they could still have issued an EF-5 rating on path. That's why they call in the experts. Arguably, we probably rated tornadoes overly agressive in the past, as opposed to rating them too-low now. Various numerics during the tornado including vrot had many on Twitter and a couple on here calling it EF-4 strength (while noting, if it were a bit closer to higher STPs and more population it'd be a 5). But since it wasn't, technically the radar does kinda track with a very high end 4 ( 30k feet debris loft is significant though--but could also be a function of the strength of the overall supercell's organization, which makes sense for many reasons and is what enabled such a strong tornado in the first place).

 

My final thought is, based on all the above, this would've been a 5 in 2011, 2007, before the EF scale (etc). The reason it isn't now feels like it is less to do with a change in *damage*, instead, we have a much better understanding of what *wind speed* is required to *produce* given damage (and for what duration and at what angle that wind must impinge on the structure or object in question). We understand now that things like forward speed, and angle of approach, can influence damage to structures. Therefore, I'd argue that the *windspeed* estimate is probably right, and the scale itself might need to be tweaked. We all know, EF5 means "incredible" and "catastrophic" damage. This IS that damage. It is just that. Catastrophic. And not to split hairs but it's more than "Devastating". I'd argue, devastating means everything is destroyed but it doesn't look like entire towns were model cities that had been carelessly thrown off the end of a high table by a child. Particularly what I saw coming out of Bremen. 

I therefore suggest we reconsider our rating criteria, by reducing the wind speed threshold required for EF5 ratings. The point of the rating is to inform the severity. This is top tier severity, it should have a top tier rating. If 190 mph winds do this damage, 190 should be a 5. 

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48 minutes ago, Moderately Unstable said:

Hm. Well, it's splitting hairs to some degree I think (10mph from EF-5); very similar overall "thinking" to Bassfield, which as many recall we all were discussing an EF-5 rating as well. 

I actually have a counter-thought with respect to Tim Marshall. What if he gets called in when the NWS team *doesn't* have the damage indicators it needs to make its own assessment and needs an outside expert to review things that have been destroyed and basically assign a damage indicator rating on the fly? Many have pointed out that the structures on path wouldn't be able to generate an EF-5 rating. My interpretation when they called in the "experts" was that, they had damage that they were struggling to classify. Otherwise, why bring in said experts? Yes high ratings are important publicly speaking--but they're the sole discretion of the office in the affected CWA.

I also wonder, would those 2011 ratings have changed? Or, were there genuinely different building materials or other factors? I feel like, as much as we are kind of trashing tim (et al) right now, he obviously *is* an expert on tornado intensity. I'd be curious to understand the process Tim himself goes through when he does these evals. Does he incorporate Doppler radar data concurrent to the location he's evaluating? How does he and the NWS evaluate something that is "beyond destroyed"? What I mean is, I picture Tim coming in to answer the question, "this well built home was slabbed but xyz was not built correctly so there's XYZ ambiguity, is there anything you can see in the wreckage that looks like it would take a higher wind speed to be able to do THAT destruction?". One thing I've read about EF-5 damage is that the debris is often "pulverized" into a "fine powder" with "little recognizable from the original structure". Of course if that is the bar, there are EF-5s and F5s that would under our current rating scheme get downgraded.

All this said, my gut instinct is, hard as it is to believe, had Tim and co found some type of incredible damage as it were, they could still have issued an EF-5 rating on path. That's why they call in the experts. Arguably, we probably rated tornadoes overly agressive in the past, as opposed to rating them too-low now. Various numerics during the tornado including vrot had many on Twitter and a couple on here calling it EF-4 strength (while noting, if it were a bit closer to higher STPs and more population it'd be a 5). But since it wasn't, technically the radar does kinda track with a very high end 4 ( 30k feet debris loft is significant though--but could also be a function of the strength of the overall supercell's organization, which makes sense for many reasons and is what enabled such a strong tornado in the first place).

 

My final thought is, based on all the above, this would've been a 5 in 2011, 2007, before the EF scale (etc). The reason it isn't now feels like it is less to do with a change in *damage*, instead, we have a much better understanding of what *wind speed* is required to *produce* given damage (and for what duration and at what angle that wind must impinge on the structure or object in question). We understand now that things like forward speed, and angle of approach, can influence damage to structures. Therefore, I'd argue that the *windspeed* estimate is probably right, and the scale itself might need to be tweaked. We all know, EF5 means "incredible" and "catastrophic" damage. This IS that damage. It is just that. Catastrophic. And not to split hairs but it's more than "Devastating". I'd argue, devastating means everything is destroyed but it doesn't look like entire towns were model cities that had been carelessly thrown off the end of a high table by a child. Particularly what I saw coming out of Bremen. 

I therefore suggest we reconsider our rating criteria, by reducing the wind speed threshold required for EF5 ratings. The point of the rating is to inform the severity. This is top tier severity, it should have a top tier rating. If 190 mph winds do this damage, 190 should be a 5. 

Obviously you’re the met, so your opinion is much better informed than mine, but it seems to me that if if our intensity scale is to continue relying heavily on damage produced over other indicators, that the scale needs to be updated with more non-urban damage indicators for EF4+ tornadoes, rather than a downward adjustment of winds in the ef5 category. In concept, it doesn’t make a whole lot of sense that a tornado’s intensity is only as strong as the building it hits (or doesn’t hit) but even with improvements in technology, it’s still the best we’ve got. Tornadoes predominantly hit rural or even unpopulated areas, and if tornado intensity is going to continue to be evaluated by this methodology, I would think the next logical step in improving the scale would be to accommodate that fact better.
 

The NIST slideshow about Joplin that was posted above makes note of the large amount of subjectivity that comes into play when evaluating unconventional damage indicators due to construction methods that can’t generate an ef5 rating. I’m sure Tim’s statement was made on the fly, but using two tornadoes that were clearly well above the F5 threshold as the benchmark for 201mph winds doesn’t seem like a fair comparison to me.

 

If I had any say in the matter, I personally would only advocate for lowering the wind threshold if structural engineering studies determined that what is generally considered ef5 damage was produced at lower wind speeds, or if we were to lower the standard for what is considered ef5 damage. 
 

Let me know if my line of thinking here isn’t correct.

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1 hour ago, Chreeyiss said:

Obviously you’re the met, so your opinion is much better informed than mine, but it seems to me that if if our intensity scale is to continue relying heavily on damage produced over other indicators, that the scale needs to be updated with more non-urban damage indicators for EF4+ tornadoes, rather than a downward adjustment of winds in the ef5 category. In concept, it doesn’t make a whole lot of sense that a tornado’s intensity is only as strong as the building it hits (or doesn’t hit) but even with improvements in technology, it’s still the best we’ve got. Tornadoes predominantly hit rural or even unpopulated areas, and if tornado intensity is going to continue to be evaluated by this methodology, I would think the next logical step in improving the scale would be to accommodate that fact better.
 

The NIST slideshow about Joplin that was posted above makes note of the large amount of subjectivity that comes into play when evaluating unconventional damage indicators due to construction methods that can’t generate an ef5 rating. I’m sure Tim’s statement was made on the fly, but using two tornadoes that were clearly well above the F5 threshold as the benchmark for 201mph winds doesn’t seem like a fair comparison to me.

 

If I had any say in the matter, I personally would only advocate for lowering the wind threshold if structural engineering studies determined that what is generally considered ef5 damage was produced at lower wind speeds, or if we were to lower the standard for what is considered ef5 damage. 
 

Let me know if my line of thinking here isn’t correct.

Nope, we're on the same page. We need to have a 3rd revision to the EF scale. Specifically we need to be able to come up with valid damage indicators for, as you note, rural areas. One of the main concepts of the EF scale when it was introduced was that it was supposed to retain continuity with the old rating system. E.g. the numerical wind speed estimates were going to change, but, the same type of damage on the F scale was intended to be rated the same on the EF scale...just with more accurate wind estimates and more specific damage indicators. That isn't currently happening imho. An F5 of old does not seem to be an EF5 now. I do think there's some merit to the chatter going around about the rating still being preliminary (other 190 mph tornadoes have indeed been upgraded to 200...it really is a tiny difference). However, if they don't upgrade, I hope they produce a very detailed report (I'm sure they will), that explains all of the factors that got them to their conclusion. And I hope that report doesn't say "we thought there could be EF-5 damage, but, couldn't find damage indicators to support it". Conversely, if they say, "radar estimates along with contemporary research into tornado intensities as related to debris height, vrot, wind tunnel testing and other physical studies, suggest this tornado was demonstrably weaker than EF5s on record because of A, B, C", I would be ok with that. At the moment though, since the damage rating is preliminary, it may yet get upgraded. Either way....we need a better way to rate rural tornadoes. There should also be some type of discussion amongst the research community at this juncture as to whether our radar measurements have grown accurate enough to be allowed to "factor in" to the rating. Take El Reno. We know it was a 5, by 100 mph. Because DOWs measured that. But it's a 3 due to the damage indicator problem. That in my view becomes an actual research problem. If I'm were to do a tornado study, and I am pulling up atmospheric conditions present for "F5" tornadoes, trying to draw conclusions...my conclusions will be flawed if the ratings depend on the type of structures being impacted. Meteorologically, the atmosphere does not care if there's a city or a field below it. But the rating system does, which would lead to biased results (potentially). At the least, it gives researchers an incorrect sample population and incorrectly classifies the rarity or lack thereof of specific tornadic intensities. Our current scale "favors" EF3s and EF4s, when we're talking major damage, and that's solely due to the design of the damage indicator system. I'm not saying every high end EF4 should be a 5, but this is the latest of several tornadoes that really hint at top end damage, and aren't getting that top end rating. 

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19 hours ago, brianc33710 said:

Would these "underratings" relate to insurance companies and/or aid groups that dole out more aid for 5s than 4s & dont want to give out more money? Im being serious, not a smart ass.....just want to make sure this comment isnt read the wrong way.

I think you have a misunderstanding of how insurance companies provide compensation for natural disasters. It’s based off the cost of insured losses, not EF rating.

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26 minutes ago, Cartier God said:

I think you have a misunderstanding of how insurance companies provide compensation for natural disasters. It’s based off the cost of insured losses, not EF rating.

This was just a WAG trying to figure out why they seem so reluctant to rate tornadoes an EF5. Most members here, many of them meteorologists, find the damage on par with 27 April 2011s EF5s. Even then though there were EF4s that many experts believed should be EF5s & at least a couple EF3s that some argue were EF4s. As I said, a WAG.....thats all. 

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15 minutes ago, brianc33710 said:

This was just a WAG trying to figure out why they seem so reluctant to rate tornadoes an EF5. Most members here, many of them meteorologists, find the damage on par with 27 April 2011s EF5s. Even then though there were EF4s that many experts believed should be EF5s & at least a couple EF3s that some argue were EF4s. As I said, a WAG.....thats all. 

What does WAG mean

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1 minute ago, brianc33710 said:

Wild Ass Guess

Oh okay. I was just explaining why it was wrong. I’ve seen a couple weenies online push this conspiracy and its complete bs. The ratings for this outbreak were egregious but acting like its some scheme for WFOs to deny people who lost their homes financial aid is ridiculous.

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Even the fact that a preliminary analysis of this turns out an EF-4 designation is very problematic.  There are several obvious indicators that this was as strong as other tornadoes that have been given both the EF-5 and F-5 designation.  Stating that there is a lack of "well-built" structures that have been swept away with only slabs remaining as a justification of not finding EF-5 damage is absurd.  As an architect this frustrates me because how is anybody defining what "well-built" means, and more importantly:  How can you determine if something was well-built if the entire damn structure is gone?  People can say "Well look at the anchorage".  There is no building code that requires a structure have anchorage that can survive 200 mph winds.  From an engineering standpoint is isn't feasible with wood frame buildings (never mind the fact that the 200 MPH winds are throwing cars, trucks, etc at high velocities that impact the structure).  

I cannot emphasize this enough:  A building is only as "well-built" as the local building codes dictate.  The definition of "well-built" should not be determined by the ability to partially survive a 200 MPH tornado.  Building codes do change often times, and are usually caused by natural disasters.  However I can pretty much guarantee that building codes in tornado alley do not have provisions like those in other natural disaster afflicted areas (hurricane zones, seismic zones, etc).  And even if they have it is a moot point because the damage assessment requirements are extremely vague.

The EF scale is so flawed on so many levels that its hard to even use it as a scientific tool.  How can the El Reno tornado be an EF-3 when 300 mph winds were measured by DOW? How can the Jarrell tornado be an EF-5 based on damage alone when it was moving 10 mph (as opposed to other faster moving EF-5's like this one who did the same damage)?  How are we simply ignoring other factors like defoliation, trees being debarked, ground scouring, etc? 

Damage should never be the be all, end all factor in determining tornadic windspeeds:  because we have no earthly idea why tornadic windspeeds do the damage they do.  And I present the picture below as evidence.  Nobody who is assessing damage can sit in front of me and tell me with a straight face that this tornado did not have 200 mph winds because of poorly built structures when we have a damn bookshelf with books untouched while the entire rest of the house is completely gone.  Its all completely absurd and incredibly unscientific. 

c2e6eb49f170e7736759cc3cad509735.webp.50bad17771474fb1eebca2b9509a7ef0.webp

 

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Some good points have been made throughout.  Ultimately, the EF scale is a damage scale, and it's what we have right now.  As mentioned previously, I would like to see an expansion to include more damage indicators as it would help remove some of the biases that currently exist with the scale.  I'm not sure how feasible it is to include things like crops and trenches dug by a tornado though.  Trees are part of the damage indicators and they grow out of the ground like crops do, so maybe something can be done with that lol

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Tornadoes need a NESIS or ACE like scale that would account for not just the amount of damage but the areal coverage of the damage. 

I don't mean any disrespect to the Ashby/Dalton, MN EF-4 it was an awesome tornado that I would have loved to catch if I was storm chasing. However, it really doesn't belong in the same class as something with a 170 mile path length that was a mile wide.

https://www.weather.gov/fgf/2020_07_08_Tornadoes

https://www.weather.gov/pah/December-10th-11th-2021-Tornado

 

 

 

 

 

 

 

 

 

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NWS Memphis is posting surveys and while awaiting visuals, I plucked this from their latest PIS put out about an hour ago. The long-track supercell was two separate tornadoes, officially. 170mph EF-4 with a path of 80.3 miles and an incredible max width of 1,800 yards.

Quote

THE TORNADO'S WIDTH WAS SHRINKING AS IT APPROACHED SAMBURG, HOWEVER,   IT WAS STILL STRONG ENOUGH TO DAMAGE HOMES, BUSINESSES, AND CITY   BUILDINGS IN SAMBURG. MANY HOMES SUFFERED PARTIAL ROOF LOSS, AND   SEVERAL MOBILE HOMES WERE SEPARATED FROM THEIR UNDERCARRIAGES. THE   TORNADO CONTINUED NORTHEAST FROM SAMBURG, DAMAGING SEVERAL HOMES   ALONG OLD SAMBURG ROAD. THE LAST OBSERVED DAMAGE WAS WEST OF TREECE   ROAD.

 

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23 minutes ago, SmokeEater said:

Actually not EF4 now, somebody behind the scenes messed up. NWS Louisville themselves are actually calling people out on social media who shared it, saying it's false information.

Sent from my SM-G973U using Tapatalk
 

They’re being low-key condescending towards people questioning this too, and I completely understand why their decision is being scrutinized. No explanation from them as to why they’d go so low with what appears to be EF4-worthy damage. “Because 165 is what we estimated, and because we said so” is not sufficient explanation. Totally dismissive and ridiculous.

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Tornadoes need a NESIS or ACE like scale that would account for not just the amount of damage but the areal coverage of the damage. 
I don't mean any disrespect to the Ashby/Dalton, MN EF-4 it was an awesome tornado that I would have loved to catch if I was storm chasing. However, it really doesn't belong in the same class as something with a 170 mile path length that was a mile wide.
https://www.weather.gov/fgf/2020_07_08_Tornadoes
https://www.weather.gov/pah/December-10th-11th-2021-Tornado
 
 
 
 
 
 
 
 
 

I’ve always thought this as well. Like the St. Louis airport E-4 a few years back, there’s no comparison between a tornado that does E-4 damage at a single location vs one that does so over dozens of miles. That’s why I’ve usually considered Hackleberg one of the most impressive tornadoes since I followed this stuff. Devastating damage over incredible distance. Regardless of what rating the W. Kentucky tornado gets, it’s the sheer scale of the damage over so many miles that puts this one in a unique group.


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1 minute ago, andyhb said:

I know, I just posted that for the receipts

Also they apparently rated this EF2? Huh?

That’s the one damage point that has me the most baffled. You literally have to go below the lower bound wind speed (aka break the rules and guidelines of the scale) to assign such a low rating to a slabbed residential structure, and one that is clearly anchor bolted none the less. Would love to hear an actual explanation from them, but I doubt we’ll get one. 

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That’s the one damage point that has me the most baffled. You literally have to go below the lower bound wind speed (aka break the rules and guidelines of the scale) to assign such a low rating to a slabbed residential structure, and one that is clearly anchor bolted none the less. Would love to hear an actual explanation from them, but I doubt we’ll get one. 




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Just now, Chicago Storm said:

 

 

 


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More nonsense.  That is a standard wood stud framed single family home with brick veneer facing.  It has standard anchorage to the slab as seen by the bolts sticking out of the base stud.  The brick is completely non-structural and can actually be removed by winds lower than 100 mph.  The wood framed building cannot be removed by winds that low, and that is fairly obvious.  They have no clue what they are looking at if they think an EF-2 tornado did that.

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5 minutes ago, Normandy said:

More nonsense.  That is a standard wood stud framed single family home with brick veneer facing.  It has standard anchorage to the slab as seen by the bolts sticking out of the base stud.  The brick is completely non-structural and can actually be removed by winds lower than 100 mph.  The wood framed building cannot be removed by winds that low, and that is fairly obvious.  They have no clue what they are looking at if they think an EF-2 tornado did that.

I am beginning to suspect that WFOs are outsourcing much of their survey work to engineering firms with no meteorological background or any awareness about how contextual evidence works, or any understanding of the different hallmarks of the varying degrees of tornado intensity levels. If this is true, we have a serious problem, and a better understanding of why underrated tornadoes have become the norm. 

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