4/27/2011 Pleasant Grove, AL damage

[JRC]

Good afternoon everyone. First time posting.

Like many of you I am fascinated by weather, particularly severe weather (severe thunderstorms, derechos, tornadoes, microbursts, etc). Growing up in AL, I mean how could you not be. I tell my wife (who grew up in GA) that in Alabama there are 2 things everyone from Carrollton, AL to Oxford, AL to Hunstville, AL, to Mobile, AL have in common: 1) college football love 2) eye for severe weather.

Like you all I have viewed hundreds of images of the cell that began southwest of Tuscaloosa, AL and ended in northwest GA. The damage in Concord,AL and Pleasant Grove, AL has often elicited the question, "how is that damage not consistent with EF5?". Trees (hardwood and softwood) debarked, structures displaced from foundation, etc. I remember driving through Pleasant Grove about a month after the tornado and the landscape had permanently changed.

I am hoping to get some feedback from you all on two fronts:
1. In today's world it appears everything can become political, even weather. Is it possible the reason the EF5 designation was not given was due to reasons outside of the event itself?
2. In comparing pictures from Moore, OK, Joplin, MO, Pleasant Grove, AL, etc. I see very similar if not exact damage markers. In reference to EF5 designation, what should I be looking for in the pictures that the National Weather Service saw on the ground, that I am not observing?

Thanks everyone

Justin

 

[buckeye05]

Good afternoon everyone. First time posting.

Like many of you I am fascinated by weather, particularly severe weather (severe thunderstorms, derechos, tornadoes, microbursts, etc). Growing up in AL, I mean how could you not be. I tell my wife (who grew up in GA) that in Alabama there are 2 things everyone from Carrollton, AL to Oxford, AL to Hunstville, AL, to Mobile, AL have in common: 1) college football love 2) eye for severe weather.

Like you all I have viewed hundreds of images of the cell that began southwest of Tuscaloosa, AL and ended in northwest GA. The damage in Concord,AL and Pleasant Grove, AL has often elicited the question, "how is that damage not consistent with EF5?". Trees (hardwood and softwood) debarked, structures displaced from foundation, etc. I remember driving through Pleasant Grove about a month after the tornado and the landscape had permanently changed.

I am hoping to get some feedback from you all on two fronts:
1. In today's world it appears everything can become political, even weather. Is it possible the reason the EF5 designation was not given was due to reasons outside of the event itself?
2. In comparing pictures from Moore, OK, Joplin, MO, Pleasant Grove, AL, etc. I see very similar if not exact damage markers. In reference to EF5 designation, what should I be looking for in the pictures that the National Weather Service saw on the ground, that I am not observing?

Thanks everyone

Justin

It's all about construction and context. The homes in Pleasant Grove were generally built unanchored on cinder block construction foundations. That kind of construction will not allow for a rating above EF4. Yes trees were debarked, but the highest that tree damage can be rated on the scale is low EF4. Also, surveyors noted that vehicles from many homes in Pleasant Grove were displaced, but not thrown incredible distances. All in all, that is in no way shape or form EF5, even if it looks visually impressive. Any violent tornado is going to produce widespread destruction that looks "Joplin-ish" if it impacts a densely populated residential or urban area.

 

[JRC]

It's all about construction and context. The homes in Pleasant Grove were generally built unanchored on cinder block construction foundations. That kind of construction will not allow for a rating above EF4. Yes trees were debarked, but the highest that tree damage can be rated on the scale is low EF4. Also, surveyors noted that vehicles from many homes in Pleasant Grove were displaced, but not thrown incredible distances. All in all, that is in no way shape or form EF5, even if it looks visually impressive. Any violent tornado is going to produce widespread destruction that looks "Joplin-ish" if it impacts a densely populated residential or urban area.

I appreciate the reply and the feedback. I did further reading on the 28 indicators of establishing an EF status to a tornado. When reviewing the upper bound and lower bound graphs, I did see several markers for an EF5 (especially in Tuscaloosa City, Concord, and Pleasant Grove). The areas of Concord and Pleasant Grove, which I personally visited less than a month after the storm , did show several of the UB markers on the 28 indicators. Majority of homes (with basements) were removed from the foundation of the basement, hardwood/softwood trees debarked and uprooted or snapped in half, and vehicles/boats tossed several hundred yards. The homes built in the areas of Pleasant Grove and Concord that I visited were homes valued within the $200,000 to $250,000 range and were mostly 4-sided brick with concrete basements.

I can see the points noted previously by buckeye05 however it is questionable as to whether the storm was not an EF5. I know in the grand scheme of things, it does not matter to those directly affected by the storm.

Thanks for the feedback

Justin

 

[buckeye05]

I appreciate the reply and the feedback. I did further reading on the 28 indicators of establishing an EF status to a tornado. When reviewing the upper bound and lower bound graphs, I did see several markers for an EF5 (especially in Tuscaloosa City, Concord, and Pleasant Grove). The areas of Concord and Pleasant Grove, which I personally visited less than a month after the storm , did show several of the UB markers on the 28 indicators. Majority of homes (with basements) were removed from the foundation of the basement, hardwood/softwood trees debarked and uprooted or snapped in half, and vehicles/boats tossed several hundred yards. The homes built in the areas of Pleasant Grove and Concord that I visited were homes valued within the $200,000 to $250,000 range and were mostly 4-sided brick with concrete basements.

I can see the points noted previously by buckeye05 however it is questionable as to whether the storm was not an EF5. I know in the grand scheme of things, it does not matter to those directly affected by the storm.

Thanks for the feedback

Justin

You're definitely on the right track here, but high quality construction is absolutely necessary for an EF5 rating to even be considered. This was not present in any way shape or form in Pleasant Grove or Concord. Having a "concrete basement" doesn't have anything to do with the quality of construction. In this case, it was quite the opposite. I have seen the pictures of the homes mentioned above, and the type of basement they were built on utilized cinder block construction. This prevents there from being a continuous load like there would be with a poured concrete stem wall basement foundation with proper anchor bolts. These cinder blocks will shift as wind puts stress on the house. The house shifts, the cinder blocks fall and crumble, and the whole house goes with it. The worst part about this kind of foundation is that the house itself is usually not even attached to the foundation at all, and is simply sitting there via gravity alone or a few nails in the best case scenario. This picture from Pleasant Grove is a perfect example:

You can see where the unstable cinder block foundation failed and crumbled, causing the entire wooden floor platform slide off of the foundation and taking the whole house with it. This is what tornado damage surveyors call a "slider" and it usually isn't rated above EF3 unless overall context undoubtedly suggests a violent tornado (such as this case). "Sliders" are the result of very poor quality construction, and thus a rating above EF4 was not possible in Concord or Pleasant Grove. When an EF5 rating is being considered, a home absolutely must be built on a strong poured concrete slab or basement foundation with extensive anchor-bolting of the walls to the foundation. Homes of this type were not present along the Tuscaloosa/Birmingham tornado path, though they were at multiple points along the Smithville, Rainsville, and Hackleburg tornado paths, thus the difference in ratings. Hope this clears up how the scale and rating process works somewhat for you! It's very fascinating stuff.

 

[JRC]

It really does seem to come down to semantics ("EF 5 or EF 4"). The National Weather Service survey team had a preliminary identification of EF 4 at 4:00pm on May 23, 2011 (1 day after the storm) and then changed the identification later based on additional data. I am curious as to what data changed the identification.

I am sure everyone has an opinion on how EF status is assigned especially those who live in or around places like Joplin or Tuscaloosa.

Lastly, the report submitted in June 2013 by the American Society of Civil Engineers is very interesting as it found no evidence of EF5 damage (which I am not sure I agree with).

I am not an expert but I do have an opinion and isn't "right or wrong". Given the EF status is based on a premise of a 3-second wind speed, I would have to disagree with both the NWS and the ASOCE. Based on everything I have personally observed and read, both storms consisted of a period of time existed where wind gusts exceeded 200mph. Looking at the images below and not knowing which represents which city (Joplin, Tuscaloosa, Pleasant Grove, Concord) it really is hard to tease out 199mph and 201mph.

 

[ARCC]

Severe damage for sure, but personally I do not see any evidence of EF5 damage in any of the images, possibly not even high end EF4 damage.

 

[buckeye05]

It really does seem to come down to semantics ("EF 5 or EF 4"). The National Weather Service survey team had a preliminary identification of EF 4 at 4:00pm on May 23, 2011 (1 day after the storm) and then changed the identification later based on additional data. I am curious as to what data changed the identification.

I am sure everyone has an opinion on how EF status is assigned especially those who live in or around places like Joplin or Tuscaloosa.

Lastly, the report submitted in June 2013 by the American Society of Civil Engineers is very interesting as it found no evidence of EF5 damage (which I am not sure I agree with).

I am not an expert but I do have an opinion and isn't "right or wrong". Given the EF status is based on a premise of a 3-second wind speed, I would have to disagree with both the NWS and the ASOCE. Based on everything I have personally observed and read, both storms consisted of a period of time existed where wind gusts exceeded 200mph. Looking at the images below and not knowing which represents which city (Joplin, Tuscaloosa, Pleasant Grove, Concord) it really is hard to tease out 199mph and 201mph.
View attachment 319 View attachment 320 View attachment 321 View attachment 322 View attachment 323 View attachment 324

It isn't semantics, and I just gave you a thorough explanation about how structural integrity is a huge part of the final rating. Also, none of the structures in those photos you have posted have been swept clean, and as ARCC said, that isn't indicative of anything beyond maybe low EF4. Saying "this widespread destruction is indistinguishable from Joplin or Moore" or wherever is not how the EF scale works. It is done on a structure by structure basis, and the structures in Concord and Pleasant Grove were not well-built, making an EF5 rating out of question. And as I said, any high-end EF3 or stronger is going to produce damage that looks like the above photos if a densely populated area is impacted. End of story. I'd do a little more research on what actually defines EF5 damage and how the scale is applied before making such bold assertions that the NWS is wrong. It isn't really an "opinion" based topic; it comes down to understanding how the scale is applied.

 

[JRC]

Let me start by saying, the images I posted are of Joplin, MO, Tuscaloosa, AL, and Pleasant Grove, AL. My point in doing so is an attempt to show the details (without context of location) of structure damage, landscape damage,etc. and how details can easily be overlooked in the face of such devastation.

Next, I am not sure how someone could be offended with the images above being labeled EF4 or EF5. My initial post was to get feedback on other people's interpretations of the EF5 classification decision.

Of the 28 markers, only one has been critiqued on this thread. The quality of construction of homes built in Joplin versus quality of hose built in Pleasant Grove. Broad statements describing "all" of the structures in a particular city do little to further the conversation. Unless the NWS survey team observed and evaluated every single structure (or what was left of it) along this line:

then it stands to reason there is a possibility they missed something. Hence the 199mph vs. 201mph point.

Lastly, if my posts were read, it is clear no assertion that NWS was "wrong" has been stated. Distinguishing between EF4 and EF5 is a judgement call. I disagree with their judgement. Period.

 

[Evan]

Prior to the tornado, I had been in the basements of well over a dozen (more like two dozen plus) of the homes that were destroyed. Some of the homes destroyed are homes that I spent considerable time in as a child, pre-teen, and as a teenager.

I know for a fact that the quality of construction varies considerably -- you had at least 6-12 if not more homebuilders that constructed homes in the Fan Road area -- including some that were self-built. There were obviously some homes built with poor construction methods, but not all of them.

One home I'm intimately familiar with (because I grew up in it), was located on a road in which most homes were completely destroyed, a few had the top blown off, and a handful escaped with serious roofing damage. I watched our home be built as a child and walked the construction site many times. It was by no means the absolute tip-top in construction, but it was definitely high-quality. Since it only had severe roofing damage, it is not a good example, and would actually give credence to the idea that well-built structures didn't have significant enough damage to prove an EF-5 rating. However, considering that our former home was likely on the edge of part of the tornado it really isn't evidence either way.

My reason for posting, however, is to reject the statement that high-quality construction was not present in Pleasant Grove or Concord. This is a ridiculous statement, and should not be made on the basis of Internet research and looking at a small sample of photographs.

We do not know how many overall structures the NWS looked at or if there were well-built structures that either they didn't survey, didn't know about, or had already started debris removal. But, I know ABSOLUTELY that there was high quality construction in Pleasant Grove in the Fan Road area. Not only have I been in dozens of the homes prior to their destruction or being damaged, but I watched many of them being constructed, and even went inside them during the construction phase.

As a homeowner for nearly 15 years now, and someone who has taken a serious interest in construction quality of homes (I'm far from satisfied with my current residence that I bought while less than 25% complete), I may not have a degree in mechanical or civil engineering, but I certainly understand how homes are constructed and how construction quality is part and parcel of assessing the DIs for tornadic damage under the Enhanced Fujita Scale.

I've no reason to believe the EF-4 rating is wrong or inaccurate, but let's not make broad conclusions about construction quality from mere photographs of a SMALL sample. That's not a valid scientific approach if accuracy is a concern.

Let's also not say that EF ratings don't involve opinion. Of course they do. They require subjective human opinion. That's simply the methodology, and while there is room for improvement and continued refinement and standardization, when humans are involved opinions are absolutely part of the process, and no matter how rigorous the approach it will still be subjective at the end of the day. It is what it is.

A case can be made that the Tuscaloosa tornado was an EF-5, but 6 years after the event it isn't really possible to rebut the evidence for an EF-4 rating.

I do think, however, that great questions were raised, and the original poster has gotten to the heart of the debate over every tornado rating. How much of this is truly objective and bias free? How much is subjective and colored by human perspective and experience?

Yes, there are wind tunnel tests, load testing, and other engineering studies and processes that have given us a much better understanding of the force needed to create certain categories and types of damage. But you can't recreate a forest and exact soil types in a lab just as you can't test an identical complete structure and foundation in lab. You can approximate, hypothesize, and extrapolate, but we lack the funding and research to do an absolute 1:1 comparison.

The EF scale is far superior to the F scale and decidedly more accurate in a host of ways, but it is not above reproach and certainly has its flaws. And as long as a human element is involved, and dozens of variables are involved, there is really zero way to be completely CERTAIN about anything. That's why confidence intervals are so frequently used in science, and something like that would be absolutely beneficial to the EF scale.

Instead of saying X tornado was an EF-4. Give a confidence interval that it was an EF-4. Give an interval that it was an EF-3 or EF-5 as well. I know the general public wouldn't really understand that compared to what we have know, but is the EF scale even that digestable for them right now?

If science is the interest, then we need to be honest about what we don't know as much as what we do know. And we simply don't know for sure what winds are in any given tornado or what forces were brought to bear on a particular structure. All we can do is use the scientific method to get as close as possible.

 

[ARCC]

JRC,

I'm not exactly sure what you are arguing. No one is offended about what you think about the rating, but this is a weather forum and when you post an opinion, you set the stage for someone to disagree with you.

I highly doubt Joplin would have recieved the EF5 rating had the pavement markers not been noticed. So truthfully it is possible that the surveyors may have missed something that would have reached the EF5 rating. The problem is that no other contextual damage indicator I've seen backs that assertion up such as cars were not launched as Buckeye stated. In Joplin that damage looks more severe than Pleasant Grove and several more contextual indicators backed up the EF5 rating. If you want to make a case for EF5 for this tornado, use the damage after it passed Tuscaloosa such as the mauling it did to the train bridge.

I didn't agree with the EF4 rating either at first, but as I examined the clear cut cases of EF5 damage from the big four, it's hard to find a comparison.

 

[Kory]

Prior to the tornado, I had been in the basements of well over a dozen (more like two dozen plus) of the homes that were destroyed. Some of the homes destroyed are homes that I spent considerable time in as a child, pre-teen, and as a teenager.

I know for a fact that the quality of construction varies considerably -- you had at least 6-12 if not more homebuilders that constructed homes in the Fan Road area -- including some that were self-built. There were obviously some homes built with poor construction methods, but not all of them.

One home I'm intimately familiar with (because I grew up in it), was located on a road in which most homes were completely destroyed, a few had the top blown off, and a handful escaped with serious roofing damage. I watched our home be built as a child and walked the construction site many times. It was by no means the absolute tip-top in construction, but it was definitely high-quality. Since it only had severe roofing damage, it is not a good example, and would actually give credence to the idea that well-built structures didn't have significant enough damage to prove an EF-5 rating. However, considering that our former home was likely on the edge of part of the tornado it really isn't evidence either way.

My reason for posting, however, is to reject the statement that high-quality construction was not present in Pleasant Grove or Concord. This is a ridiculous statement, and should not be made on the basis of Internet research and looking at a small sample of photographs.

We do not know how many overall structures the NWS looked at or if there were well-built structures that either they didn't survey, didn't know about, or had already started debris removal. But, I know ABSOLUTELY that there was high quality construction in Pleasant Grove in the Fan Road area. Not only have I been in dozens of the homes prior to their destruction or being damaged, but I watched many of them being constructed, and even went inside them during the construction phase.

As a homeowner for nearly 15 years now, and someone who has taken a serious interest in construction quality of homes (I'm far from satisfied with my current residence that I bought while less than 25% complete), I may not have a degree in mechanical or civil engineering, but I certainly understand how homes are constructed and how construction quality is part and parcel of assessing the DIs for tornadic damage under the Enhanced Fujita Scale.

I've no reason to believe the EF-4 rating is wrong or inaccurate, but let's not make broad conclusions about construction quality from mere photographs of a SMALL sample. That's not a valid scientific approach if accuracy is a concern.

Let's also not say that EF ratings don't involve opinion. Of course they do. They require subjective human opinion. That's simply the methodology, and while there is room for improvement and continued refinement and standardization, when humans are involved opinions are absolutely part of the process, and no matter how rigorous the approach it will still be subjective at the end of the day. It is what it is.

A case can be made that the Tuscaloosa tornado was an EF-5, but 6 years after the event it isn't really possible to rebut the evidence for an EF-4 rating.

I do think, however, that great questions were raised, and the original poster has gotten to the heart of the debate over every tornado rating. How much of this is truly objective and bias free? How much is subjective and colored by human perspective and experience?

Yes, there are wind tunnel tests, load testing, and other engineering studies and processes that have given us a much better understanding of the force needed to create certain categories and types of damage. But you can't recreate a forest and exact soil types in a lab just as you can't test an identical complete structure and foundation in lab. You can approximate, hypothesize, and extrapolate, but we lack the funding and research to do an absolute 1:1 comparison.

The EF scale is far superior to the F scale and decidedly more accurate in a host of ways, but it is not above reproach and certainly has its flaws. And as long as a human element is involved, and dozens of variables are involved, there is really zero way to be completely CERTAIN about anything. That's why confidence intervals are so frequently used in science, and something like that would be absolutely beneficial to the EF scale.

Instead of saying X tornado was an EF-4. Give a confidence interval that it was an EF-4. Give an interval that it was an EF-3 or EF-5 as well. I know the general public wouldn't really understand that compared to what we have know, but is the EF scale even that digestable for them right now?

If science is the interest, then we need to be honest about what we don't know as much as what we do know. And we simply don't know for sure what winds are in any given tornado or what forces were brought to bear on a particular structure. All we can do is use the scientific method to get as close as possible.

That bolded paragraph is the main point. Proxies are only as good as the independent testing done and there is no way to recreate EXACT specifications. Even down to testing a board of wood, each one will have different planes of weaknesses when stress/strain are applied. And because we cannot recreate those stress/strain patterns from a specific tornado on that specific piece of wood, there will be error (how great of an error depends on the sample size of experiments). Now, expand that to structure testing...it can become much more complicated.

By the way, this is NOT an affirmation or disapproval of the EF rating. Just one main issue I find with proxies....

 

[JRC]

JRC,

I'm not exactly sure what you are arguing. No one is offended about what you think about the rating, but this is a weather forum and when you post an opinion, you set the stage for someone to disagree with you.

I highly doubt Joplin would have recieved the EF5 rating had the pavement markers not been noticed. So truthfully it is possible that the surveyors may have missed something that would have reached the EF5 rating. The problem is that no other contextual damage indicator I've seen backs that assertion up such as cars were not launched as Buckeye stated. In Joplin that damage looks more severe than Pleasant Grove and several more contextual indicators backed up the EF5 rating. If you want to make a case for EF5 for this tornado, use the damage after it passed Tuscaloosa such as the mauling it did to the train bridge.

I didn't agree with the EF4 rating either at first, but as I examined the clear cut cases of EF5 damage from the big four, it's hard to find a comparison.

ARCC, good morning. I am not attempting to argue, if it is coming across that way then my apologies. With this being a message board and all you are able to do is read letters on a screen, facials expressions and voice are absent. Meanings can be misconstrued.

The confusion I had was how an observer could definitively state "was absolutely not....", "in no way shape or form....", etc. The EF rating is subjective. Evan articulated this point very well.