Was Joplin really *not* an EF-5?

[Elaine Spencer]

Thought this topic could use its own thread... mods feel free to move or merge if appropriate.

A report by the American Society of Civil Engineers found no evidence of true EF-5 level damage from the 5/22/11 Joplin tornado:

http://www.joplinglobe.com/topstori...ineers-release-study-of-Joplin-tornado-damage

Here's a link to the actual report (but you have to pay $50 to get it):

http://www.asce.org/Product.aspx?ID=2147487569&ProductID=175469628

Some outlets are billing this story as proof that Joplin was not *really* an EF-5 after all. I wouldn't jump to that conclusion just yet (though others might). The NWS does not plan to change its rating at this time.

The report, from what I gather, states that all the structural damage examined COULD be attributed to lower wind speeds -- as low as EF-2 for many structures -- due to the way they were constructed. That doesn't necessarily mean higher wind speeds didn't occur, it just means they can't be proven based on structural damage alone.

In any event I think this report raises a number of significant issues:

1. Contrary to the currently popular belief that nothing above ground can survive a violent tornado, it IS possible to significantly mitigate damage through relatively simple measures such as use of hurricane clips. (The City of Joplin is requiring these in all new construction.)

2. Use of non-structural damage indicators (such as concrete parking blocks and manhole covers being moved) in some cases.

3. The overall limitations of damage surveying as a reliable indicator of tornado strength.

4. Since Joplin was the inspiration for the Impact Based Warnings experiment and its warnings of "catastrophic" and "unsurvivable" damage -- if this tornado turns out NOT to have been as violent as previously thought, what implications might it have for IBW?

Anyway, have at it.

 

[Mike Johnston]

At least it appears Joplin officials are taking recommendations for improving building codes seriously. According to Nancy Mathis's book Storm Warning, in the wake of the May 3, 1999 tornadoes, Texas Tech sent a team to survey the damage. They found significant deficiencies in building code standards and enforcement, even to the point that new/replacement construction was being done with the same shoddy standards as before. When the Texas Tech crew tried to give some recommendations to Oklahoma officials, they were basically told to go back to Texas. Hopefully, we will live and learn from our mistakes.

 

[rdale]

4. The fact that Joplin was the inspiration for the controversial Impact Based Warnings experiment with its "catastrophic damage" warning messages, and what this report says about its basic premise (that more lives would have been saved if only the NWS had told everyone to "get underground or die").

I see no mention of that at all... Can you clarify where that is in the report?

 

[Dave C]

I'm slightly skeptical of civil engineers in certain contexts. I don't want to say more than that to avoid offending any CEs on the board, but I have worked with plenty and there are certain contexts where their methods may or may not be appropriate or accurate. In this case I am not thinking their experience and methodology is going to be any better than the NWS damage assessment.

I've recently read claims by other civil engineers (cannot locate the article but it was mainstream media) that simple hurricane straps would have helped Moore - yet when swirling debris, pressure drops, fires, flooding, differential wind directions, multiple vortices all come with a tornado, I just don't buy it. The CEs like to treat tornadoes as straight line or hurricane winds and think that its all that simple. Seems flawed logic to me.

I'm not against increased building standards. It certainly would help where tornadic winds are lower - but I think these engineers badly underestimate and over simplify the collection of challenges that a tornado can throw at a structure. Once something is shredded by debris, its structural integrity is gone anyway, no matter what it was designed to withstand.

 

[rdale]

Hurricane straps would not help a direct hit. They would be a MASSIVE help for many of the homes that were damaged.

 

[Shawn Schuman]

Hurricane straps would not help a direct hit. They would be a MASSIVE help for many of the homes that were damaged.

Exactly. Same deal with the requirements in Joplin. There's no way any quality construction methods are going to much of a difference in a direct hit from a violent tornado, but in most other instances they could very well help and possibly save lives. The vast majority of homes are not going to sustain a direct hit from a violent tornado, after all.

 

[Elaine Spencer]

I see no mention of that at all... Can you clarify where that is in the report

I apologize, I didn't word that very well. I meant "what it says about" in a figurative, not literal sense, as in "What does the kind of car you drive, clothes you wear, etc. say about you?" I have edited the post to be more clear.

 

[Chris Nuttall]

I haven't read the report, but I wonder if they only took the structural damage into account. Wasn't there some talk of unofficial DIs being used by the NWS survey team to "confirm," or lead higher confidence to the EF-5 rating? For example, I seem to remember the mention of the lofting and throwing of concrete parking blocks. I could be wrong, though. That may have just been anecdotal accounts from other people that saw the damage.

 

[Shawn Schuman]

Yeah, EF5 was based on (or at least confirmed by) concrete parking stops ripped up and thrown 50-60 yards and manhole covers pulled up and thrown. For example:

 

[Marcus Opitz]

I've been told of first hand accounts of roof drains being sucked out of the lightweight concrete deck they were originally set in on commercial buildings there. The semi wrapped around a tree with barely anything left casts doubt that this storm was less than EF5 or "old" "F5".

 

[Shawn Schuman]

No one is suggesting Joplin wasn't an EF5. At least, I'd hope no one is suggesting that. It's just that there may not have been any homes of "superior construction" that could be used to verify an EF5. You make an interesting point about vehicle damage, but I'm not so sure that could be used as a basis for a rating because there are so many variables that'd be really hard to account for. For example, this used to be a Jeep Cherokee:

Was it thrown? If so, how far? How can you know that it didn't hit the ground in between? Did it hit something, or was it hit by something that caused additional damage? Lots of questions that I'm sure would affect how you'd rate it as a DI, and even then I'm not sure you'd be able to come up with an accurate wind speed range.

As for that Jeep above, it was actually rolled/tumbled a hundred yards or so from a nearby parking lot at the hospital, and the tumbling action probably caused just as much damage as if it had been thrown half a mile or more. It's also unlikely it was affected by EF5 winds since it was on the southern fringe of the damage path. I wish we could devise usable DIs from vehicles, but I don't think it'd be easy.

 

[James Hilger]

How much wind does it take to move a hospital? I know there's no answer and I've seen Tims survey but pretty amazing.

 

[Greg Higgins]

from Shawn's comment, "Yeah, EF5 was based on (or at least confirmed by) concrete parking stops ripped up and thrown 50-60 yards and manhole covers pulled up and thrown. For example:"

Tim Marshall made a presentation of the Joplin storm at our local AMS chapter meeting and pointed out the drain covers and concrete parking blocks and stated that they were NOT used as DI's for calculating the EF rating. He did state that more information would be needed before these types of phenomena could be used for DI's. We also discussed "road scouring" as another type of DI that would need additional research.