Unconventional Damage Indicators

[Ensō]

Hey guys. I was unsure as to where to post this, so I figured I'd post it here and mods can move it to a more appropriate forum if necessary. I have a whole lot of questions so I'm gonna try to organize this in a not-so-scatterbrained way. My bad on the length, I'm sure this is gonna be a novel.

Has there been any research into using unconventional (for lack of a better word) damage indicators, especially vegetation and vehicles, when doing storm surveys? I know they're used in an unofficial manner but I don't recall them being official DIs. They're rather ubiquitous even in places where other DIs may not exist, so the benefit to utilizing them is obvious.

The second part of this question I think I already know the answer to, but I'm going to ask anyway. In the absence of any other DIs, could vegetation/vehicle damage be used to assign a rating? Take for example the Ellsworth County EF4 from April 14. It did significant damage to a home near Kanopolis Lake and, though I'm not positive, I think it also caused some ground and possibly pavement scouring in the area. If it hadn't hit that home, assuming there weren't any other significant DIs that I'm forgetting about, could a rating have been assigned based on the scouring? I don't think so, but I'm not sure.

And the last part - is it even possible to use vegetation? It seems there are a ton of variables to account for that would make it very difficult and impractical to use. I'm sure soil moisture/composition, vegetation type/density/maturity, etc. would all play into that. The interaction between the tornado and the ground as well as its forward speed would probably factor in as well. And I have no idea how you'd go about testing what wind speed correlates with what kind of vegetation damage. Do we really even understand the details of the tornado-ground interaction?

[wxmeddler]

Hi there Loco!

When your talking about vegetation, are you talking about trees (aka. large stuff) or more of the shrubbery/garden type. If your talking about large stuff, the EF Scale covers that. If your talking about shrubs, I don't think they do much good and the only time that I've seen one used in a post storm assessment is when there is a weak tornado and they look for the way they are bent over to see if the entire circulation made it to the ground.

You might want to check out these links, they might provide some more insight into what your looking for

EF Scale from SPC (more interactive) (web version): http://www.spc.noaa....o/ef-scale.html

Full Version of the above with pictures (pdf): https://docs.google....iRlJ3iH1rIvCCjg

[Ensō]

I should've been more clear. I've read the documentation for the EF-scale and it's quite helpful, but I was referring mostly to grass/sod and that sorta thing. I also recall reading something about debarked shrubbery being an indicator of a strong tornado, though I can't remember where I saw it. Just trying to get an idea of whether these alternative potential DIs have ever been considered and are even feasible, considering they're among the only things that are almost always in the path of tornadoes.

I also wonder how the lack of DIs in some areas affects tornado climatology. I suppose there's no way to know how many significant tornadoes go unnoticed because they fail to impact anything, but it would seem that happens with at least some regularity. I can't help but wonder what the climatology would look like if we had more accurate and complete data.

[AtticaFanatica]

Has there been any research into using unconventional (for lack of a better word) damage indicators, especially vegetation and vehicles, when doing storm surveys? I know they're used in an unofficial manner but I don't recall them being official DIs. They're rather ubiquitous even in places where other DIs may not exist, so the benefit to utilizing them is obvious.

A lot of this type of work takes place at the Wind Science and Engineering Research Center at Texas Tech. My guess is that the problem with unconventional DIs is the cost and logistics of doing the appropriate testing to gauge what type of wind speeds do what type of damage to the feature of interest. You can't easily put a car or a truck in a wind tunnel like you can a wood or metal beam, unfortunately.

[AtticaFanatica]

I also wonder how the lack of DIs in some areas affects tornado climatology. I suppose there's no way to know how many significant tornadoes go unnoticed because they fail to impact anything, but it would seem that happens with at least some regularity. I can't help but wonder what the climatology would look like if we had more accurate and complete data.

I'm not sure how it affects the frequency distribution, but it definitely affects the EF-scale distribution, namely there's a huge underrate bias (far too many EF0's and not enough EF2's).

[Ensō]

A lot of this type of work takes place at the Wind Science and Engineering Research Center at Texas Tech. My guess is that the problem with unconventional DIs is the cost and logistics of doing the appropriate testing to gauge what type of wind speeds do what type of damage to the feature of interest. You can't easily put a car or a truck in a wind tunnel like you can a wood or metal beam, unfortunately.

Yeah, I figured that was probably a part of it. That reminds me of another thing -- can we even replicate the vertical component of a tornado? I really don't know how you'd go about doing that, but it seems to my relatively uneducated mind that not accounting for that could skew a lot of results. I guess at this point we just have to do the best we can and accept that there are going to be some uncertainties and errors. Although I would imagine the climatology is pretty messed up already given how poor the records have been until recently.

I'm not sure how it affects the frequency distribution, but it definitely affects the EF-scale distribution, namely there's a huge underrate bias (far too many EF0's and not enough EF2's).

Yeah, that's one of the things I've been getting at. I think the percentage of significant tornadoes is probably much higher than we assume. Just as one recent example, I've got to imagine several of the tornadoes on April 14 that were rated EF0-1 were much stronger than that. There were some incredible TVS/hooks and large tornadoes (based on photos/video) which ended up being rated low because of a lack of DIs. Not sure there's much you can do about that though.

[Buckeye05]

I know that the 1973 Valley Mills, TX tornado was rated F5 simply because it threw two pickup trucks an incredible distance from where they originated. The only structure it hit was a barn. I also remember a tornado in Missouri (I think) being rated EF3 for only hitting barn, reason being a heavy steel beam stored inside the barn was thrown a far distance. I don't remeber exactly when that was though. Then there are the 1990 Plainfield, and 2011 Philidelphia tornadoes which recieved F5/EF5 ratings due to ground scouring alone. Those are the best instances of "unconventional" DI's I can think of.

[Ensō]

The Philadelphia, MS tornado also threw several cars long distances IIRC, and it ripped a strapped-down doublewide from the ground and threw it something like 300 yards into a stand of trees and "disintegrated" it. It does seem that the extreme ground scouring was a primary reason for the EF5 rating though.

I think the Plainfield rating is an ideal example. I'm curious how, exactly, Fujita came to the conclusion that such crop damage was indicative of F5 winds. It certainly seems impressive, but because of the uncertainties that I mentioned earlier I dunno how you'd go about approaching that in a scientific way.

[Buckeye05]

The Philadelphia, MS tornado also threw several cars long distances IIRC, and it ripped a strapped-down doublewide from the ground and threw it something like 300 yards into a stand of trees and "disintegrated" it. It does seem that the extreme ground scouring was a primary reason for the EF5 rating though.

I think the Plainfield rating is an ideal example. I'm curious how, exactly, Fujita came to the conclusion that such crop damage was indicative of F5 winds. It certainly seems impressive, but because of the uncertainties that I mentioned earlier I dunno how you'd go about approaching that in a scientific way.

A met on here earlier said that the EF5 rating in Philadelphia was indeed due to the scouring alone. Most don't remember this, but it was listed as an EF4 for a while. From what I understand, the survey teams missed the scoured area at first, but found it in a later post survey and upgraded to EF5. The corn thing with Plainfield has always left me feeling a tad skeptical. I really wonder if that tornado occurred today, if an EF5 rating would be assigned. I do know that something similar happened in 2010. A tornado in Wilken County, Minnesota scoured a sugar beet field to dirt, and and pulled a ton of beets out of the ground. It was rated low end EF4.

[Ensō]

I'll have to see if I can find that post, I thought the other things factored in as well. I agree about the Plainfield tornado. It was definitely impressive and I'm sure it took some very strong winds to do that kind of crop damage, but I doubt it would be an EF5 today. It seems they've become very conservative recently. If the 5/24/11 Goldsby and/or Chickasha tornadoes weren't EF5s, it'd be hard to rate the Plainfield tornado as such, at least from what I've seen.

[Buckeye05]

I'll have to see if I can find that post, I thought the other things factored in as well. I agree about the Plainfield tornado. It was definitely impressive and I'm sure it took some very strong winds to do that kind of crop damage, but I doubt it would be an EF5 today. It seems they've become very conservative recently. If the 5/24/11 Goldsby and/or Chickasha tornadoes weren't EF5s, it'd be hard to rate the Plainfield tornado as such, at least from what I've seen.

I agree with the Goldsby part. The Chickasha homes weren't anchored that strong. I usually try not to nitpick surveyors but come on... these are from Goldsby btw. Note the anchor bolts, and two of these were modern brick homes. Also note the scouring and debris fragmentation (kind of a wood chipper effect seen in EF5 tornadoes). I can't conceive of an appropriate rating lower than EF5 for that. Absolutely textbook EF5. The Goldsby tornado is the only tornado besides maybe Girard 2003, and Worcester that I feel was underrated, and actually an EF5.

[Ensō]

Yeah, I was flabbergasted that the Goldsby tornado wasn't rated EF5. IIRC they decided against it because they couldn't verify that the structures had been "well-built," but it certainly looks like at least some of them were. It's even more puzzling when you consider that probably many F5s under the old scale were rated as such based on even poorer construction. If continuity between the scales is the goal, I think that's a strange decision.