Enhanced Fujita scale confusion

[rdale]

The tendency is for this to pull ratings down, as once you get multiple ratings you become concerned that your skills will be questioned and try not to attract scrutiny, but also there can be political pressure from local officials to rate a storm in a particular way.

I'm just curious how you came to this conclusion based on your location? I've never sensed "political pressure" to downgrade EF scale numbers in any scale I've taken part in. If anything, citizens get upset because they want the higher numbers. Do you have any specific cases where this happened?

 

[STurner]

I know what you mean. The EF-scale although not as much as the F-scale has subjectivity. The recent Askewville, NC. tornado seemed to arguably have some low-end EF4 damage. I sent Tim Marshall to see what he thinks and clear up what I may or may not be seeing. As far Stoughton goes it arguably could have been rated F4 and even the Westminster twister from 2006 may have more than an argument for an F4 rating. The man who did the 122 mile monster in Arkansas is more conservative than most surveyors as to why it may not have gotten an EF5 rating. The most recent St. Louis damage in subdivisions did not seem any worse than some of the damage I observed in North Carolina. Also construction can be very hard to tell and even I know little about it.

 

[J Allen]

Don't disagree with the ratings in Jackson, haven't looked at the resources available (the biggest problem here is getting structural information) to give a rating but from my limited viewing the rating given doesnt seem unreasonable.

Perhaps I have not been clear in what I am trying to communicate here, the problem is that we have a completely subjective scale system which relies on all buildings conforming to the building codes commonly found within the US, the people given the ratings all having the same experience (picture a person giving a rating to a high end EF5, and then giving a rating to a low end tornado of a similar damage scale the following week or year, based on the intense damage seen in the first case and the open end of the scale he may be more likely to rate what might be EF5 to EF4 based on this as is suggested in the post above). What we have is a subjective opinion based scale(like the Mercalli Intensity Scale for instance), when what we want is an objective scale (ie. a Richter scale). Doswell's (2009) assertion that the lack of consistent damage indicators which are able to provide indication of EF4 and 5 damage is a real issue given the small are affected by tornadoes in the first place. When we add the complication of money involved, people's emotions we have a massive quandry where this scale is subject to a number of failures. To unravel a whole kettle of worms the 2002 La Plata tornado was a fairly good example of the bias associated with subjectivity. And we still have no real analysis of the windspeeds commonly associated with a particular scale of tornado (missing damage indicators for instance), the categorisations in the EF-scale are based on "expert" opinion rather than real measurements.

The discussion does seem to produce somewhat complex arguments to assess whether it is effective or not. If a Quick Response Team type response by more expert NWS rating staff for high end events was applied there would probably be more objectivity (how many raters locally have been exposed to EF5s in all honesty? The application of the scale is in as much experience as knowledge of the indicators, it also assumes sufficient knowledge in structural engineering which is not usually pre-requisite for those who rate). But then there are funding limitations to this application.

Anyway, happy to leave it there, was just trying to raise some of the issues of the scale beyond the simple rating...its far more complex than just damage indicators.

 

[rdale]

I guess I'm confused about a few things... Having worked in Federal funding after tornadoes, I can guarantee you that the EF number has -no- bearing on that process. It's entirely based on the amount of uninsured damages.

And there is no policy that tornadoes are ranked EF3 by default as a max. I just saw news that yesterday's STL tornado was rated 4.

Yes it is still subjective. It always will be. But to say that tornado researchers are deliberately ranking tornadoes lower because of politics is simply not warranted given the evidence you have shown (none). I am certainly open to facts, but so far the only facts are pointing away from your theory.

 

[mwenzbauer]

The man who did the 122 mile monster in Arkansas is more conservative than most surveyors as to why it may not have gotten an EF5 rating.

I assume you're referring to the 2/5/08 Atkins/Clinton F4? I've always thought that one seemed a possible EF5 candidate, along with the 5/4/03 Franklin tornado. I'll be curious to see if Askewville stays EF3 or goes to EF4, that one from what I've been able to find seems to have the most extreme damage from that outbreak.

 

[J Allen]

Going to leave this debate there and take it to PM. Mods feel free to delete if necessary as this has taken the discussion off the intended topic.

 

[Greg Stumpf]

An EF4-5 rating provides an event additional attention from the media and opens a number of federal funding options, some by request of the local representatives through federal application (which tend to use the rating as a battering ram), and other by the declaration of disaster zones at a presidential level (national and international funding options open with this declaration, seems to result mainly either by widespread events, or a big publicity highly damaging event).

This is hogwash! I've been involved in official NOAA damage surveys for over two decades now, and there is absolutely no such threshold for response funding based on the tornado rating scale.

 

[STurner]

Yes the Girard/Franklin tornado from 5/4/03 seemed very similar in appearance to the Bridge Creek/Moore/OKC F5 tornado from 5/3/99 as well the Red Rock, OK tornado from 4/26/91. The Red Rock, OK tornado, The Girard/Franklin, Kansas tornado seemed like possible F5 candidates. If you remember the Harper, KS. tornado from 5-12-04 seemed very defenite. In fact it did some of the most extreme damage over a small area to a brick home and farm equipment. It was probably some of the most impressive damage I have ever seen from not only photos but aerial view as well. The Clinton/Atkins, AR. tornado from 2-5-08 at times did borderline EF4/EF5 damage. The Askewville tornado does seem very debatable as well. It seems hard to believe you can get no EF4 or EF5 tornadoes from an extremely massive tornado outbreak but get an EF4 rating from the St. Louis tornado the other day which had much fewer tornadoes.

 

[Drew.Gardonia]

personally I think the whole Enhanced Fujita scale is complete garbage.

What was once an F-0 is now an EF-1, what was an F-1, is now an EF-2, what was once an F-2, is now an EF-3, what was once an F-3, is now an EF-4, and what was once an F-4 is now an EF-5.

the entire scale change is stupid, and it should have never been tampered with to begin with.

 

[jaredleighton]

Construction variables account for A LOT of the differences. While many photos may appear to show similar damage, a really good understanding of construction methods and materials is vital.

^^^What he said.

The thing that most strikes me with the Jackson, MS tornado:
http://www.srh.noaa.gov/images/jan/Weather_Events/2011/0415severe/hinds/100_1165.JPG

is look at the trees around the blocks. The vegetation saw nowhere near EF-4 as has been thrown around here in conversation.

^^^What he said.

On this last point and addressing rdale, by have a default rating of EF3 assigned when damage greater is suspected (fairly sure this is policy) there is an inbuilt reluctance to assign a higher rating. I clarify, you are correct, citizens want higher numbers for the attention it brings, and the potential for improved funding, while federal bodies generally don't want to fund an event as much as they don't have to (the amount of damage loss means that many tornadic events are excluded). So you have citizen/local pressure to go up, institutional/government pressure to go down. My location is somewhat immaterial when it comes to talking to people who rate and reading the material that is out there. Granted, I haven't given ratings myself in a formal sense and therefore can't offer it in personal experience, but I would be surprised if this pattern was uniformly applied from what i've heard, it may vary from state to state.

^^^Not what he said.

Now whether this desire to under-rate was due to the scrutiny issues or due to policy it had an effect on the rating dearth of EF5 tornadoes in the period 2000-2007 (which recorded the zero F5 enigma after the consistency of the 1990s).

I'm not sure it's fair to dismiss the absence of a rare phenomenon such as an EF-5 tornado impacting a structure over an 8 year stretch as a political stunt (at least that's how I read it).

This is hogwash! I've been involved in official NOAA damage surveys for over two decades now, and there is absolutely no such threshold for response funding based on the tornado rating scale.

^^^What he said.

When it comes to rating tornadoes, I have never...ever heard of any political pressure from "above" to rate a given tornado a certain way. In fact most surveys are done by meteorological scientists, the same scientists who conduct a large percentage of the research papers in existence. The main goal of any survey team is to get the rating correct. This is important not only for historical purposes but for research purposes as well, and the last thing any of those meteorologists want is bad data mucking up the database.

If you're interested in how the EF Scale actually works and how to accurately use it you can look at the EF-Scale training modules by the WDTB.

 

[J Allen]

Not suggesting its a political stunt, rather a systemic under-rating during the period caused by an institutional policy which i'm sure Greg Stumpf would be happy to tell you more about.

I wouldn't say that the database in its current form is particularly useful or based on total accuracy, only database that can be given that honour is the ESWD database which actually concerns itself with quality control, but thats a whole other story.

Jared I am well and truly familiar with the EF-scale and its application. Spent a significant time investigating it out of personal interest and reached the point where its still a poor mans substitute for a real understanding and isn't solidly based on observations but alot of speculation at least to some degree, whether its our best option and better than Fujita's adjusted scale I am not totally sure, the assumptions regarding building codes and the effect of a tornadic circulation are certainly questionable.

Apologies folks, seems you can't believe everything you read these days, nor can everyone above read what was written either . Thankfully Rdale has corrected a few of the mythconceptions and misconceptions I had so Im satisfied and I will leave it there. Suffice to say that I wouldn't say the EF-scale is completely impartial and to believe it so is nieve.

 

[Greg Stumpf]

Not suggesting its a political stunt, rather a systemic under-rating during the period caused by an institutional policy which i'm sure Greg Stumpf would be happy to tell you more about.

You certainly did suggest it was a political stunt! What are you really talking about? The only institutional "policy" that raised the concerns of survey experts like me was the change in the use of the "Quick Response Team" (QRT) from a team of nationally recognized experts (of which I used to be a member) to in-house NWS meteorologists with survey experience. But that has nothing to do with lowering ratings based on saving government disaster payouts, which is as I said, complete hogwash.

Suffice to say that I wouldn't say the EF-scale is completely impartial and to believe it so is nieve.

Of course the rating system, both the F- and EF-scales, have a large degree of subjectivity. They aren't based on instrument measurements, but by evidence in damage. Not every surveyor comes to the exact same conclusion on events, and the "accuracy" of those conclusions are based on experience level. But even Tim Marshall, probably the world's foremost wind damage assessor (and it's his studied profession) will provide you a range of suspected wind speeds based on observed damage, and sometimes that range will span across two scale categories.

 

[Jake Orosi]

I don't know about funding thresholds, but some tornado-devastated communities seem to use F-ratings of storms as some sort of source of community pride. I may be wrong, but maybe you guys can help me out - I seem to remember one particular Plains town being devastated a few years back; the NOAA preliminarily rated it an F5, but subsequent scientific investigation caused them to "downgrade" the final rating to F4 - still incredibly destructive of course. But for some reason that's quite beyond me, the community was shocked and incensed by the NOAA's scientific findings...made t-shirts that said things like "'Not an F5', my a**!" and such. It seems as if they felt that designating the tornado an F4 was somehow either an attack on the town or a downplaying of the damage the tornado caused.

 

[Tim Shriver]

The Jackson image shows, from what I can see, there are no straps or bolts that would secure the house to the foundation.

The foundation itself appears to be brick, non-reinforced. Not sure what the house was made of itself. I see timber off to the left. Did it just move the house off the foundation?
The trees that can be seen are not debarked. No uprooted trees either. Smaller tree damage.

Without seeing to the left of the image I would suspect that is where the remaining part of the house is, if not the full house (with damage)

I suspect the rating of EF-3 to be correct. The Damage Indicators and Degree of Damage are consistent with an EF3.

Brick can handle a great deal of downward force, but by itself does not do well with side forcing.
Thus a car can drive through a non-reinforced brink wall from the side, but try it downward into the wall, the car will loose every time.
Again, the photo is limiting.

The second photo you cannot see the foundation and how the house was secured to it. Stoughton was a powerful tornado (multi-vortex at times)
and from what we saw many houses that were bolted to concrete foundations were destroyed. It was high end F3 and in many spots the DOD indicated low F4.

Again the images are limited as a wider view of things would be needed for fully rate it.

Tim

 

[Tim Shriver]

That *used* to be the case. However, it is my understanding, from different sources, that the National QRT no longer exists. It used to consist of selected damage experts, with the goal of supporting damage assessments for high-end tornadoes. However, there may still be separate QRTs organized by each NWS region, and they may or may not be called for any particular event. Why this resource (the national QRT) went away, I do not know. Now, it may be a budget issue, but how much does it really cost to bring in a couple of experts (e.g. Tim Marshall, NSSL/WDTB damage scientists, etc.) for a few events every year? It's neither here nor there now, regardless.

Each WFO does the damage assessments in its CWA. For large events other teams can be brought in.
Our group, is trained and has an active Damage Assessment Team (DAT), trained by the NWS over the years.

We go out and assign what the DI (Damage Indicators) are and the Degree of Damage (DOD). Structure by structure.

We assemble this information along with maps of the path, images and video of the damage, interviews from affected people and witnesses.

We submit this to the WCM and he assigns the EF rating. It is not hard to tell
what the EF rating is with the collected information and we know what it is
before submitting the information to the WCM. But he makes the final "public" call.

If they question our finding, they will take us out and reexamine the data, but so far
we have been spot on.

Tim