The Fujita Scale Controversy

[Drew Terril]

I'll preface this by saying I'm not a met or an engineer. With that said, a good chunk of my time out of high school was doing residential construction, so I'm very familiar with the processes involved having done it much of my early adult life. In the areas I worked in, codes haven't changed since before I was in the field. Outside of those areas that have actually strengthened their building codes, it's difficult to find EF-5 DIs. With the vast majority of damage pics I see, I find (usually at a glance) where corners were cut in the construction process. In a lot of the poorer areas in particular, so many builds are funded by HUD, which will not pay for anything beyond what's needed to meet local code. My old boss when I was working for him took a HUD contract once, and he was so disgusted with how much they limited him that he never took another HUD contract again. CME foundations, bare minimum code compliance, inadequate amount of anchor bolts (which are already compromised to begin with when using a CME foundation), no hurricane straps. Basically we weren't allowed to build the HUD house to the same standard that we built everything else. I will also add that, for insurance purposes, a house that takes EF3 level damage is almost always going to be a full teardown and rebuild. Even at that point, it's structurally compromised enough that simply repairing what was damaged is not good enough. Think of it like an aluminum can. Once you bend the aluminum, it's much easier to crush it the second go around.

I personally am not of the opinion that DOW readings should be an automatic override when considering upping a rating if the other contextual clues don't match up. I also don't think "I think it was" should be enough either. I'm fully on board with it being yet another tool in the toolbox, but nothing more than that.

I do think a lot of the outcry that we see on social media on the subject tends to fall more or less in one of two groups. One, chasers who were on that storm and want that feather in their cap. Two, the perpetually online who always find something to be outraged about. Obviously, there are exceptions to that, but most of what I see on the subject when I do see it falls into one of those two.

Instead of constantly debating ratings, I would rather find out what can be done to improve building quality and techniques, even on the well built structures. I realize that at a certain point nothing will hold up, but that's the big thing that has me considering civil engineering over mechanical when I start working on my degree again. A big part of my wants to be a part of that side of the process, and while much of the weather enthusiast/chaser community complains about the involvement of engineers in the process, I'd like to see more of them involved. While I'm sure there are some mets out there who have worked construction in the past, or have an engineering background like Tim Marshall has, the vast majority do not have the trained eye that someone like me or a civil engineer would have. And that's where I would be happy to pull the burden of surveying storms from them and let experts in construction take that on. I have no doubt they work hard at it, but it's asking a lot to demand someone that primarily goes off a checklist to assume that workload.

 

[Randy Zipser]

Please see the attachment below: it is a comparison between the original F-Scale and the 2007 EF-Scale, with emphasis on the windspeed-range interval sizes (mph).

The first thing you'll notice is that the F-Scale and EF-Scale differ in interval sizes by a relatively small amount: 40-60mph difference from F1 to F5 (F0 was excluded since it has no specific lower-bound) and 20-40mph difference between EF0 and EF4 (EF5 was also excluded because it has no upper-bound).

One way to improve the current EF-Scale would be to incorporate actual archived data that likely already exists since 2007, when the EF-Scale was first introduced. In fact, Harold Brooks (SPC) and Tom Grazulis (Tornado Archivist & Publisher) might already have these data. The idea is to do an analysis for the CONUS showing the percentage of each EF-level (0-5) with respect to the total number of tornadoes that occurred in each year between 2007 and 2024, the last full year that such data would be available. Then, determine the 17-year average percentage for each EF "level." The end result would be a breakdown by percentage for each EF "level" over the last 17 years, which would be a reasonable period of time for a statistical data sample. Finally, a new EF scale, or as I discussed in a previous post, an "RF scale," would then be devised reflecting similar percentages per level as derived above, but that would not exceed the maximum windspeed limits that other sources of data (structural, photogrammetric, or Doppler radar) are indicating independently.

It's a "game" of playing with numbers, and actual historical long-term data from multiple sources will be input in this revision. This would be a good project for a master's thesis...gee, if only I were in college again (lol)!

 

[Tony Laubach]

Bowdle 2010 was a similar situation; rated EF-4. I don't recall the specifics as it was a long time ago, but we (our TWISTEX crew) were out with NWS for the survey the following day. High tension transmission towers were scoured off at the base and rolled hundreds of yards from their origin point. I recall the conversation about that being EF-5 level damage, however they rated it a 4 because "they didn't want the media attention" as the tornado ultimately missed town and avoided most structures.

My issue with the scale is damage done by a tornado can differ significantly based upon a variety of factors. Debris loading, particularly for a stronger tornado moving through a heavily developed area, will ultimately do more damage since there are more projectiles flying around as opposed to a tornado that moves over a more rural area.

I would love it if it were possible to take the same tornado, same intensity, size, but move it at different speeds over the same area, load more debris and see how that differs, etc. I feel like there are so many factors beyond the actual tornado that can greatly affect the damage done that ultimately gets the tornado assigned a certain rating.

Personally, in MY own opinion, I do not find it coincidental we've lacked a true EF-5 since Joplin, despite evidence of tornadoes mentioned above (Rolling Fork, Mayfield, etc). I'm not an engineer, and I haven't dug into those events enough to know whether those potential EF-5 indicators lacked certain engineering items that may have allowed them to fail in lesser winds. But I certainly wonder about it seeing the aftermath of some of these tornadoes.

Regarding the El Reno tornado... I get it... the damage done did not support the EF-5 rating. So long as that remains consistent, I will accept that for what it is.

But... my last point... we are continuing to add to the data collection mobile radar information obtained in more and more tornadoes, and I hate that most of that data isn't being better utilized. I don't know what the solution is, if there is a solution needed. But I think it goes without saying that the number of violent tornadoes is much higher than the records show, by how much, who knows. But because so many hit in areas that are less developed, they get the lower rating despite their actual strength. It's always been a pondering of mine, but alas, we work with what we've got. And the only true thing every tornado leaves behind is its aftermath... and until we can measure every single tornado somehow, that's probably how it's going to remain.