Enhanced Fujita Ratings Debate Thread

[A Guy]

Would like @A Guy input on cycloid stuff, very knowledgeable on this topic. I believe cycloid analysis has very legitimate merit fwiw, but only when carried out in a careful manner (and not applied in every circumstance) Can’t go into much details here atm but I might in a later post

EDIT: also, I would absolutely not designate it as pseudoscience, that’s a massive stretch to me.

I don't have any special insights, all I can say is that I read the relevant literature when those that called it pseudoscience usually had not (and even if something is wrong, that doesn't make it 'pseudoscience' specifically). It's based on assumptions that are reasonable, if not strictly correct, and a reliant on geometry that doesn't particularly special (though I couldn't do it myself, but I'm increasingly realising that my school maths education was actually appalling and missed a lot of useful things).

There are some unanswered questions I think are worth considering:

- The method assumes that the marks are produced from a point, but it's not clear to me from simulations that's actually the case. The issue this raises is whether the marks are representative of windspeed at all.
- The method assumes that the marks are regular, i.e. that both the speed relative to, and distance from the centre are steady. Both the fact that real-life marks are often visibly distorted, and tornado simulations show that neither of these assumptions is true (which is what Fujita was trying to get around when he studied the 1965 Greentown tornado). How much does this matter?
- Most analyses I've seen correspond to EF-scale windspeeds. However, the marks are generated at very low levels, so it's not clear how these correspond with standard gust values (i.e. 3 seconds at ten metres or similar). The modelling I've seen on ground marks was on a metre scale, but something on a significantly finer scale would be more informative.

That said I don't think the assumptions and unknowns are tremendously more problematic than some of those behind EF-scale damage analyses.

 

[Grand Poo Bah]

I'm surprised 2002-2007 hasn't been mentioned very much as an era to reexamine. Definitely one of the peak periods of egregious conservatism, which is important because it created a lot of the justification for eventually rolling out the EF scale.

 

[Grand Poo Bah]

This is not going to be a popular take on this forum, but I’ve silently reached the conclusion that Chapman might not be upgradable, at least from a structural damage perspective and considering NWS survey standards. I did a deep dive looking at every angle of the main farmhouse in question. The first thing I noticed was that the portion of the foundation stem wall that got cracked and ripped apart, may have been cracked prior to the tornado and been a pre-existing weak spot. The reason I say this is that the crack happened right where “corner pop” occurs. Corner pop is the cracking of foundation corners caused by expansion of brick veneer caused by temperature changes. The Chapman farmhouse was brick veneer. Also, the foundation had two sections: a larger basement portion and a smaller crawlspace portion with a concrete stemwall (that’s the portion that had its corner buckled). There were two more problems I noticed, the first of which was that none of the sill plates on the main basement portion were removed. Not a single one. While I think factors like “not enough” sill plate removal are dubious amid extreme contextual damage (*cough* Saltical’s analysis of the Wicker Street home *cough*), I do consider ZERO sill plate removal and bolt bending to be a sign of an anchoring problem. It may seem pedantic, but it is a clue that signifies a real problem, specifically that the bolts and plates didn’t do their jobs and didn’t put up much of a fight as the house was removed from the foundation. The smaller crawlspace portion did lose sill plates however, which suggests some kind of inconsistency in the construction between the two foundation sections. In addition, the third problem was that the crawlspace portion was pretty much buried under a layer of debris, which may classify it as a DOD9 rather than a DOD10. If Chapman has a path forward for an upgrade, it will probably rely on the tree, railroad, and farm machinery damage, but I’m not exactly sure what the main basis would be among those three things.

This is why I'm so interested in the methodology they'll be using to reanalyze these tornadoes. If it's a Grazulius style analysis, the house wouldn't need to be the sole deciding factor for a new rating. There's so much more to look at contextually. However, I also don't know what the basis would be for rerating the contextual damage. Major head scratcher. Maybe it's just a case of all the evidence being collectively very supportive of "highly-probable EF5 wind speeds".

Another big question is if the Lyza team's process is going to remain entirely confidential, or will we see several small publications (like Fujita used to publish) related to forensic analysis and the progress of our understanding? If it's the latter we certainly won't run out of things to discuss here.

I really want to see more statistical analysis of lofted objects. Ladue sounded extremely skeptical about vehicles as a violent tornado DI, but I think there's more effective ways to incorporate thrown objects into the EF scale. For example, probability curves based on an objects general volume, mass, and distance traveled. Maybe all three variables could be used in an algorithm that generates a final score. The final score would then determine the rating. Surely, with enough Monte Carlo simulations a methodology could eventually be developed. This might actually be what Connell Miller and team are already working on now that I think of it.