Where have all the violent tornadoes gone?

[Tony Lyza]

The picutres that Sheila shows look like structures just collapsed down. You see tons of debris, which tends to be centrifuged out in violent tornadoes. It's tough to get perspective since the pictures are pretty zoomed in (what does the entire neighborhood look like?) , but the trees in the 2nd pic don't look like they're too bad off, and there isn't much damage to the surroudning houses (in the background). Again, this analysis is pretty trivial, since we don't have the entire overview from which this pictures were taken. If those are two structures destoyed amongst an entire neighboorhood, can we really say much about it? Would a tornado "strengthen" for 40 feet if it's moving at 45mph? I mean, I'm sure it could, but I think chances are better that either the structures were more poorly built or something big smashed into them. Again, however, this analysis is fruitless since we've seen time and again that impressive debris doesn't necessarily equal impressive tornado (intensity-wise). 130mph can "wipe a slate clean", which is why we need some engineering analysis to give us a little objectivity amongst the first impression "wow"s.
[/b]

Just looking at the pics and knowing that a well-constructed home being leveled in F4 on the Fujita Scale, I would definitely say that Gallatin was F4. Keep in mind that this was a compact multiple-vortex tornado per the available video. Just look at Xenia, OH, damage, where there was F5 damage very near F1 damage. Yet, we don't question the rating of the Xenia tornado.

 

[mikegeukes]

I have posted this before and numerous other links to the F-Scale
Read the sections: Problems on the high end of the scale

A Guide to F-Scale Damage Assessment
http://meted.ucar.edu/resource/wcm/ftp/Fin...ssmentGuide.pdf

Mike
http://www.chaseseason.blogspot.com/

 

[Greg Stumpf]

...the Gallatin tornado for instance plowed through some very large (some brick) homes.[/b]

Brick construction or brick veneer? Big difference! I'm willing to bet the latter.

 

[Dan Robinson]

This smaller house near the large brick homes had a brick veneer. I can't vouch for the big houses as we couldn't get close to that area.

http://wvlightning.com/april72006/gallatin7.jpg
http://wvlightning.com/april72006/gallatin5.jpg

 

[Bill Tabor]

If there is some special interest group politically changing the way tornadoes are rated, me and my damage survey colleagues are completely unaware of it. I think this assertation is treading on the thin line of government conspiracy theories, which, IMHO, is ridiculous concerning something as simple as a difference in one rating level for certain tornadoes. In the grand scheme of things, this doesn't make much of a difference, and bear in mind that the F-scale and the EF-scale are still loaded with subjectiveness. One need only take the following exercise with a large group of folks to see what kind of distribution of F-scale ratings can be applied among multiple surveyers given the same damage indicators.
[/b]

I wasn't trying to imply any conspiracies in that regard like alien invasion, who shot JFK, etc - only that the NWS and related government budgets are controlled in the real world by funding based on support in the public sector and also by large funding PAC's providing support and campaign contributions to legislators. It is in that regard that I consider there may be a slant for the longer term in affecting these eventual changes. Note that if that is true the reasoning behind it may not really be widely disseminated to those doing surveys. Also, I am not saying that this is the case, only that I wonder if this is part of the change to a new ratings system and in more conservative ratings before that. Of course you will probably say 'Yes, and the conspiracy is to make the ratings more accurate which is in line with the scientific goal'. It is hard to argue with that. But I suppose my real question and intent that I was trying to solicit was 'Does the government, insurance companies, or any other entity benefit by mostly eliminating F4's and F5's?'. If the answer is no not really than I guess I am off here. If on the other hand, there is some leeway then perhaps that should be considered.

I agree that the higher skill level and criteria to better define damage of the EF scale is a step toward the more scientific and possibly for the better as long as you are still obtaining your mission goals. I think the biggest objective in question is that of trend and historical studies. With that said, that may not be a good enough reason not to go to EF or to not be very restrictive in giving out F4 / F5 ratings, but the implications should be considered.

As for the changing nature of the historical database, one simply needs to look at the dramatic increase of tornado reports starting in the 1950s. Harold Brooks deals with this all the time in his climatological studies, and there are ways to correct for these reporting changes over the years. [/b]

I don't totally agree with that. It would never be as good as a consistent data set. You can manipulate statistical data in various ways to account for such situations but that is always based on assumptions of the data. Lack of data, or inaccurate data will lead to incorrect assumptions and will skew the results. The more you change your dataset over time including reporting points, reporting criteria, ability to collect incidents, rating criteria will greatly affect your results. That said, if you don't have a choice then you just make do. My point was that any changes in bias related to difficulty in obtaining F4/F5 or change to EF will further skew future result sets, and this is important and should be considered before allowing such things to happen. Alex indicated old F-scale was really based on 'rate the damage not the tornado'. If this is true then we have seen a dramatic paradigm shift IMO because the trend is to try and more closely approximate the tornado wind speeds based on the damage. The original scale may have obviously been off on those wind range damage scales, but that was a given. The focus was to rate based on what had occurred and not based on construction technique. If a slab was wiped clean it was an F5 pure and simple. This is no longer true today.

 

[Greg Stumpf]

If a slab was wiped clean it was an F5 pure and simple. This is no longer true today.[/b]

Like I've already said here and here, the jury is still out on this one.

 

[Kevin Scharfenberg]

Regarding the 4/7/06 Gallatin, TN tornado being rated F3 and not F4, it was suggested earlier in this thread that homes being worth hundreds of thousands of dollars and being in a locality with building codes doesn't necessarily mean they can't be blown away with a tornado with winds weaker than F4. Now comes this new story from a Nashville TV station:

http://www.wsmv.com/global/story.asp?s=4833787

Duty is convinced problems with the original construction made his house and the other homes, where people died, vulnerable and weak. He maintains his house did not meet Gallatin's building codes, and he had filed suit against his builder even before the tornado.

"The way the house was fastened together, the nails that were used, the the way the drainage system around the foundation was depositing water right at the foundation, it made the house very vulnerable," he says.

A bricklayer told him there were not enough brick ties to even hold the bricks in place.

"The bricks were literally just standing in front of plywood," said Duty.
[/b]

If this turns out to be true, that F3 rating is looking better to me every minute.

 

[Joe Nield]

Regarding the 4/7/06 Gallatin, TN tornado being rated F3 and not F4, it was suggested earlier in this thread that homes being worth hundreds of thousands of dollars and being in a locality with building codes doesn't necessarily mean they can't be blown away with a tornado with winds weaker than F4. Now comes this new story from a Nashville TV station:

http://www.wsmv.com/global/story.asp?s=4833787
If this turns out to be true, that F3 rating is looking better to me every minute.
[/b]

I'm willing to bet that this is very widespread. I've indirectly monitored the construction of a subdivision across from my parents' house for the last 10-12 years, and each time, homes are thrown up in a matter of days or a few weeks. I firmly expect the homeowners to have several problems with them over the next several years.

I call them tornado fodder...you just know an F3 is going to come through there someday and level the joint.