Entropy Posted July 31, 2012 Share Posted July 31, 2012 That's not what you said at all. Adjusting a couple of tornadoes here and there each year would not be enough to change the overall trend as you suggested: Even if there were discrepancies between F/EF 3-5 tornadoes, that still wouldn't affect the overall intense/violent tornado count so long as they aren't weakened below F/EF 3 status. While it is true that the count for weaker tornadoes (F/EF 0-1) have trended higher due to better reporting and recognition, there has been no such notable inflation to the count for intense/violent tornadoes since their effects are much more apparent and easier to recognize. This isn't true. As Dr. Forbes pointed out last year after the April super-outbreak, comparing tornadoes today to historical tornadoes isn't a fair comparison. Some strong tornadoes were likely rated higher than they would be today due to an improved understanding of the physics of tornado damage. Poorly constructed homes can demonstrate F5 damage in winds less than 150 mph. http://www.weather.c...er/8_24558.html "But it's also a "different world" in the way that tornadoes get rated. The mainstay of the original Fujita Scale used to rate tornadoes was that a home crushed into small pieces and blown away would earn an F5 rating, with wind speeds estimated at 261-318 mph. Engineers surveying the tornado damage back in 1974 began to tell meteorologists that it didn't take 300 mph winds to turn homes into piles of rubble and cast the pieces to the wind. Even well constructed concrete block and brick school buildings could fail in 220 mph winds, they said. And homes with damage apparently fitting an F5 description often happened because the house was not properly secured to its foundation in winds less than 150 mph. In the years since, these engineering analyses began to work their way into damage assessments, and in 2007 an Enhanced Fujita Scale (EF Scale) system was officially implemented. An EF5 tornado has winds estimated as low as 201 mph. And it's difficult to rate a tornado as EF5 based upon it just demolishing a house. Statistically, the number of tornadoes being rated 2-5 have been decreasing since the 1970s, despite the total number of tornadoes being recorded showing a dramatic increase. This is at least partly a consequence of the introduction of engineering concepts into the rating process. I was part of the team that developed the EF Scale, and it's a system that more accurately estimates tornado wind speeds. But it troubled me then (and still does) that it might be hard to compare past tornado outbreaks with future ones and determine which was worst. It's apples and oranges, to some extent, in the rating systems then and now." Link to comment Share on other sites More sharing options...
Entropy Posted July 31, 2012 Share Posted July 31, 2012 I'm not saying that the total number of tornadoes has or has not increased. But it's just not appropriate to say that the frequency of all tornadoes has decreased by extrapolating based on an apparent decrease in strong tornadoes without recognizing the uncertainties present in that data. Link to comment Share on other sites More sharing options...
Ellinwood Posted July 31, 2012 Share Posted July 31, 2012 This isn't true. As Dr. Forbes pointed out last year after the April super-outbreak, comparing tornadoes today to historical tornadoes isn't a fair comparison. Some strong tornadoes were likely rated higher than they would be today due to an improved understanding of the physics of tornado damage. Poorly constructed homes can demonstrate F5 damage in winds less than 150 mph. http://www.weather.c...er/8_24558.html I'm not saying that the total number of tornadoes has or has not increased. But it's just not appropriate to say that the frequency of all tornadoes has decreased by extrapolating based on an apparent decrease in strong tornadoes without recognizing the uncertainties present in that data. I agree that it's not a complete apples to apples comparison, but my argument is that even if you downgrade the F 4-5 tornadoes down by one (or even two if you're dealing with a F-5), they still fall within the intense/violent threshold (F/EF 3-5) and would not lower that overall count. To touch on your example of F5 damage getting reduced to winds of 150 mph or slightly less, an EF-3 has a bottom wind speed of 138 mph (on the derived scale), so it would still be within the intense/violent range of EF 3-5. Now if you can argue that there is a significant amount of F 3-5 tornadoes that would be classified below the 3-5 range using modern methodology, then yes the count would go down and I could see the newer methodology that incorporates construction having an effect on the overall numbers. But even then, if the argument stands that the number of intense/violent tornadoes is still going down after the implementation of the modern classification methods, then you really can rule out the new methodology as having an impact on the overall number. In regards to the second post, we're only talking about the stronger tornadoes, and not the frequency of all tornadoes. We are not using the frequency of strong tornadoes as a proxy for the frequency of all tornadoes. Link to comment Share on other sites More sharing options...
andyhb Posted July 31, 2012 Share Posted July 31, 2012 I still find it fascinating that we went so long without an F/EF5 from 1999 to 2007, although, that said, the argument can be made that few of the tornadoes in that timespan should've been rated higher (Girard/Franklin, KS on 5/4/03 and Harper, KS on 5/12/04 come to mind in particular). Link to comment Share on other sites More sharing options...
Buckeye05 Posted July 31, 2012 Share Posted July 31, 2012 I still find it fascinating that we went so long without an F/EF5 from 1999 to 2007, although, that said, the argument can be made that few of the tornadoes in that timespan should've been rated higher (Girard/Franklin, KS on 5/4/03 and Harper, KS on 5/12/04 come to mind in particular). I heard from a member on Stormtrack about the controversy surrounding Girard/Franklin. Apparently they guy that made the call said that he found "evidence of F5 damage" but decided that the damage was "overall F4 damage" taking the rest of the path into consideration. I forget the name of the surveyor, I think his last name was Douglass. I just remember people expressing skepticism about some of his calls/method of surveying. Not trying to nitpick on the guy personally, just saying the controversy about that tornado stems from that. The Harper damage was very extreme, but I think the reason they went with F4 was the lack of anchor bolting with that house. Link to comment Share on other sites More sharing options...
Ellinwood Posted July 31, 2012 Share Posted July 31, 2012 I would almost suggest moving the tornado discussion to a new thread, especially if people want to continue the original discussion... but if the original discussion's basically done, then whatevs Link to comment Share on other sites More sharing options...
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