As someone who has led or assisted on several surveys, I think that as we have learned more about the myriad variables affecting tornado damage intensity, we HAVE tightened things up a bit. I would say this is exactly what we need to do, although I believe one could make the case that in some instances it has been a little too tight. This is only natural, however, and will eventually work itself out. The biggest problem will be recognizing what is likely a vast tendency to overestimate tornado strength early in the climatological database. Any tendency to underestimate at this point is likely much smaller than the earlier tendency to overestimate, especially in regards to retroactive ratings made by photograph alone.
We have, I believe, improved the credibility of damage ratings through learning to take in the "big picture," so to speak. I rated the Shelby County, Indiana tornado earlier this month. Along the path was a farmhouse which had been blown off the foundation. However, after further examination, the foundation was loosely stacked stone, and little evidence could be found of attachment of the home itself to the foundation, beyond straight nails. Also, right next to the front steps were two large trees, with the majority of their trunks still standing. Now, in 1975, perhaps this would have been rated F5. Given what we know now, though, we could go no higher than strong F3. This was of some consternation to one gentleman who emailed us later, arguing that F5 was the most appropriate rating based on his literal reading of the scale's descriptions. After some exchange, he agreed that F5 was unrealistic, but still maintained that strong F3 was too low. I guess if we wanted to simplify things, we could simply rate the damage and only the damage and make only tenuous connections to the strength of the causative tornado, but I think few would argue that this is of any use. I remain interested to see where the EF scale efforts will lead us.
Also, I think we can all agree that as applied today an F6 tornado is impossible. It will require a redefinition of our application to happen, and the damage would have to be absolutely unprecedented in scale and scope.
p.s. At least we'll know that any potential future F-4's and F-5's will truly deserve being rated as such.
