Wednesday, February 15, 2006

Went to the Tulsa Skywarn program last weekend. I do enjoy the presentations they put on. One discussion in particular has me thinking; the new enhanced F-scale.
I like the idea behind it, but I think the final product is lacking. I need to look into it a little more, but some aspects of it seem way off.
One of the supposed purposes of the new scale is to allow for more accurate ratings in areas where the old common indicators (houses) were lacking, thus the new list of 28 indicators, including trees. So now we can have a rated tornado when it goes over open country (assuming trees are present). The max rating for hardwood tree damage would be F3, or around 147 mph. This is better than the old damage based rating of F0, regardless of actual wind speed.
However, if I understand it correctly, F5 damage can't be determined in a residential area, because according to the new scale, the upper threshold winds required for total destruction of a house (nothing but ruble), are just below the wind speed in an F5 tornado (now 200 mph).
Here's what I'm getting at: that while ratings will improve in open country, they will not improve on the higher end, as in the residential setting case. In order to rate a tornado a definitive F5, it would have to directly hit the likes of a shopping mall, medium or high rise building, or an institutional building. In other words, the May 3, 1999 Moore tornado with measured winds of 316 mph would have likely officially been recorded as an F4 (even if we are conservative with the measured speed and say 300 mph, something is still wrong).
Granted, the original F-scale wasn't very accurate at higher wind speeds, but I don't think this is an improvement. I think more needs to be done to accurately survey damage from large tornados that (increasingly) have measured wind speeds, to derive more accurate indicators for higher speeds.
Because of lack of time and funding, I feel the new Enhanced F-scale turned out to be experts' best guesses at more "accurate" wind speed damage indicators. I also feel that there should have been more public discussion and debate about the shortcomings of this new scale.
If, as I find out more, I discover my interpretations to be wrong, I will bring it up here.

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