The enhanced F-scale takes effect February 2006.

[Greg Stumpf]

Originally posted by Stuart Robinson
As can be seen that the new EF-Scale increments are also not equal and therefore scientifically flawed from the word go!

Why must the scale be linear to not be flawed?

 

[Jeff Snyder]

Originally posted by Stuart Robinson

** Note winds in the Moore 1999 tornado were measured by Doppler at 318mph

Just as an update... Dr. Wurman mentioned in his stormchase chat last year that it's more like 301mph +/- 17mph. There are statistical assumptions and approximations inherent to radar signal processing, so one should never be 100% confident that velocity (and reflectivity for that matter) from any particular range bin are exactly true, thus the likely reason it was changed from 318mph to a range.

 

[rdale]

"Why must the scale be linear to not be flawed?"

The hurricane scale wind breakdowns are not linear either...

 

[Jason A.C. Brock]

If this is the case they should remove Fujitas name from the scale.

 

[rdale]

If what is the case? He always knew (and expected) it would be refined with time...

 

[Bill Tabor]

Ok, just read the entire 95 page PDF and then skimmed it back and forth a few times so I have a pretty good handle on it.

Torns won't be re-rated. EF-scale correlates to F scale but with different wind ranges. Biggest problem I see is even though their method was systematic and scientific they used an expert classification system as wind speed determination similar to the old Fujita scale. This can mean garbage in = garbage out at least in estimating accurate wind speed ranges to predict a damage level simply because (as they mention in the paper) that research hasn't been done either deterministically or experimentally using modeling. They do reference that some studies of the past have suggested that F-scale ratings can be higher than needed to cause the actual damage. If the goal is to accurately represent wind speed that caused this damge then EF is somewhat inadaquate. As a way to further quantify and define F-scale so it can be better applied and compared to various damage cases then EF should work well.

I also see there may be a problem integrating actual windspeed / damage scenarios (such as those measured by DOW) to EF if those initial expert wind speed estimates were very far off.

It may be harder to get a higher rating in EF than F because the specificity based on building materials and construction is implied whereas in F scale it was arbitrary and hard to determine. Note also that top ranges of F-scale were not used only the median values to equate to EF ranges.

All that said, it may still be a very useful improvement for future database research efforts and insurance appraisal purposes as well. On the other hand it doesn't sound as macho because now when we see a tornado later ranked EF5 it's speed may only be suggested as > 200mph as opposed to maybe 318 mph winds to cause that damage.

So :lol: from the chaser perspective this is going the wrong way. Instead EF should have upper range at the Mach level. That way we could really boast of something during after chase parties while sitting around drinking beer :wink: .

 

[Perry Williams]

I've believed for years that any tornado possessing wind speeds of 200 mph or greater should be categorized as "violent"; as we know from past tornadoes and hurricane Andrew's peak gusts, few structures will withstand 200 mph winds.....and tornadoes of this intensity are capable of taking many lives, especially if they strike a mobile home community or RV park (i.e.- Evansville, IN 11/05; Camilla, GA 2/14/00; Kissimmee and near Orlando, FL 2/23/98 ).

Over the years, I've spoken or corresponded with several meteorologists who were involved with the 1974 "superoutbreak"; either as forecasters on duty or as part of post tornado surveys (incl a couple who were with Dr Fujita when assessing Alabama tornado damage), and none of them believe wind speeds at GROUND level reached 300 mph. I'm not foolish enough to state a maxi tornado's peak winds couldn't reach 300 mph, but in my years of experience and research, even if they were......we'd have difficulty determining it (because once you reach 225-250 mph, virtually everything is obliterated; even most well built homes completely leveled and swept away from their foundations).

At age 44, I'm old enough to remember school encyclopedia and even weather books which estimated tornado wind speeds at 500-600...or even 800 mph. In those same encyclopedias and weather books, there was speculation it took such unbelievable winds to "defeather" chickens and blow automobiles hundreds of yards. We now know that was incorrect; that such incredible phenomena can occur at much lower wind speeds. As someone else mentioned, the National Hurricane Center catergorizes a hurricane as cat-5 once sustained wind speeds reach 156 mph, no matter how high they go (IMO the infamous 1935 Labor Day hurricane may have possessed 190-200 mph sustained winds with peak gusts possibly exceeding 230 mph;, based on the gruesome aftermath and exceedingly small diameter of eyewall and max winds/ pressure gradient; about the same size as 2004's Charley at landfall on SW Florida....except the central pressure of the Labor Day hurricane was about 50 millibars lower :shock:

This new enhanced rating scale does the same.....once a tornado is judged to have reached 200 mph wind speeds, it will be recorded as a F5...no matter whether it peaks at 200 or reaches the upper limit possible (IMO 250-275 mph in rare cases [i.e.- Xenia, OH & Guin, AL on 4/03/74).