Q: Was the Bridge Creek/Moore/OKC area tornado on May 3, 1999, rated F6?
A: No. The tornado has been rated F5 (minimal F5, in fact), and will not be "upgraded" to F6.
There was some speculation in the media of an F6 rating after "Doppler on Wheels" (DOW) researchers announced that their radar measured 318-mph winds in the tornado while it was near Bridge Creek. However, the jump in reasoning to rating this tornado F6 can not be made, for many reasons:
Q: Was the May 3 tornado the strongest, most violent tornado ever?:
A: Probably not, but we really have no way of knowing. It is impossible to make direct, objective comparisons between the May 3 tornado and most other violent tornadoes of the past. Factors such as inflation, varying population and property density over time and space, and the lack of direct wind speed measurements from all but a very few other tornadoes, prevent such comparisons.
We do know that other tornadoes have been wider, many have been more deadly, some have been longer lived, and many have produced longer damage tracks. So the May 3 tornado was *not* the "biggest" tornado. Nor was it the widest, the deadliest, the longest lived, or the longest track tornado on record.
The May 3 tornado currently is the most expensive tornado ever recorded. The damage estimate (roughly $1 billion) exceeds that of all other past tornadoes, even when inflation is taken into account. If we adjust our damage figures from other violent tornadoes in the past to account for inflation, we find that several (Lubbock,TX - May 11, 1970; Omaha, NE - May 6, 1975; Wichita Falls, TX - April 10, 1979, to name a few) were very close to the May 3 tornado in terms of dollar amount of damage. But to make such comparisons truly representative, we must also account for population growth, and the fact that people generally own more today than they used to. (So not only is property worth more today, but there also is more of it.) It's impossible to adjust for these factors objectively, and hard to even estimate their impact. But efforts to account for these factors suggest that the May 3 tornado probably was *not* the most damaging, at least in terms of material losses.
The May 3 tornado likely does have the highest recorded tornado wind speeds. But since typical wind measuring equipment does not survive a strong tornado, there are about three dozen tornadoes on record from which wind speeds have been obtained. Those measurements usually have been obtained from special research projects, such as the Doppler on Wheels (DOW) project, and have been obtained from only a dozen or so tornadoes (less than 0.1 percent of all tornadoes). So while the DOW data indicate the highest *recorded* tornado wind speed, there have been tens of thousands of tornadoes throughout history for which no wind speeds were ever obtained. Some of them easily could have had stronger winds than the May 3 tornado.
Without wind measurements, tornado wind speeds can only be estimated by examining the damage that was done. If we compare damage caused by the May 3 tornado with that of other tornadoes in the past, we find that several other F5 tornadoes have produced damage comparable to, or even more severe than, the May 3 tornado. Some famous examples of other F5 tornadoes that produced comparable or worse damage - and therefore may have been stronger than the May 3 tornado - include the "Tri-state" Tornado of March 18, 1925, the Woodward, OK tornado of April 9, 1947, the Xenia, OH tornado of April 3, 1974, and the Andover, KS tornado of April 26, 1991.
It's also important to know that although the tornado was rated F5, very few areas affected by this tornado actually experienced F5 damage. There were only a few small, narrow areas near the center of the damage path where intermittent F5 damage was found: in the Bridge Creek area (Grady County), and in a few parts of south Oklahoma City and Moore (Cleveland County). This is less than 1 percent of the approximately 15 square miles of damage that this tornado produced. The maximum damage in Oklahoma and McClain Counties was rated F4 (which, of course, is still very devastating damage).