The F5: Mother Nature's Massive Twist of Fate

You can't determine that a tornado is an F5 -- the most violent ever seen -- by directly calculating its wind speed. Wind measuring devices fly to pieces at half the violence of a 300 mph storm.

You measure it by the destruction it leaves. The splinters and shards and how far away they land. The late Tetsuya "Ted" Fujita -- who devised the Fujita tornado scale, in which an F4 is "devastating" but an F5 is "incredible" -- first got interested in this force in the '40s.

After he had visited Nagasaki and Hiroshima.

There are 22 references to "whirlwinds" in the Bible. The highest number is in the Book of Job.

Fewer than 1 percent of all tornadoes pack the terror of an F4 or an F5. Those, however, produce 67 percent of the deaths, according to the Tornado Project, a company that collects tornado information.

The classic definition of an F5 involves strong frame houses being lifted off their foundations and carried considerable distances to disintegrate; steel reinforced concrete structures being damaged; the bark being ripped off trees. One particularly unsettling part is the automobile-size missiles flying through the air.

The capriciousness of tornadoes adds to their mystique. One Moore, Okla., woman who'd been hiding from an F5 in her bathroom discovered she had a clear view of the calm eye of the tornado because the roof had come off, recalls Daniel McCarthy, warning coordination meteorologist at the National Weather Service's Storm Prediction Center in Oklahoma.

When it finally passed, she found some walls were also gone. Her dining room hutch, however, was almost untouched. Except for the teacups. They had been turned upside down, though not broken.

Tornadoes sneak up on you. Hurricanes give you days to evacuate. Tornadoes drop out of storm systems like bombs. You're lucky to get 11 1/2 minutes' warning, which was the National Weather Service average last year. La Plata got about eight minutes' warning.

Their power is almost unimaginable. The last F5, which hit Oklahoma on May 3, 1999, packed the highest winds ever found near Earth's surface, according to Doppler on wheels, the new truck-mounted portable radar technology that is just beginning to look into the heart of such storms from fairly close up. The winds of that F5 hit something like 319 mph.

They are like a giant blender, says Timothy Tonge, a forecaster with the company that runs F5 Tornado Chasing Safaris, which gets tourists up close and personal with twisters. "It's not so much the 300 mile per hour winds," he says. "It's all the debris in it that pummels you at 300 miles per hour. It's like a big shredder."

People disagree on what a tornado sounds like. Many discount the notion that they sound like a freight train. They compare it more to being behind a 747 at full-throttle takeoff, or standing at the bottom of Niagara Falls.

Tornadoes are frequently described as impenetrably dark, like a black hole absorbing all light, showing only flashes of debris. But that's because the storms that create them can tower 10 miles high, blocking out the sun, not to mention dumping all that rain. When you're standing in front of a tornado, it can be brilliantly backlit by the setting sun in the clear sky behind it, giving it a dark gray or deep blue cast. If you're standing behind it, it frequently seems light gray or white. If hail is associated with it, it can have a green tone.

Tornadoes are exciting if they don't hurt anybody.