Word: tornadoes
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...simplest explanation is that tornadoes form when a smaller, even more rapidly rotating updraft descends from the mesocyclone like a vacuum cleaner's nozzle. To the eye, this is exactly what appears to be happening. But while scientists agree that the updraft is essential, many doubt that it provides the sole mechanism for tornado formation. Some scientists think the rapid sinking of colder, dryer air near the rear flank of the storm may be key. If this rush of air encounters wind shear on its way down, then it too will start to rotate. In this scenario, a tornado occurs...
...another possibility, says UCLA meteorologist Roger Wakimoto, is that the tornadoes typical of supercell storms are formed by the same mechanism that creates the smaller, less destructive funnel clouds known as waterspouts, landspouts and dust devils. These twisters all build their vortexes not from the clouds down but from the ground up. They are triggered, Wakimoto says, by low-lying eddies of air that are perturbed by a fast-moving front or some other local disturbance. When a supercell storm passes over such an area, swirling air near the ground could easily be sucked into the updraft and spun...
Until VORTEX, the competing hypotheses about tornado formation could not be rigorously tested. The downdraft theory, for example, was bolstered by storm chasers' sightings. Observes Erik Rasmussen, field coordinator for VORTEX: "What storm chasers see first is a big dark cloud, then a bright spiral slicing into the base." The problem is that the flow of air within a big storm is so complex that what the eye sees cannot always be trusted. Hence the need for measurements...
...wind, they believe, must be subject to Ockham's razor, a principle first stated by 14th century philosopher William of Ockham. According to this principle, the theories most likely to prove true are those shorn of unnecessary embellishments. But, says Texas A&M meteorologist Louis Wicker, the process of tornado formation now looks more complicated than ever. In fact, the more VORTEX data sets he feeds into his computer models, the more convinced he is that there could be several ways to make a tornado. "Nature," he laughs, "has kicked us in the pants...
...then tornadoes have long been known for their capricious behavior. The same twists of wind that can derail trains and rip up pavement can be surprisingly gentle. Says National Weather Service meteorologist Donald Burgess: "I've seen a phonograph record driven through a telephone pole, and the record wasn't broken. I've seen a fridge thrown several hundred yards, while glasses on a nearby table weren't touched." Last month Betty Lou Pearce, a 64-year-old clerk from Pilot, North Carolina, hid from a tornado in her bathtub and moments later found herself sliding into the woods...