Science Behind Chasing Tornadoes

Around dinner hour on June 24, 2003, the entire hamlet of Manchester, South Dakota—walls and rooftops, sheds and fences, TVs, refrigerators, and leftover casseroles—lifts from the earth and disappears into a dark, thick, half-mile-wide (0.8-kilometer-wide) tornado. The pieces whirl high in the twister's 200-mile-an-hour (322 kilometer-an-hour) winds, like so much random debris swept clean from the landscape. A mile (1.6 kilometers) or so north of town 36-year-old Rex Geyer pulls the curtains back from the window of an upstairs bedroom and watches Manchester disappear. Rex stands frozen. The tornado seems to be standing still too, not moving one way or the other. It takes him a fearsome minute to realize what that means—that the deadly storm is coming straight for him. Just earlier, Rex had sat down to fried chicken with his wife, Lynette, who is eight months pregnant. "We had heard about some wicked tornadoes down in Woonsocket, where Lynette's from," he would say later. "We were keeping our eyes on the TV, and I was looking outside, and I said, 'Well, geez, it don't really look that bad.'" But now rain is pounding down, obscuring the monster storm bearing down on his two-story farmhouse. Rex's brother Dan, who lives up the road, charges into the house. "He almost rips the screen door off the hinges, and he's hollering, 'We gotta get into the basement!' But I just saw the Manchester debris and don't think we'll survive in the basement, so we pile into Dan's car."

"Should I turn the lights and the TV off?" Lynette asks. She hasn't seen the storm.

"No, no! We have to go now!" They leave everything but a mobile phone.

As they flee, two cars hurtle down a nearby dirt road in the opposite direction—straight at the tornado. Tim Samaras, a 45-year-old electronics engineer from Denver, and his storm-chasing partner, Pat Porter, are in a van that carries six probes, often called "turtles"—squat, 45-pound metal disks that look like flying saucers. Through embedded sensors, the probes can measure a tornado's wind speed and direction, barometric pressure, humidity, and temperature. Samaras's mission, and his passion, is to plant them in the path of the funnel. His hope is that both he and the instruments survive.

http://science.nationalgeographic.com/science/earth/earths-atmosphere/chasing-tornadoes-earth/