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Tim Samaras, Severe-Storms Researcher, National Geographic Emerging Explorer

As families scramble to avoid deadly tornadoes, Tim Samaras races straight toward them. He careens across the United States' notorious Tornado Alley on a mission: Predict the exact coordinates of an unborn tornado, arrive before it does, and place a weather-measurement probe directly in the twister's violent, swirling path. "Data from the probes helps us understand tornado dynamics and how they form. With that piece of the puzzle we can make more precise forecasts and ultimately give people earlier warnings," Samaras explains. Since current warnings average a slim 13 minutes, every extra second of warning can be a lifesaver for residents facing a twister's wrath.

"It all started when I was about six years old and saw that fantastic tornado in The Wizard of Oz, Samaras says. About 20 years ago he began storm chasing. Now he spends every May and June putting 25,000 miles (40,000 kilometers) on his vehicle, chasing zigzagging tornadoes across the Plains. "About five years ago, as an engineer," he noted, "I designed the next generation of probe to measure pressure drops inside tornadoes." A history-making instrument, Samaras's "turtle" probe has recorded record-breaking drops in pressure—the condition that triggers a tornado's extreme wind speeds. "This information is especially crucial, because it provides data about the lowest 10 meters [33 feet] of a tornado, where houses, vehicles, and people are." His car jammed with GPS gear, radios, scanners, a wireless Internet connection, and satellite tracking devices, Samaras constantly checks the forecast, data, and sky. "I only have one shot at being at the right spot," he says. "The worst is being five minutes late. One traffic jam or detour and you can miss the whole show. That's why we try to anticipate the action and arrive while there's still nothing but blue sky. The storms develop right over our heads, and we follow them as they form." Often the fury fizzles. Tornadoes develop from only two out of every ten storms Samaras follows. And deploying a probe is only possible during two out of every ten tornadoes. "The odds are really against us," he admitted. "Storm chasing is probably the most frustrating thing one can do."

But then there are days like June 24, 2003. On a sleepy country road near Manchester, South Dakota, a half-mile-wide (0.8-kilometer-wide) F4 tornado dropped from the sky and barreled across the landscape with more than 200-mile-an-hour (322-kilometer-an-hour) winds. At precisely the right place and time, Samaras deployed three probes, the last one placed as he leapt from his car a mere 100 yards (91 meters) ahead of the approaching tornado. Sixty seconds later the tornado crossed that exact spot, full force. "That's the closest I've been to a violent tornado, and I have no desire to ever be that close again," he recalled. "The rumble rattled the whole countryside, like a waterfall powered by a jet engine. Debris was flying overhead, telephone poles were snapped and flung 300 yards (274 meters) through the air, roads ripped from the ground, and the town of Manchester literally sucked into the clouds. You could see the tornado's path perfectly carved through a cornfield where, like a giant harvester, it had mowed stalks down to the ground." Amazingly, his probe survived the tornado's direct hit, unmoved from the spot where it had been deployed. Thanks to the pyramid shape Samaras designed, wind actually pushes the probe into the ground, helping to hold the device in place.

A 6-inch-high (15-centimeter-high) weather station encased in steel, the probe has sensors that measure humidity, pressure, temperature, wind speed, and direction. "When I downloaded the probe's data into my computer, it was astounding to see a barometric pressure drop of a hundred millibars at the tornado's center. That's the biggest drop ever recorded—like stepping into an elevator and hurtling up 1,000 feet [305 meters] in ten seconds."

Every storm is different. Some require deploying probes as baseball-size hail falls. In another instance Samaras watched telephone poles fall in front of him, sending arcs of sparks exploding across the road as he made his escape. Yet another tornado developed at night, only allowing glimpses of its oncoming path during flashes of lightning. "My passion for storm chasing has always been driven by the beautiful and powerful storms displayed in the heartland each spring."

Video - Storm Chasers - Season Finale - Tim's Probe Intercept: http://www.youtube.com/watch?v=56nh_Awr7po