National Geographic Today
Tuesday night Tim Samaras stood his ground in front of the quarter-mile-wide (400-meter-wide) tornado that would level part of the tiny town of Manchester, South Dakota, When the whirling vortex was only about 100 yards (90 meters) away, he jumped out of his van, dropped a scientific probe next to the road and yelled to his driver to make a swift getaway.
Eighty seconds later the tornado swept over the probe. "It was a direct hit! We haven't slept all night," Samaras says. "This is a historic occasion. But we were definitely too close."
Samaras is a professional storm chaser, which means he spends May and June speeding around Tornado Alleya broad swath of land in the central United States between the Rockies and the Mississippi, where tornadoes are most frequentin a Dodge Caravan outfitted with GPS, radios, scanners, monitors, a wireless Internet connection and satellite tracking instruments.
His harrowing task: to spot tornadoes, try to put himself in their path and then deploy the newly designed probe that will measure humidity, temperature, pressure, wind speed and direction in the vortex of the beast. Then he promptly gets out of the way.
On that Tuesday night, Samaras achieved his most significant feat yet: The probe he helped design measured the biggest pressure drop100 millibarsever recorded in the heart of a tornado.
"This is one of the best measurements ever made," says Erik Rasmussen, a meteorologist with the National Severe Storms Laboratory, based in Norman, Oklahoma. "The data collected will be a gold mine."
"I've been a passionate storm chaser for 15 years," Samaras says, "and this is an opportunity to combine my hobby and professional work." Samaras is an electrical engineer at Applied Research Associates, Inc., based in Denver, Colorado, where he co-designed and built the probe, known as a "turtle" in meteorological circles.
The squat, conical 45-pound (20 kilograms) device is 20 inches (50 centimeters) across, six inches high and crammed full of sensors. Its development was funded by the Department of Commerce. The National Geographic Society supported its use in the field with a grant from the Committee for Research and Exploration.
Even with the most sophisticated weather equipment, tornadoes are tough to spot, because they're too small to be seen by National Weather Service Doppler radar or satellite images. So Samaras looks for supercells, the most dangerous kind of thunderstorm and the most likely to spawn tornadoes.
Supercells are huge, rotating cloud masses 60,000 feet (18,300 meters) tall, and can extend a couple of miles across. "Structurally they are like huge spinning soup cans," says Paul Markowski, a professor of meteorology at Penn State University in University Park. If a portion of this swirling cloud mass touches the ground, a tornado is imminentso when storm chasers like Samaras see that conditions are ripe for supercell formation, the chase begins.
Right Place, Right Time
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