for National Geographic News
In his 15 years as a storm chaser, Tim Samaras had never seen a tornado this close. The thundering twister was heading straight for him. "It looked like a barrel," he said. "It was half a mile [0.8 kilometer] wide."
He jumped out of his Dodge Caravan to drop special instrumented probes into the path of the oncoming tornado. But what if the car got stuck in the mud?
"We had debris flying overhead, and we could watch the telephone poles get ripped out of the ground and absorbed into the tornado vortex," he said.
It took Samaras only six seconds to deploy the probe.
Then he yelled to the driver to hit the gas. As they sped off, they could see the twister sweeping over the probea direct hit. The tornado chased them down the road, then veered away.
When Samaras returned, he found the probe intact. It registered an astounding 100 millibars, the biggest pressure drop ever recorded in a tornado. A two-story farmhouse 40 feet (12 meters) away had been destroyed. The community of Manchester, South Dakota, lay in ruins.
The dramatic story is part of the National Geographic Ultimate Explorer documentary "Inside the Tornado," which airs on MSNBC this Sunday, July 27, at 8 p.m. ET/PT.
Every May and June, Samaras, whose research is supported by the National Geographic Society Committee for Research and Exploration, speeds around America's "Tornado Alley"a broad swath of land between the Rockies and the Mississippi, where tornadoes are most frequentin a Dodge Caravan outfitted with GPS, radios, scanners, wireless Internet, and satellite tracking devices.
He's looking for supercells, violent and rotating thunderstorms that, fed by strong winds in the upper atmosphere, last for several hours. These storms provide very heavy rain, frequent lightning, huge hail, andsometimestornadoes.
Samaras uses the Internet to gather information on storms, relying on surface data, upper level winds, sounds, satellites and radar. False alarms are common. Doppler radar can tell the National Weather Service that a tornado is likely, but it's the storm spotter in the field who must validate the warning.
"We look for a lot of moisture, strong upper level winds that are turning in different directions in the atmosphere, strong instability, and some sort of lifting mechanism for the actual development of thunderstorms," he said. "All of them must be present at precisely the right time."
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