It's a combination of the Gulf of Mexico, the desert Southwest, and strong storm systems that makes the U.S. Midwest so prone to tornadoes.
Bill Paxton and Helen Hunt played storm chasers in Twister, the 1996 blockbuster. But the real life of a storm chaser is quite different from the movies. A typical day means hundreds of miles of driving. This season, Samaras logged 25,000 miles (40,000 kilometers).
Most of the time, he never sees a tornado. Scientists still don't know exactly why some severe storms develop tornadoes, while others don't.
"It's one of the biggest mysteries left in our understanding of the atmosphere," said Samaras.
When he finds a promising storm, Samaras becomes entirely focused on the chase, double-checking the forecast, scanning the data, and watching the sky. "There's only one shot at being at the right spot, and I want to be there," he said.
If a tornado develops, he must predict the right coordinates, put himself in the path of the tornado, deploy the probe, and get out of the way as fast as he can. On average, he gets the location right about two out of seven outings.
Samaras developed the state-of-the-art probes at Applied Research Associates, the Denver-based company where he works as an electrical engineer. Known as a "turtle" in meteorological circles, the probe is a squat, conical 45-pound (20-kilogram) device, 20 inches (51 centimeters) across, six inches (15 centimeters) high, and crammed full of sensors. Unlike older models, it can measure humidity, pressure, temperature, wind speed and the tornado's direction.
"It's a complete weather station," said Samaras. "Having the barometric pressure drop within a tornado helps us understand the structure of tornadoes and the associated windfield. It provides a piece of the puzzle to help solve the mystery of tornadoes, their violent behavior, and the damage they leave."
With more data from a range of tornadoes, the measurements may prove useful for predicting the intensity and duration of future tornadoes.
"We currently have about an 80 percent false alarm rate when it comes to predicting which storms will spawn tornadoes," Paul Markowski, a professor of meteorology at Penn State University in University Park, said in a prior interview with National Geographic News. "All research we do is directed at reducing that rate. Tim's work is a step in the right direction."
Samaras believes the data set collected during the Manchester tornado will prove invaluable. He is amazed that his probe actually stayed on the ground as the violent twister passed over it.
As the team retreated north from the tornado, National Geographic photographer Carsten Peter deployed a custom-built camera probe directly in the path of the destructive tornado. Later, the remains of that probe were retrieved 450 feet (140 meters) away. All its glass ports were smashed and the camera inside was ruined.
Tornadoes are classified on what's known as the F-scale, which runs from F-0 to F-5 and measures the damage left behind. An F-0 tornado, with winds up to 73 miles per hour (117 kilometers per hour), generally cause minimal damage, while an F-5 twister has winds exceeding 300 miles per hour (482 kilometers per hour).
The Manchester, South Dakota, tornado was rated F-4 with winds estimated at 260 miles per hour (420 kilometers per hour). To Samaras, it certainly was the highlight of this tornado season.
"It was the closest that I have ever been to a violent tornado," he said. "I have no desire to be that close again."
Additional reporting supplied by Bijal P. Trivedi.
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