Storm Chaser Drives to Extremes to Probe Tornadoes
for National Geographic News
|July 25, 2003|
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."
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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