National Geographic News
A survivor of a tornado in Moore, Oklahoma looks through her destroyed house.

Dana Ulepich searches inside her house ruined by a massive tornado in Moore, Oklahoma, on May 20.

Photograph by Brett Deering, Getty Images

Brian Clark Howard

National Geographic

Published May 21, 2013

A deadly tornado ripped through the Oklahoma City area on Monday, leaving 24 dead. As rescue crews assist victims, scientists have fanned out across the Great Plains, seeking to better understand how severe storms form, and how people may better guard against their worst impacts.

Joshua Wurman, director of the Center for Severe Weather Research in Boulder, Colorado, has spent the past several days in pursuit of tornadoes across Oklahoma. "It's been a very busy time," Wurman tells National Geographic.

And yet many people's thinking about tornadoes is shaped as much by folk wisdom passed down from their parents as it is by solid science. For example, one piece of folk wisdom has it that moving to the southwest corner of a basement or building reduces risk of injury during a tornado. There are no data to support that, Wurman says, noting that the important thing is to stay low and away from windows.

Wurman works with a team of scientists to position mobile instruments as close as possible to severe weather events. This includes Doppler on Wheels (DOW), a Doppler radar system mounted on a truck, and instruments called Tornado Pods, 3.3-feet-high (1-meter-high) towers that measure wind speed and direction. (Related: "A Tornado Chaser Talks About His Science and Craft.")

"By having the radar up close we can get much finer resolution," says Wurman. "It's like painting your finger at arm's length versus being across the parking lot. The goal is trying to understand better how tornadoes form, the 3-D structure of the winds, and how they do damage."

His work isn't all about the heart-pounding thrill of a storm chase: "Parts are very boring and tedious."

"We eat bad food and stay in mediocre hotels," he says. "We know gas stations and truck stops by heart, so that's not so fun. But what is fun is to learn things that have never been known before. Seeing inside a tornado with this level of detail for the first time ever is like seeing a new continent."

Wurman says that some popular thinking about tornadoes is out of date and could even be dangerous. He helped us assemble this list of five persistent tornado myths:

Myth #1: Tornadoes target trailer parks.

Tornadoes do not "seek out" trailer parks more than any other neighborhoods. Trailer parks "do have a lower threshold for being damaged," Wurman says, which has helped lead to more media attention on those areas.

Well-built framed houses can typically survive tornado-force winds of 120 miles per hour (193 kilometers per hour), Wurman says. But poorly built houses, and a lot of older mobile homes, can sustain significant damage at those speeds because they are weaker structures.

"I've seen that with hurricanes in Florida," Wurman says. "A trailer park was just devastated, but wood-framed homes nearby were pretty much OK, with just some minor roof damage, even though they saw the same winds."

He adds that much of the Midwest region known as Tornado Alley plays host to homes that were not built up to modern codes, largely because they are so rural that there aren't true codes or because owners couldn't afford to follow the rules.

Myth #2: During tornadoes, drivers should shelter under overpasses.

"That might not be such a good idea because wind could accelerate under the overpass," Wurman says.

And climbing an overpass is a definite no-no, since being up in the air could make someone more likely to get hit by windblown debris.

"Like a soldier dropping to the ground to get away from shrapnel, being low down is better because you are getting away from debris," Wurman says.

Myth #3: Opening windows reduces pressure and protects buildings.

"Houses don't explode because of the low pressure," Wurman says.

"Usually, debris breaks the windows, letting wind get in the house. It may seem like it exploded... but wind may have pushed the walls down or pushed the roof off," he says. "Opening the window lets the wind get in, which is the worst thing you could do."

Instead, Wurman suggests trying to keep wind out of the house with hurricane shutters.

Myth #4: Rivers, lakes, hills, and other local landscape features block tornadoes.

Wurman says terrain certainly affects the weather, noting that where he lives, in Boulder, Colorado, strong thunderstorms are rare because of the impact of the Rocky Mountains.

And he says that being downwind of an ocean or large lake tends to decrease the likelihood of a strong thunderstorm-and therefore tornadoes-because air tends to cool over bodies of water, reducing its energy.

But such factors are dependent on large-scale geography, as opposed to being determined at a micro level.

Myth #5: Large cities can't be hit by tornadoes.

This long-standing myth is perhaps less popular today, after recent years have seen tornado strikes in Atlanta and Salt Lake City. Wurman says there is some possibility that the urban heat island effect could strengthen thunderstorms downwind from dense cities.

He adds that smaller cities and suburbs tend to have more houses, versus large apartment buildings, which may give storms more opportunity to pick up debris and cause more damage.

"As far as what would happen if a tornado hit an urban canyon, like Manhattan, the effects are not well known," Wurman says. The geographic footprints of big city centers are relatively small, so the chances of direct strikes are not great.

0 comments

Share

Popular Stories

The Future of Food

See more food news, photos, and videos »