Twisted chase: two daredevils hunt down tornadoes to find out more about these super-fierce storms.

A car is one of the worst places to be during a tornado. Swirling winds can reach more than 480 kilometers (298 miles) per hour. That's powerful enough to toss even the largest vehicle like a little toy. Knowing this, it might be hard to believe that anyone would intentionally try to drive a car inside a twister. But that's exactly what two daredevils plan to attempt this spring. Sean Casey and Steve Green have souped-up cars they will use to chase the spiraling storms through "Tornado Alley" (see map, above). This band of land in the U.S. has more tornadoes per year than anywhere else in the world. Each man is on his own mission, but their goals are the same: Both drivers are hoping to capture video footage and scientific data from inside a tornado.

BREWING STORMS

Tornadoes regularly whirl through Tornado Alley because of the region's unique geographic features. Tornadoes are a type of cyclone with inward spiraling winds that rotate. These storms occur when warm, moist air from the Gulf of Mexico forms thunderstorms near and under the jet stream, an air mass traveling eastward. As moist air rises in thunderstorms, it cools and the water vapor condenses into clouds, rain, and hail, releasing extreme amounts of energy. The jet stream's strong eastward current adds spin to the storm (see Nuts & Bolts, left).

As of this February, a new scale is ranking the intensity of these whirling storms. The Enhanced Fujita Scale replaces the Fujita Scale, which had been used since 1971. Both scales show the relationship between a tornado's wind speed and how much damage it causes to structures. However, the Enhanced Fujita Scale allows better estimates of this damage. That's because it considers building materials and engineering methods when calculating structural damage (see That Was Intense, p. 13). For instance, an EF-0 tornado can rip down tree branches. An EF-5 can turn a house to splinters. Green and Casey both hope to enter a mid-level strength tornado. Green hopes to enter an EF-2.

TORNADO TRACKERS

Green is a former NASCAR race-car driver. He has survived his share of car accidents during races, but driving his Tornado Attack Vehicle or TA-1 into a tornado is a different story. "On a racetrack, there are only so many things that can happen," says Green. "In a tornado, you don't know what's going to happen. You know, I've seen cows fly."

Casey is an IMAX filmmaker who is collaborating with scientists to help them learn more about the behavior of tornadoes. He hopes to capture the turbulent images on his camera, which is mounted to his homemade Tornado Intercept Vehicle (TIV).

Both Casey and Green have designed their cars with safety and science in mind. The cars are armored with strong metal plates and shatterproof windows. The shielding protects the drivers from flying debris and weighs down the cars in strong winds. Casey's TIV weighs more than 6,000 kilograms (13,227 pounds) and Green's TA-1 tips the scales at 3,628 kilograms (8,000 pounds).

Green enlisted the help of engineers from his NASCAR days to redesign a race vehicle for tornado chasing. He even wears protective gear similar to that worn by NASCAR drivers, like a flame-resistant suit and a crash helmet.

Both cars have a hydraulic system that lowers the body of the vehicle to the ground. Any space between the car and the ground may allow the extreme winds to get underneath the vehicle, causing it to topple over or get tossed through the air. Inside, the cars are equipped with various sensors to record scientific data.

"I want to make the ultimate IMAX film [on tornadoes]," says Casey, "and at the same time help the [tornado scientists] learn about what goes on inside a tornado."

STORMY SCIENCE

While Green has not officially paired with a scientific institution, Casey has teamed up with Josh Wurman, the head of the Center for Severe Weather Research in Boulder, Colorado. Wurman scans the skies for tornado activity using a device called "Doppler On Wheels (DOW)." This instrument looks like a big satellite dish sitting on the back of a flatbed truck. It uses radar to measure precipitation and the wind conditions that favor tornado formation, and maps the winds inside tornadoes.

Wurman parks the radar truck near a storm and uses a two-way radio and Global Positioning System (GPS)-aided vehicle tracking systems to navigate Casey to the tornadoes. "The hardest part of tornado chasing is finding a tornado and being in its path when it touches down," says Casey, who has been hunting tornadoes since 1999.

Wurman has equipped Casey's TIV with several meteorological devices for recording characteristics of weather. These instruments include a barometer to measure air pressure, anemometers to measure wind speed and direction, and a thermometer to measure the temperature inside a tornado.

Knowing the air pressure in a tornado tells scientists how much force the air exerts. Gathering information about the speed and direction of a tornado's winds tells scientists about the behavior of a tornado as it spins. Warm air fuels a tornado, so collecting information about the tornado's temperature may tell researchers how heat influences a tornado's severity.

Scientists have used radar to get information about the top and middle sections of tornadoes, but very little information about the ground level exists. Wurman is hoping that Casey's TIV will help him find out what is happening in the bottom 10 to 15 meters (33 to 49 feet) of a tornado.

This type of information--whether from Casey or Green--could help people design buildings that are better protected from the devastating force of a tornado, says Wurman.

nuts & bolts

A tornado is a violently rotating column of air that is in contact with both the ground and a cloud base. The most intense tornadoes can destroy anything in their paths. Although scientists are still gathering information about tornadoes, this is how they believe the fierce storms form.

1. FRONTS COLLIDE: Tornadoes form inside of huge thunderstorms called supercells. A supercell begins to take shape on the edge of two colliding weather fronts. There a cool, dry air mass above meets a warm, humid air mass below.

2. WINDY: The mixing of the two fronts along with powerful jet stream currents create wind shear. As the winds abruptly change direction or speed, a layer of air between the fronts starts rotating.

3. FUNNEL CLOUD: An updraft of rising warm air pushes the rotating column of air into a vertical column, or mesocyoclone. As the updraft cools, water vapor within intensifies the storm clouds.

4. TOUCHDOWN: Scientists believe downdrafts of cool air pull the mesocyclone toward the ground. At the same time, updrafts stretch the spinning column, speeding it up into a violent tornado.

For tips on staying safe during a tornado, visit: www.nssl.noaa.gov/edu/safety/tornadoguide.html

PRE-READIN6 PROMPTS

Jump-start your lesson with these pre-reading questions:

* Some states in the U.S. experience fewer tornadoes than others. Here are the states with the lowest incidences of tornadoes, along with the total number of tornadoes each of the states endured between 1950 and 2004: Alaska (2), Rhode Island (9), and Hawaii (31). Which states in the U.S. are hardest hit by tornadoes? Why?

* Tornadoes can move in any direction, but most tornadoes move from southwest to northeast. These whirlwinds can last from several seconds to more than an hour, but most tornadoes last under 10 minutes. Although scientists have learned a lot about tornadoes, there is far more that they are trying to find out. What are some things that they're hoping to discover?

CRITICAL THINKING:

* Tornadoes are dangerous. In 2006, 66 people died because of tornadoes. Despite this fact, Steven Green and Sean Casey are determined to continue chasing tornadoes with their souped-up cars. Can you think of some ways that will allow a person to safely study a tornado up close?

CROSS-CURRICULAR CONNECTIONS:

PERFORMING ARTS: Divide students into groups. Each group will take on the role of a TV news team preparing a special broadcast on tornadoes. Have the teams do research on how tornadoes form and how people should protect themselves in the event of an oncoming twister. Each team will then use the researched information to write a 3-minute news program and present it to the class. If video equipment is available, film the presentations.

RESOURCES

* For more on Steven Green, read "The Tornado Rider," by Charles Graber, Wired, October 2005. You can find the article online at: www.wired.com/wired/archive/13.10/tornado.html? pg=1&topic=tornado&topic_set=

* Tornado Intercept is a documentary created by the National Geographic Channel that follows Sean Casey as he plunges his car into tornadoes. You can watch a clip of the film or purchase a DVD copy at: http://channel.nationalgeographic.com/channel/twistedsunday/index.html

* To read personal stories from kids who have survived tornadoes, visit this Web site from the Federal Emergency Management Agency: www.fema.gov/kids/tornado.htm

* This Web site is filled with answers to some of the most frequently asked questions about tornadoes: www.spc.noaa.gov/faq/tornado/

DIRECTIONS: Fill in the blanks to complete the following sentences.

1.--is a band of land in the U.S. that has more tornadoes per year than anywhere else in the--.

2. Tornadoes occur when warm, moist air from the--forms thunderstrms near and under the--, an air mass traveling eastward.

3. As moist air--in thunderstorms, it cools, and the water vapor--into clouds, rain, and hail.

4. An--is an instrument used to measure wind speed and direction. A--is used to measure air pressure.

5. The Enhanced Fujita Scale is used to measure the--of a tornado. The scale shows the relationship between a tornado's--and how much damage it causes to structures.

ANSWERS

1. Tornado Alley, world

2. Gulf of Mexico, jet stream

3. rises, condenses

4. anemometer; barometer

5. intensity; wind speed

THAT WAS
INTENSE

The Fujita Scale was developed
in 1971 to measure
tornado intensity. Beginning
February 1, 2007, scientists now
use the Enhanced Fujita Scale.

Scale   Fujita    Enhanced   Damage
(F or   Scale     Fujita     to
EF)     Wind      Wind       Buildings
        Speeds    Speeds
        (mph)     (mph)

0       <73       65-85      Light
1       73-112    86-110     Moderate
2       113-157   111-135    Considerable
3       158-206   136-165    Severe
4       207-260   166-200    Devastating
5       261-318   >200       Incredible

SOURCE: NOAA STORM PREDICTION CENTER