Tornado in a box

Teaching Pre K-8, Apr 2003 by Cowens, John

This activity for grades 3-8 can show students the cause of these powerful storms - with none of the devastating effects

As a teenager in Indiana, I thought it was exciting to sneak out of the house during tornado warnings and drive toward the storm in the hope of seeing the deadly and destructive funnel. When I finally did see a tornado, however, I packed my bags and moved to a state where severe storms are very rare - Oregon.

Tornado facts

A tornado is a violent storm accompanied by a funnel-- shaped cloud that extends down from a huge cumulonimbus cloud. The air pressure at the bottom of the funnel of swirling air is extremely low and causes a giant "vacuum cleaner" effect.

Meteorologists believe tornadoes are caused by a great instability in the atmosphere that is often associated with severe thunderstorms or advancing cold fronts. When these conditions occur, tornado alerts are issued on television and radio. However, tornadoes can occur ahead of warm fronts or even behind cold fronts. It's believed strong updrafts, such as those generated by a severe thunderstorm, and the conservation of rotational momentum, are clues to how the tornado funnels are formed.

The average tornado is about 4/10 of a kilometer in diameter, travels about six kilometers and lasts only a few minutes. During that short amount of time, however, a tornado can do a lot of damage. The wind speeds of tornadoes have been clocked -up to 480 km/hr (more than 300 mph). As a result, roofs and walls of buildings may be blown out. Houses, railroad cars, automobiles and even people can be picked up and thrown hundreds of meters.

You and your students can make a safe miniature model of a tornado using just a few simple supplies.

Materials

Square cardboard box approximately one foot long on each side, knife or scissors, two clear overhead projector sheets, tape, electric heating plate, 4-5" wide aluminum pie pan, water, flashlight, three empty paper towel tubes (or wrapping paper tubes), flat black spray paint.

Procedures

1 Spray the inside of the box with flat black paint and let it dry.

2 Cut two rectangular holes on opposite sides of the cardboard box. These holes should be slightly smaller than the size of the overhead projector sheets. Cover the holes with the projector sheets by taping them to the inside of the box. These are "windows" through which you'll be able to see your tornado.

3 Cut a round hole in the top of the box the size of the diameter of a paper towel tube. Tape the three tubes together to make one long tube and insert it into the hole to a depth of approximately 1 cm, as shown at right. Secure it with tape and be sure it's airtight. This long tube will serve as a chimney for steam that you will create inside the box during the experiment.

4 Cut two slits about 1 cm wide on the two sides of the box that do not have windows. Start the slits I inch from the top of the box and end them about I inch from the bottom, as shown below. These slits are air vents, whose function will be described shortly.

5 Set the electric heating plate to medium-high, place the aluminum pan of water on the heated coils and lower the box over the heating plate.

6 Look through one of the windows while shining a flashlight through the other window. As the water heats up and condenses to form "clouds," observe the miniature funnel that forms.

Explanation

As the water boils, steam is produced and rises up the chimney. The four slits allow cooler air to replace the air that's going up the chimney. Their positions allow the air to rotate due to convection currents. As cooler air rushes into the steam vortex, it forms a funnel-shaped cloud.

Extension

Would a cone-shaped roof with a paper towel chimney create a better funnel? Try it and compare the results to the previous experiment with the flat roof

Books and Websites About Tornadoes

* Tornadoes, Seymour Simon (Morrow, 1999, ISBN 0-688-14646-5)

* Tornado Alley: Monster Storms of the Great Plains, Howard B. Bluestein (Oxford University Press, 1999, ISBN 0-195-105524)

* Twister on Tuesday, Mary Pope Osborne (Random House, 2001, ISBN 0-679-89069-6)

* Under the Whirlwind: Everything You Need to Know About Tornadoes but Didn't Know Who to Ask, Jerrine and Arjen Verkaik (Whirlwind Books, 2001, ISBN 0-968-15374-7)

* Tornado Project Online

www.tornadoproject.com/

* Tornadoes

www.noaa.gov/tornadoes.html

* Severe Storms

www.usatoday.com/weather/tor nado/wtwist0.htm

* Wild Weather

www.usca.sc.edu/AEDC442/44298 4001/tkng.html

* American Red Cross - Tornadoes

www.redcross.org/services/disas ter/keepsafe/readytornado.html

John Cowens teaches science at Fleming Middle School, Grants Pass, OR, and is a Teaching Editor of Teaching K-8. E-mail: snewoc@yahoo.com