Tornado!

INTRODUCTION

Tornadoes are extremely violent wind storms capable of wind speeds of more than 300 miles per hour. Although tornadoes are relatively small in area and short lived, they contain very large amounts of energy and can have devastating effects. Severe thunderstorms provide the conditions necessary for tornado formation, including quickly changing wind speeds and directions and warm, moist, fast-rising air colliding with incoming cool, dry air. Let’s take a closer look at how these conditions allow tornadoes to form . . .

MATERIALS

• Hot plate
• Round metal baking dish (8 inch diameter)
• Water
• Cardboard tube, 2-3 feet long, 4-inch diameter
• Wooden kitchen matches
• Black Construction Paper, 2 - 7 ½ inch squares and 4- 9-inch X 1-inch rectangles
• Tape
• Tornado box
  • Base: 1 Metal 9-inch square with upward-opening grooves along all sides, with 6-inch diameter circle cut from the center of the square.
  • Sides: 4 Plexiglas 8-inch squares
  • Top: 1 Metal 9-inch square with downward-opening grooves along all sides, with 4-inch diameter circle cut from the center of the square.
  • Assembly Instructions: Place the base on a flat surface with the grooves facing up. Slide one Plexiglas piece into the groove on each side of the base. (There will be openings at the corners of the box) Position the top so that each of the Plexiglas sides fits into a downward-facing groove.

WHAT TO DO

1. Tape a piece of construction paper to the outside surface of two adjacent sides of the tornado box. This will help make the tornado more visible once it forms.
2. Fill the baking dish most of the way with water and place the dish on the hot plate. Position the tornado box on top of the baking dish so that the 6-inch hole in the base of the box is centered over the baking dish. Place the cardboard tube on top of the box, centered over the 4-inch circular opening. The tube will serve as a chimney.
3. Turn the hot plate on and set it at medium high. BE CAREFUL! The hot plate, baking dish, and the base of the tornado box will become VERY HOT. Because these surfaces will be very hot through out the activity, only adults should be touching the set up. Students can watch closely, but they SHOULD NOT TOUCH ANY PART OF THE TORNADO SET UP.
4. Allow time for the water to warm and begin to heat and humidify the air inside the tornado box. Watch carefully. The air inside the box will begin to move and its currents will be faintly visible against the black background on the back sides of the box.
5. When the air in the box is swirling rapidly light a match. Away from the corner openings of the tornado box blow out the match, but while it is still smoking hold it near one of the openings. The smoke will help make the moving air inside the box more visible.
6. Can you see the tornado?
7. Remove the chimney. Use another match to help see the movement inside the box. Can you still see the tornado? Think about why or why not.
8. Replace the chimney and wait a few moments for the air currents to reestablish themselves. After the tornado has formed again you may proceed to the next step.
9. Slide one of the Plexiglas sides over to create a very large opening in the front of the tornado box. Use another match to help see the movement inside the box. Can you still see the tornado? Think about why or why not.
10. Replace the side and wait a few moments for the air currents to reestablish themselves. After the tornado has formed again you may proceed to the next step.
11. Tape a paper rectangle loosely over each of the corner openings of the box. Wait a few moments. Use a match to help see the movement inside the box. Can you still see the tornado? Think about why or why not.
12. Remove the paper corner coverings and wait a few moments for the air currents to reestablish themselves. After the tornado has formed again you may proceed to the next step.
13. Can you think of any other changes you would like to test? Before testing them, make a guess about how you expect that change to affect the tornado inside the box. Then, test your hypothesis.
14. When all changes have been tested, turn off the hot plate and allow the tornado set up to cool before dissembling it.

QUESTIONS

1. What are two of the things needed for a tornado to form? How were those two things simulated in our tornado model?
2. Why did the tornado in the box change when the chimney was removed? When the side was opened wide? When the side openings were covered?

SUMMARY

Tornadoes are formed when warm humid air quickly rises and cool dry air rushes in to replace it. Currents in the air begin to swirl around the storm’s low-pressure center at high speeds. Dust and debris are lifted by the storm’s fierce winds and much destruction results. Tornadoes can uproot trees, pull the roofs off houses, and demolish almost anything in their paths.

The tornado box used here helps see how tornadoes are formed. As the water in the baking pan is warmed it warms the air in the tornado box. Evaporation of the water in the pan makes the warm air in the box very humid, as well. Warm air rises due to its’ low pressure, and the chimney attached to the opening in the top of the box helps the warm humid air rise quickly. The openings at the box’s corners allow the cooler, drier air from the rest of the room to rush into the box to replace the warm air. The cool air and the warm air interact inside the box to form swirling currents, and before long a funnel shaped cloud of condensing water is visible. The cloud is made more visible by allowing lightweight particles of smoke to be drawn into the box.

Changing the conditions by altering any part of the tornado box assembly will change the behavior of the air inside the box. For example, removing the chimney prevents the warm air from rising as quickly, so less cold air is drawn in, and the air currents needed for the tornado do not form.

SOURCES

Jym Ganahl - tornado box design
How the Weather Works

© S. Olesik, WOW Project, Ohio State University, 2002.