'Round and 'Round
Kathleen Damonte
Summer is coming. Hot weather means sandals, ice cream, pool parties, and occasionally really large thunderstorms. Sometimes really powerful thunderstorms produce tornadoes. Tornadoes are the most violent kind of storm and can be extremely dangerous. Everyone should be knowledgeable about tornadoes because they can occur anywhere.
 A tornado is a rotating, funnel-shaped column of air, which extends from a thunderstorm to the ground. (Learn more about thunderstorms in this month’s Science 101 column.)The winds of a tornado can reach up to 480 km per hour. This is about five times faster than a car driving on a highway. Tornadoes can be almost invisible until they pick up dust and debris.
In the United States, the strength of a tornado is rated on a scale created by a meteorologist named Theodore Fujita. The Fujita Pearson Scale is based on the damage a storm causes to manmade structures and ranks storms from an F–0 to an F–5. An F–0 storm causes damage to roofs and street signs. An F–5 storm moves houses off their foundation and throws cars hundreds of feet. A very small percentage (about two percent) of tornadoes get ranked as F–4 or F–5 each year.
Where and When Do Tornadoes Occur?
The United States has more tornadoes occur each year than any other country. An average of 800 tornadoes occur in the United States each year. Every state is at some risk for tornadoes, but some states more so than others. The states in “Tornado Alley”—Arkansas, Iowa, Kansas, Louisiana, Minnesota, Nebraska, North Dakota, Ohio, Oklahoma, South Dakota, and Texas—have the highest risk. These states are located in the central part of the United States and have geography that suits the formation of tornadoes.
Tornadoes can form any time during the year; however, the typical tornado season runs from March until August. Meteorologists use weather radar to keep track of developing storms. Early detection of the conditions where tornadoes can form allows meteorologists to issue watches and warnings to areas where a tornado might occur.
Try the activity below to simulate tornado movement with simple materials.
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Tornado in a Jar
Materials:
- A large glass jar with lid (a mayonnaise jar or canning jar works well)
- White vinegar
- Liquid dish soap
- Water
- One teaspoon
- Glitter (optional)*
Time needed: 10 minutes
Safety Warning: Do this activity with a grown-up. Be careful when working with the glass jar so it doesn’t break.
Directions:
1. Fill the jar about three-quarters full with water.
2. Add two teaspoons (10 mL) of white vinegar to the jar and one teaspoon (5 mL) of liquid dish soap.
3. Screw on the lid as tightly as you can and dry the outside of the jar so it won’t be slippery. Shake the jar very lightly—just to mix up the ingredients.
4. Holding the jar around the middle, move the jar around in a circular motion to get the contents moving. Be careful not to drop the jar.
5. The liquid will form what looks like a small tornado. See if you can change the size, shape, or direction of the tornado.
*You can get creative by adding glitter to represent dust and debris picked up by the tornado.
Explanation:
The swirling motion you give the jar as you move it causes the liquid to form a vortex that simulates the movement of a tornado. A vortex is a whirling mass of something, usually water or air, that draws everything near it towards its center.
For Older Students:
Here is a chance to hone (practice and improve) your research skills. Use the Internet to find the answers to the following questions about tornados.
- How many tornados occurred in your state this year? Last year?
- What is the difference between a tornado watch and a tornado warning?
- Can you find a description of the damage to manmade structures at each level of the Fujita Pearson Scale (F-0 to F-5)?
- In what direction do most tornadoes in the Northern Hemisphere move (clockwise or counter-clockwise)?
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Visit the following website for more information about tornadoes:
The Online Tornado FAQ
www.spc.noaa.gov/faq/tornado
Kathleen Damonte teaches seventh-grade science at Julius West Middle School in Rockville, Maryland.
 Click here for PDF file.
Copyright © 2004 NSTA
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May 2004, p. 49-50