Thunderstorms and Twisters: What are Tornadoes and How Do They Form?

 Tornadoes are some of the most violent and dangerous storms.  While they are usually short-lived (most last less than 10 minutes according to the National Weather Service), some can last more than one hour.  Even in a short time on the ground tornadoes can take lives, cause terrible injury, and do millions of dollars worth of damage.  So why do tornadoes form in the first place?

Before we discuss how tornadoes form, it’s important that we understand thunderstorms.  Thunderstorms occur when warm, moist air rises from the surface of the earth, cooling and condensing into clouds as they reach higher altitudes where the temperatures are colder.  These clouds then produce rain, causing rapid downward-moving cool air known as a downdraft.  Usually this downdraft and its cool air quench the updraft, and the storm ends.  However, occasionally a thunderstorm will develop into a much stronger, more violent storm called a supercell. 

Supercells are different from normal thunderstorms because they rotate; they form when the air near the Earth’s surface and the air at higher elevations are moving in different directions, causing internal rotation of the clouds.  This phenomenon is called wind shear, and frequently happens when cool, dry air moving south from Canada reaches areas where warm, moist air is moving north from the Gulf of Mexico. 

Because of this wind shear, the air begins to rotate horizontally.  This combined with the strong updrafts from the rising warm air near the Earth’s surface cause the rotation to become vertical; this vertical rotation is called a mesocyclone. 

As the storm intensifies, the cooling rain and resulting downdraft begin to drag the mesocyclone downward toward the ground.  Continuing updrafts intensify also, creating an area of low pressure near the ground, dragging the rotating mesocyclone down further.  Eventually this rotation touches the ground, officially becoming a tornado.  

BUILD A WATER TORNADO!

Here’s what you’ll need:

1.       Two empty, clear 2-liter soda bottles

2.       Duct tape

3.       Super glue (you could use calking from a hardware store also)

4.       Enough water to fill one soda bottle about ¾ full. 

Here’s what you need to do:

1.       Remove the caps from your bottles

2.       Fill one of your empty bottles with water until it is ¾ full

3.       Turn the other empty bottle upside down, and use the super glue or caulk to glue the openings of the two bottles together.

4.       Wrap the duct tape around the openings of the bottles and up the sides of each bottle, so that the duct tape is wrapped securely around not only the necks of the bottles but also at least ¼ of the main body of each bottle.

5.       Allow the glue to dry for at least 20 minutes

6.       Once the glue is dry, rapidly turn the bottles over so that the water is at the top.  Do not shake or rotate the bottles.

7.       When all the water has gone from the top bottle to the bottom, write down your observations

8.       Next, turn the bottles over again, but this time swirl the water in a clockwise motion as you turn the bottle over.

9.       When all the water has gone from the top bottle to the bottom, write down your observations

What happened the first time you turned the bottles over?  What about the second time? 

What effect did rotating the bottles have?  How is this like how a tornado forms? 

Be sure to write down all your answers and observations!