Tornado Box

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Earth Science: Cyclone Formation
Grade Range: Elementary School, Middle School
Format: Hands-on

The Tornado Box can be set up before the start of the event, and is fairly self sufficient. Watch it during the event to make sure there is enough water, and add an extra chunk of dry ice every 10-15 minutes.

Contents

Materials

  • The Tornado Box
  • Small Metal Bowl
  • Dry Ice
  • Hot Plate
  • Water

Safety Precautions

Please read the Cryogen Safety section of the Demonstration Safety page before performing this demonstration. Keep towels on hand in case of spilled water.

Demonstration

  1. Plug in the hot plate and turn it to medium/low heat. place the bowl with water in it on top of the plate and allow it to heat up. You want the water to be hot, but not boiling or simmering.
  2. Set the tornado box around the hot plate, with the windows facing outward for students to look in. Put a large piece of dry ice into the bowl of water, and adjust the slots on the side of the box. You want to get the slots open enough to allow a cyclone to form in the rising cloud from the bowl. The breeze in the room and the temperature of the water will affect how big or small the slots need to be.
  3. Once set up, students can come check it out and adjust the slots to see if they can change the size of the cyclone, or if a cyclone isn't there they can try to make it. Watch the demonstration and add dry ice and water as needed throughout the event.


Why This Works

Meteorology is the study of the weather and weather systems, like hurricanes, tornadoes and cyclones. Tornadoes and cyclones are powerful spinning winds that can topple houses and send trees flying. In order for them to form, however, there are a few things that need to happen. First, there needs to be warm, moist air. Warm, moist air is less dense than dry air, so it will want to rise above the air around it. This is part of the reason why you will see a shelf cloud in front of a storm, or a wall cloud form inside of a storm; that area is an area with a strong updraft, due to the warm, humid air rising above the air around it. Second, there needs to be a cross breeze. A cross breeze means that there is air blowing in more than one direction, and these breezes are colliding with each other. You may haven already seen what a small cross breeze can do; If you have ever seen a little "leaf tornado" or a small whirlwind, those are created by two breezes colliding. Lastly, these two things need to happen close to the same spot. If these conditions are all met, you will see a cyclone form!

For our tornado box, you can adjust the size of the cyclone by changing how big the slots are. if the slots are wide open, then the cross breeze will be weak, so the cyclone might not form, or if it does then it will be really wide and slow spinning. If the slots are mostly closed, then the cross breeze will be strong, and you should see a thin and fast spinning cyclone!

Additional Information

  • This demonstration accurately shows the formation of a tornado, but we see it form bottom-up rather the usual top-down that we would see in nature. This is because in nature, the cloud above has a strong downdraft of cool, moist air close to the strong updraft of warm, moist air. These two moving air systems create a cross breeze, and therefore a cyclone, which grows bigger as the cool, moist air continues to move down towards the ground. Because of that, we watch the tornado form top-down!
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