Adapted from UCAR/NCAR Web Weather for Kids
Even small thunderstorms are dangerous. Every thunderstorm produces lightning, which kills more people than tornadoes each year. Thunderstorms also cause heavy rain, flash flooding, hail, strong winds and tornadoes. When warm and cold air masses meet, a thunderstorm can grow. In this activity, you will learn about convection and how air moves.
One class period
- One clear plastic container, shoebox size
- Red food coloring
- Ice cubes made with water dyed with blue food coloring
- Colored pencils
- Index cards
- Fill container 2/3 full with room temperature water.
- Let the water sit for 30 seconds until completely still.
- Place a blue ice cube at one end of the plastic container.
- Add two drops of red food coloring to the water at the opposite end of the plastic container. Be careful not to disturb the water.
- Observe where the red and blue food coloring goes.
- Using the red and blue pencils draw what you see happening.
Think About It
Where did the red go? How about the blue? What type of air mass does the red represent? How about the blue? How does this relate to a thunderstorm?
It's all about convection! The cold water sinks while the warmer red water rises, or stays higher than the blue. Convection is the action of warm air rising and cold air sinking. You probably guessed that the blue water represents a cold air mass and the red water represents the warm, unstable air mass. A thunderstorm is caused by unstable air and convection plays an important part. A body of warm air is forced to rise by an approaching cold front. Other things can cause warm air to rise, like a mountain slope.
A strong updraft of warm moist air is formed and lifted by the approaching cold front. Speeds in an updraft can be as fast as 90 miles per hour! The air cools as it rises, condenses, and forms cumulus clouds. When condensation occurs, heat is released and helps the thunderstorm grow.
At some point, condensation high in the cloud (now in the form of water droplets and ice) falls to the ground as rain. A cold downdraft forms as the rain falls.