The Crooked, Crazy Weather Project

Student Notes:
Have you ever seen tall, dark puffy clouds forming on a hot humid afternoon?  These are called cumulonimbus clouds, sometimes nicknamed "thunderheads."  They can actually form any time of day when the temperature falls rapidly higher up in the sky.

What is Lightning?

To put it simply, lightning is electricity.  It forms in the strong up-and-down air currents inside tall dark cumulonimbus clouds as water droplets, hail, and ice crystals collide with one another. These collisions build up charges of electricity in a cloud.

 In-Cloud Lightning: The most common type, it travels between positive and negative charge centers within the thunderstorm.

Cloud-to-Ground Lightning: This is lightning that reaches from a thunderstorm cloud to the ground.

Sheet Lightning: This is lightning within a cloud that lights up the cloud like a sheet of light.

Lightning bolts are extremely hot.  When the bolt suddenly heats the air around it to such an extreme, the air instantly expands, sending out a vibration or shock wave we hear as an explosion of sound. This is thunder.

Terrifying Twisters
Some severe thunderstorms may produce tornadoes.  These are violently rotating columns of air in contact with the Earth’s surface.

Ice from the Sky
Hail forms in strong thunderstorms.  These storms contain very strong updrafts, which are winds blowing up through the thunderstorms clouds. Those strong updrafts suspend rain in mid-air with temperatures around the raindrop of below 32 degrees. Those cold temperatures allow the rain to freeze into small hailstones. When hail becomes too heavy for the updrafts to keep it aloft, it falls to the ground.

Resources:
Weather Dude
Thunder sounds
Dan's Wild Weather


Videos:
National Geographic Tornadoes
http://www.weathernetwork.com/lightning


Experiment:   Thunder Boomer
Blow up a small paper bag. Pop it. What happened?  You made the air inside expand quickly, the same way air expands when heated by lightning. You made thunder!