Why does lightning sometimes hit the ground and other times go from cloud to cloud?

Answered by Travis Wyatt, National Weather Service, Pocatello Office

All lightning comes from thunderstorms. When a thunderstorm develops, electrical charges (either positive or negative) within the cloud separate. This creates two different electric fields between the top of the cloud and the base of the cloud. When these electric fields build up enough, there is rapid discharge of electricity that we know as lightning. The electric field within the storm is not the only one that develops. Below the negatively charged storm base, positive charge begins to pool within the surface of the earth (image d). This positive charge will shadow the thunderstorm wherever it goes, and is responsible for cloud-to-ground lightning (image d). However, the electric field within the storm is much stronger than the one between the storm base and the earth’s surface, so most lightning occurs within the storm cloud itself.

lightning1
Lightning can happen: a) inside-a-cloud, b) cloud-to-cloud, c) cloud-to-air, and d) cloud-to-ground.

  1. Inside-a-Cloud or Intra-Cloud: This is the most common type of lightning. It happens completely inside the cloud, jumping between different charged regions in the cloud. Intra-cloud lightning is sometimes called sheet lightning because it lights up the sky with a ‘sheet’ of light.
  2. Cloud-to-Cloud: Lightning that occurs between two or more separate clouds.
  3. Cloud-to-Air: Lightning that occurs when the air around a positively charged cloud top reaches out to the negatively charged air around it.
  4. Cloud-to-Ground: Lightning that occurs between the cloud and the ground.

NOAA Resources: https://www.weather.gov/media/pah/WeatherEducation/lightningsafety.pdf
http://www.srh.noaa.gov/srh/jetstream/lightning/lightning.html


Static Electricity
Lightning is the flash of light produced by the natural discharge of a large amount of static electricity. Static electricity often happens when you rub things together. If you rub a balloon against your hair 20 or 30 times, you’ll find the balloon sticks to your hair. This happens because rubbing the balloon gives it a negative electric charge (a small amount of electricity). The charge makes it stick to your hair like a magnet, because your hair gains an opposite (positive) electric charge. So your hair and the balloon attract one another like the opposite ends of two magnets.

Materials: scissors, produce bag, balloon, cotton towel

  1. Cut a 2-inch strip from the open end of the produce bag. You will have a plastic band or ring.
  2. Blow up a balloon to its full size and tie off the end.
  3. Rub the cotton towel over the surface of the balloon for 30-45 seconds.
  4. Flatten the plastic band on a hard surface and gently rub the towel on the band for 30-45 seconds.
  5. Hold the plastic band about one foot over the balloon and release it. The plastic band is levitating! The plastic bag and the balloon are both negatively charged and repel each other.

lightning2

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