4Warn Weather – Let’s talk about the science behind those bright flashes of lightning across the sky.
Storm Clouds
Thunderstorm clouds have a lot of air moving around inside them, including updrafts and downdrafts, which can be strong.
Updrafts transport tiny drops of rain and ice crystals to the top of the thundercloud, which can be between 35,000 and 70,000 feet above the ground!
As water droplets and ice pieces collide, graupel and hail form, which can be carried to the bottom of the cloud by downdrafts or simply fall lower due to weight.
With all of this colliding, electrons are sheared off the rising particles.
Collecting on descending particles yields a thunderstorm cloud with positively charged particles near the top and negatively charged particles at the bottom.
Lightning Strikes
Energy builds, creating an electric field inside the cloud. Eventually, there is so much energy that it needs to be released; that discharge of energy is the bolt of lightning we see.
Lightning occurs within a cloud, between clouds, and between a cloud and the ground.
A channel of negative charges, or what’s called a stepped leader, will zig-zag down toward the ground, typically in approximately 50-meter increments.
A positively charged channel, or upward streamer, will reach up from the ground to the stepped leader.
When the two connect, the energy is discharged, and that electrical transfer is a bolt of lightning.
This all happens very quickly.
The discharge of energy heats the air rapidly, reaching temperatures up to 50,000°F - that’s five times hotter than the surface of the sun.
That air expands with the heat, then cools and contracts right after the flash.
That fast expansion and contraction of the air is what creates the sound wave we hear as thunder.
Fast Facts
- Heat lightning does NOT exist. This is simply when you can see lightning but are too far away from the storm to hear the thunder.
- The average person can typically only hear thunder within ten miles of a storm. Since lightning can strike up to twelve miles away from a storm, whenever you hear thunder, you should go inside. On quiet days, thunder can be heard from over twenty miles away from a storm.
- It takes the sound of thunder about five seconds to travel a mile. Therefore, if you count the seconds between a flash of lightning and the sound of thunder, then divide by five, the result will be the distance to the lightning in miles. For example, five seconds is one mile, fifteen seconds is three miles.
Just remember that if you hear thunder, chances are that you’re within a lightning strike’s distance from a storm, and you should go indoors.