Lightning

The past few days we have seen several rounds of thunderstorms move through Bowling Green bringing heavy down pours, high winds and frequent lightning. I had a chance to get out and do one of my favorite things, which is document storms and take pictures, of course. Bowling Green and the surrounding areas had tons of lightning and a lot of it was hitting the ground. I figured this was a good opportunity to take a look at some lightning information.

Lightning is simply a large discharge of electricity which mostly occurs within mature thunderstorms. It can also occur within convective snow or sleet bands and in volcanic eruptions. Lightning strokes are extremely hot and can heat the air surrounding it to around 54,000 degrees F, that’s 5 times hotter than the surface of the sun.

This rapid heating of the air is so intense and quick that it creates a shock wave which is audible and travels out from all directions, creating a clap of thunder. Let’s take a look at how it is formed; (and this is a great animation for my last post on air mass thunderstorms).

Essentially, a thunderstorm updraft contains areas with different electrical charges. Smaller, lighter particles are carried to the top of the thunderstorm by the strength of the updraft and have a positive charge. Heavier, particles such as hails stones or graupel, usually position in the lower part of the thunderstorm and contain a negative charge. A separation of charges is maintained throughout the storm’s mature stage and the bottom area of the storm remains negatively charged as it moves along across the landscape.

Because opposite charges attract one another, a positive charge develops on the ground below the storm. Objects such as trees or telephone poles typically contain the most dense area of positive charge as they protrude up into the air. After awhile, insulating properties of the air begin to break down, and if the charge gradient is strong enough, a lightning strike occurs, allowing an electrical current to flow between the cloud and ground.

Not all lightning occurs between the cloud and ground, however. Often times the discharge of electricity can occur within the cloud itself or between different clouds. In-cloud lighting is very common and usually generates that slow, rumbling kind of thunder we often hear whereas cloud-to-ground lighting generates a more distinct clap of thunder.

Since sound waves travel much slower than light, a good rule of thumb to remember is that after you see a flash of lightning, wait until you hear thunder, every 5 seconds represents a distance of 1 mile. After about 10 miles however, due to different properties of sound, you usually can no longer hear thunder.

On average, the United States witnesses around 25 million lightning strikes each year; a good deal of them coming from the state of Florida. Lightning is very dangerous and should be taken seriously. “When the thunder roars, go indoors” is a safety slogan from the National Weather Service.  The National Weather Service has a webpage dedicated to lightning information along with some great safety tips.