By: Steve Roark
Volunteer, Cumberland Gap National Historical Park

Thunderstorms are common during the hot afternoons of summer, and some folks (like me) are invigorated by all the wind, flashes of light, and noise... a sort of natural fireworks show.

The formation of thunderstorms goes something like this: During the summer the atmosphere is warm and moist from the sun and resulting evaporation that occurs from lakes and soils, plus trees and plants pumping millions of gallons of water into the air as part of the photosynthesis thing. It's not unusual for one large tree to release 95 gallons of water vapor into the atmosphere each day. This warm, moist air rises, and as it does so it cools and condenses, forming clouds, at first only the puffy white cumulus kind. But if there's plenty of heat, or a cold front comes through and pushes the moist air even higher, it can form cumulonimbus clouds. These are thunderstorm makers, and can be identified by a flat, dark bottom, a very tall midsection, and a bright top that often takes on an anvil shape. These clouds can be 7 miles tall and hold a lot of water. When the moisture condenses enough to form rain, it usually occurs in large quantities.

The adrenaline buzz occurs with the lightning and thunder. Lightning is a giant version of static cling that occurs on clothes fresh out of the dryer. In the cumulonimbus cloud, ice crystals and water droplets are in constant motion, bumping into each other violently. This friction builds up static electricity that often separates into two charges: a positive one that goes to the top of the cloud, and a negative charge that goes to the bottom. Eventually the cloud has to release this built-up electrical energy and the discharge is what we call lightning. It can move within one cloud, between separate clouds, or from the cloud to the ground.

Thunder is caused by the lightning bolt superheating the air around it and forcing the air particles to move so fast that it creates a sort of sonic boom. Because light moves so much faster than sound, it is possible to calculate how far away a lightning strike is. Every five-second interval between the flash of lightning and the sound of thunder represents a one-mile distance from the observer.

A bit of mountain slang used by one of my uncles was when a long roll of thunder was heard, he would say “there’s the tater wagon”. Also, some birds referred to as “storm crows”, that when their call is heard it meant a storm was coming. I’ve locally heard mourning doves and yellow-billed cuckoos referred to as storm or rain crows.