A thunderstorm is a storm with lightning and thunder. It’s produced by a cumulonimbus cloud, usually producing gusty winds, heavy rain and sometimes hail.
Causes a thunderstorm
The basic ingredients used to make a thunderstorm are moisture, unstable air and lift. You need moisture to form clouds and rain. You need unstable air that is relatively warm and can rise rapidly. Finally, you need lift. This can form from fronts, sea breezes or mountains.
A thunderstorm is classified as “severe” when it contains one or more of the following: hail one inch or greater, winds gusting in excess of 58 mph (50 knots), or a tornado.
Stages of a thunderstorm
Thunderstorms have three stages in their life cycle: The developing stage, the mature stage, and the dissipating stage. The developing stage of a thunderstorm is marked by a cumulus cloud that is being pushed upward by a rising column of air (updraft). The cumulus cloud soon looks like a tower (called towering cumulus) as the updraft continues to develop. There is little to no rain during this stage but occasional lightning. The thunderstorm enters the mature stage when the updraft continues to feed the storm, but precipitation begins to fall out of the storm, creating a downdraft (a column of air pushing downward). When the downdraft and rain-cooled air spreads out along the ground it forms a gust front, or a line of gusty winds. The mature stage is the most likely time for hail, heavy rain, frequent lightning, strong winds, and tornadoes. Eventually, a large amount of precipitation is produced and the updraft is overcome by the downdraft beginning the dissipating stage. At the ground, the gust front moves out a long distance from the storm and cuts off the warm moist air that was feeding the thunderstorm. Rainfall decreases in intensity, but lightning remains a danger.
Before a thunderstorm
- Remove dead tree branches near your house which could ignite and cause a fire if struck by lightning.
- Unplug all appliances before the storm hits to prevent power surges.
- Close blinds and shades.
During a thunderstorm
- Keep away from windows.
- Avoid using the phone. Telephone lines can conduct electricity.
- Stay away from faucets, sinks and bathtubs.
- If you are in or near water, go to land immediately and find the best shelter you can— preferably inside a building rather than a car.
- If you’re in a car, keep the windows closed. Pull to the side of the road to wait until the heavy rain subsides. Keep away from trees that could fall on your car.
- If you are outside, find a location that is not likely to flood. Avoid tall structures, such as towers, trees, fences, telephone lines or power lines.
- Squat low to the ground and assume a tucked position. Place your hands on your knees with your head tucked between them. Try to touch as little of your body to the ground as possible. Do not lie flat on the ground, as your fully-extended body will provide a larger surface to conduct electricity.
- If you feel your hair stand on end in a storm, drop into the tuck position immediately. This sensation means electrical charges are already running up your body from the ground toward an electrically charged cloud. If you can minimize your contact with the ground, you will minimize your injury.
After a thunderstorm
Once lightning has struck a person or an object, the person or object does not carry a charge and cannot harm you. So don’t be afraid to touch or assist a person who needs help. A lightning victim usually suffers burns in two places on the body—where the lightning entered and where it exited.