How Do Thunderstorms Form?

Thunderstorms go through three stages in forming. They are born in the cumulus stage, grow in strength in the mature stage, and gradually die in the dissipation stage.

The basis for a thunderstorm’s development is the rising of warm, humid air. As the air rises, the water condenses. As the energy increases inside the storm, the water and ice break up and become electrically charged. Because most of the upper part of the cumulonimbus cloud is positively charged, and the rest of the cloud is negatively charged, a discharge will occur between the cloud and the earth’s surface and lightning is the result. When the lightening heats the air, causing it to expand quickly, the rumbling of thunder is heard.  

Atmospheric stability plays a role in the development of a thunderstorm. That is the term for describing the rising and falling of air. If the air is warmer than the surrounding air, it will rise, and that makes the atmosphere unstable. In contrast, when the air is cooler than the surrounding air, it will sink and the atmosphere is said to be stable. A thunderstorm can not develop in stable conditions. So to further answer the question, “How do thunderstorms form?” it starts with the unstable atmosphere where warm, humid air rises. 

Life of a Thunderstorm

In the cumulus stage, certain things have to take place for the formation of a thunderstorm. As the ground heats up, thermals (rising hot air) are produced.  These cause the clouds to rise into the air. Another cause of rising clouds can be from another storm in the vicinity, which has winds from various directions that can push the clouds up.

As the air cools with the higher elevation, water condenses and forms droplets.  This causes the cumulus clouds which in turn, cause an updraft because heat is released during condensation. This updraft  causes a low pressure area beneath the thunderstorm, which continues the cycle of rising air and condensation.  

When the thunderstorm has reached the “cap,” it is at the point where air cannot rise any higher. The clouds become cumulonimbus clouds, as the water droplets start to merge with one another, the clouds become heavier, and water begins to freeze. The ice will return to rain as it falls and melts. There is a continuous updraft and the falling rain produces a down draft. This turbulence creates wind, positive and negative charges make lightning, and tornadoes may form.   

The dissipation stage starts after the thunder and lightning of the mature stage.  It is controlled by the downdraft or downburst, where the wind hits the ground and spreads out. The cool air carried out of the thunderstorm by the downdraft effectively cuts off the inflow and the storm weakens.    

Watches and Warnings

A severe thunderstorm watch, issued by the National Weather Service, means that conditions are favorable for the development of severe thunderstorms. If it seems that the thunderstorm can produce a tornado, then a tornado watch is issued, which implies a severe thunderstorm watch.  

A severe thunderstorm warning means that storm spotters or Doppler radar indicates that a storm is producing hail at least one inch in diameter, winds at 58 miles per hour or higher, and tornadoes, or any combination of those three things are occurring.     

Preparing for a Severe Thunderstorm

It is important that your yard be clear of debris, like dead trees or branches that could cause damage if a severe thunderstorm occurs. If there is lightning and you can hear thunder, go indoors.  

To stay safe from lightning strikes while inside your home, avoid contact with corded phones and electrical equipment or cords. Unplug electrical appliances and turn off air conditioners. Do not have contact with plumbing, which includes taking a bath or shower, washing dishes, washing your hands, or doing laundry. Stay away from windows, doors, and porches. Do not lie on a concrete floor or even lean against a concrete wall.  

If you are outside, a car will provide a measure of protection as long as it is not a convertible and you do not touch metal. If you are in an open area, go to a low area, and if you feel your hair standing on end, that means lightning is about to strike. Lean over and squat on the ground with the balls of your feet. Put your head between your knees and put your hands over your ears. This will minimize contact with the ground and you will make yourself a small target. Whatever you do, do not lie flat on the ground.