3 Stages of a Thunderstorm

The Three Stages of a Thunderstorm

Thunderstorms require three ingredients for them to exist. There must be moisture in the air, an unstable atmosphere, and a lifting force. Once all these are present, then the excitement begins…

The Cumulus (developing) Stage

The Cumulus stage is the first stage. Pilots will experience updrafts when in the vicinity of these clouds. Depending on the severity of the updrafts these clouds can reach an altitude of more than 60,000 feet (rare, but possible). Clouds with extensive vertical development are referred to as towering cumulus. Because of continuous updrafts, there is no precipitation. Once these updrafts give, we move to the next stage.

The Mature Stage

An example of a Mature Thunderstorm and its dangers.

In the Mature Stage, there are both updrafts and downdrafts present. The beginning of rainfall signals the beginning of the mature stage. This is the most dangerous stage of a thunderstorm because it’s where most of the excitement happens. Pilots can experience lightning, severe turbulence, wind gusts, and even hail. Hail has been observed to travel more than 20 nautical miles from a storm.

There are many signs that pilots can observe during the day to forecast the dangers of a storm, but common practice is to circumnavigate the storm by at least 20 nm on the upwind side. A very dangerous phenomenal called microbursts can occur at this stage. Microbursts have downed airliners in the past like Delta Flight 191, a Lockheed L-1011 which experienced a microburst during an instrument approach that they couldn’t fly away from. Small general aviation airplanes should not be getting anywhere near these storms.

An easy way to determine the movement of a storm is by observing the direction of the cloud anvil as it always appears on the downwind side.

The Dissipating Stage

This is the end of a thunderstorm, at this point, due to a lack of warm rising air, moisture is gone and the storm mostly consists of downdrafts. These downdrafts are signs that the storm is dying out. Light rain and light winds can still be present. This light rain rarely is a danger to light aircraft but can still affect visibility.

Identifying which stage a thunderstorm is in can be tricky; remember always check the weather radar of your flight path area, monitor the Automatic Terminal Information Service (ATIS) of local airports, and when in doubt, keep a distance of 20 nm on the upwind side of any potential storms. Following these simple steps could save you from a lot of trouble.