The Atmosphere
Movement in the Atmosphere
Atmospheric Stability
Localised Winds
Visibility and Fog
Aircraft Icing
Weather Reports and Forecasts
Practice Exam

Stages of a Thunderstorm

There are three stages to the life cycle of a thunderstorm and each is defined primarily by the movement of air within the cloud.

Cumulus or Developing Stage

At this stage, all the air movement within the cloud is upwards. The tops and sides of the cumulus are growing and large water droplets are suspended in the updraughts. Some rain or virga may be present.

The cloud is bright white and the edges are sharply defined. The surrounding air is being sucked into the cloud from below and the sides.

Mature Stage

Water droplets have grown larger and rain starts falling from the cloud base. Downdraughts form and the unstable nature of the cloud can cause the downdraughts to be very strong. There are now both updraughts and downdraughts within the cloud, creating strong wind shear and severe turbulence as the two interact.

Lightning and hail are common in the mature stage.

The top of the cloud often reaches the top of the troposphere, where the cloud top then spreads out into the classic anvil shape.

Dissipating Stage

The dissipating stage starts when the updraughts have stopped. The whole cloud is now colder than the surrounding air, so it slowly begins to subside and warm. This can create some strong downdraughts at first, but as the overall temperature of the cell approaches the environment temperature the downdraughts weaken. The cloud starts to evaporate and the edges appear ragged.

A great timelapse video of a thunderstorm forming can be seen on YouTube here:

The terms thunderstorm and cumulonimbus are often used interchangeably. Strictly speaking, a cumulonimbus is the cloud type where as a thunderstorm refers to the weather phenomenon associated with a cumulonimbus cloud – primarily lightning and thunder