Last week we were sent in this beautifully structured cumulonimbus cloud by Kevin B at its 'mature stage', but what does that mean?

A cumulonimbus cloud, also known as a storm cloud, is a towering, multi-level cloud capable of producing rainfall and lightning. Cumulonimbus clouds can be broken down into three different stages in their life cycle, each with different features:

Cumulonimbus first develop from large cumulus congestus, when they start to lose their cauliflower-like appearance and are growing into the tropopause, as a result of rising columns of warm air.

In this stage, the tropopause, or the top of the troposphere, is reached, and air is forced outward, horizontally, at the temperature inversion. Consequently, a flattened anvil is formed, as pictured in Kevin's shot.

An overshooting top is also captured, where a dome-like protrusion shoots out the top of the anvil, which indicates strong updrafts as it is able to briefly push into the lower stratosphere.

When the convection and subsequent updrafts needed to sustain the cloud dies away, the cloud itself begins to dissipate. The anvil is usually one of the last features to die away.