This storm became severe about 45 mins after this photo, giving very heavy hail

This weak cumulonimbus has formed as cool, dry continental air blowing off the land passes over warmer moist air over the ocean.

This cumulonimbus is affected by strong wind shear. The updraft is almost 45 degress to vertical. Such conditions can lead to severe storms, as was to case with this storm.

Cumulonimbus with pileus cloud - pileus indicates that updrafts are very strong. ( Yamba, New South Wales )

Not all large cumulonimbus are thunderstorms, this system brought very heavy rains with flash flooding, a cirrus crown is clearly visible.

A gustfront - cloud that is formed as cooler air pushes away from the thunderstorm downdraft / outflow.

This cumulonimbus displays a large rock hard anvil with some back building. There is also a flanking line feeding into the storm.

A storm with severe features - most notably the downburst & greenish tinge, which can indicate hail. ( Yamba, New South Wales )

Cumulonimbus Calvus - the stage immediately before glaciation and anvil formation.