Clouds with important vertical extension

Nimbostratus

Cumulonimbus

Cumulus

Nimbostratus (Ns): It is a cloud of vast horizontal and vertical measurements. It often brings rain or snow. Because of its thickness, its base is very dark. It often comes with Sc and St. It is the typical cloud of the long rainy days because it is stable.

Cumulonimbus (Cb): It is a dense and powerful cloud and it has a considerable vertical extension. It is shaped like a mountain or an enormous tower. Its upper part is like an anvil or feathery. Its base is often doubled with low and jagged clouds. The Cb generates storms. It is an unstable cloud (fig. 16).

Finally a last group of cloud exists but it is difficult to classify them.

Cumulus (Cu): They are separate clouds with distinct contours. They expand vertically in cauliflower shapes. The Part of these clouds illuminated by the sun are very white, whereas the base are generally dark and horizontal. The thickness of a cumulus cloud varies from about 10 metres to several kilometres. It is the case of congestus cumulus which is the state preceding the cumulonimbus.

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