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Cloud Types and Precipitation

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There are ten main cloud types, which are further divided into 27 sub-types according to their height shape, colour and associated weather, Clouds are categorised as low (from the earth's surface to 2.5 km), middle (2.5 to 6 km), or high (above 6 km). They are given Latin names which describe their characteristics, e.g. cirrus (a hair), cumulus (a heap), stratus (a layer) and nimbus (rain-bearing). Clouds generally look white with some clouds appearing to be grey or dark grey according to their depth and shading from higher cloud.

Typical Examples of the 10 Main Cloud Types

High Level Clouds (above 6 km)

Cirrus

Cirrus: high level, white tufts or filaments; made up of ice crystals.
No precipitation.

Cirrocumulus

Cirrocumulus: high level, small rippled elements; ice crystals.
No precipitation.

Cirrostratus

Cirrostratus: high level, transparent sheet or veil, halo phenomena; ice crystals.
No precipitation.

Middle Level Clouds (2.5 to 6 km)

Altocumulus

Altocumulus: middle level layered cloud, rippled elements, generally white with some shading.
Precipitation: May produce light showers.

Altostratus

Altostratus: middle level grey sheet, thinner layer allows sun to appear as through ground glass.
Precipitation: rain or snow.

Nimbostratus

Nimbostratus: thicker, darker and lower based sheet.
Precipitation: heavier intensity rain or snow.

Low Level Clouds (below 2.5 km)

Stratocumulus

Stratocumulus: low level layered cloud, series of rounded rolls, generally white.
Precipitation: drizzle.

Stratus

Stratus: low level layer or mass, grey, uniform base; if ragged, referred to as 'fractostratus'.
Precipitation: drizzle.

Cumulu

Cumulus: low level, individual cells, vertical rolls or towers, flat base.
Precipitation: showers or snow.

Cumulonimbus

Cumulonimbus: low level, very large cauliflower-shaped towers to 16 km high, often 'anvil tops'. Phenomena: thunderstorms, lightning, squalls.
Precipitation: showers or snow.

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