Cloud names and classifications

Cloud names and classifications

Clouds are continually changing and appear in an infinite variety of forms. This is a guide to the 10 main named groups of clouds.

Clouds are continually changing and appear in an infinite variety of forms. The classification of clouds is based on a book written by Luke Howard, a London pharmacist and amateur meteorologist, in 1803. His book, The Modifications of Clouds, named the various cloud structures he had studied. The terms he used were readily accepted by the meteorological community and are still used across the world today.

The World Meteorological Organization (WMO) has extended Luke Howard's classifications to make 10 main groups of clouds, called genera. These are divided into three levels - cloud low (CL), cloud medium (CM) and cloud high (CH) - according to the part of the atmosphere in which they are usually found.

The many possibly variations in the shape of clouds and differences in their internal structure have led to the subdivision of most of the cloud genera into species. For a more detailed guide on cloud spotting including species and cloud codes, view our  Cloud types for observers(PDF, 4 MB)  guide.

The names for clouds are usually are combinations of the following prefixes or suffixes:

Stratus/strato = flat/layered and smooth

Cumulus/cumulo = heaped up/puffy, like cauliflower

Cirrus/cirro = High up/wispy

Alto = Medium level

Nimbus/Nimbo = Rain-bearing cloud

Cloud families and other cloud pictures/appearances

In meteorology we divide clouds in 4 clouds families, which are in different heights of the troposphere: High level clouds (altitudes of 5-13 km), medium level clouds (2-7 km), low level clouds (0-2 km) and clouds with large vertical extending (0-13 km).

These clouds families are divided in 10 cloud genus:

Cloud names and classifications
Cloud names and classifications

Cloud level (ft)	Cloud type
High clouds (CH) Base usually 20,000 ft or above, over British Isles	Cirrus Cirrocumulus Cirrostratus
Medium clouds (CM) Base usually between 6,500 and 20,000 ft over British Isles.	Altocumulus Altostratus Nimbostratus
Low clouds (CL) Base usually below 6,500 ft over British Isles.	Stratocumulus Stratus Cumulus Cumulonimbus

Names for clouds :Click on pic of each cloud for more details and pictures:

High level clouds at heights of 5-13 km
name	shortcut	example	meaning
Cirrus	Ci		Fibrous, threadlike, white feather clouds of ice crystals, whose form resembles hair curls.
Cirrostratus	Cs		Milky, translucent cloud veil of ice crystals, which sometimes causes halo appearances around moon and sun.
Cirrocumulus	Cc		Fleecy cloud; Cloud banks of small, white flakes.
Medium level clouds at heights of 2-7 km
name	shortcut	example	meaning
Altocumulus	Ac		Grey cloud bundles, sheds or rollers, compound like rough fleecy cloud, which are often arranged in banks.
Altostratus	As		Dense, gray layer cloud, often evenly and opaquely, which lets the sun shine through only a little.
Low level clouds at heights of 0-2 km
name	shortcut	example	meaning
Stratocumulus	Sc		Cloud plaices, rollers or banks compound dark gray layer cloud.
Stratus	St		Evenly grey, low layer cloud, which causes fog or fine precipitation and is sometimes frazzled.
Clouds with large vertical extending at heights of 0-13 km
name	shortcut	example	meaning
Cumulus	Cu		Heap cloud with flat basis in the middle or lower level, whose vertical development reminds of the form of towers, cauliflower or cotton.
Cumulonimbus	Cb		In the middle or lower level developing thundercloud, which mostly up-rises into the upper level.
Nimbostratus	Ns		Rain cloud. Grey, dark layer cloud, indistinct outlines.
Other cloud pictures and appearances
name		example	meaning
other cloud photos			These photos are not assigned to individual cloud families, because they e.g. show a chaotic sky with many different cloud types or undefinite photos.
other appearances			Appearances, which fit into no other classification