All high clouds are a type of cirrus, a common cloud that can be seen at any time of the year.
Height of base: 18,000 - 40,000 ft
Shape: Layered, tufty or patchy
Latin: cirrus - lock or tuft of hair
Cirrus clouds are short, detached, hair-like clouds found at high altitudes. These delicate clouds are wispy with a silky sheen or look like tufts of hair. In the day time, they are whiter than any other cloud in the sky. While the sun is setting or rising, they may take on the colours of the sunset.
Cirrus clouds form from the ascent of dry air, making the small quantity of water vapour in the air to sublime into ice (sublime means to change from a gas directly into a solid). Cirrus are made up completely of ice crystals which provides their white colour and form in a wide range of shapes and sizes.
Cirrus clouds can also form through contrails, the vapour trails left by planes as they fly through a dry upper troposphere. These streaks can spread out and become cirrus, cirrostratus and cirrocumulus.
They often form in advance of a warm front where the air masses meet at high levels, indicating a change in the weather is on the way.
Technically these clouds produce precipitation, however it never reaches the ground, but instead 're-evaporates' creating virga.
Cirrus clouds have five defined 'species';
Last updated: 3 August 2016