The Weather

"Eventually it may become saturated and the water vapour then condenses into tiny water droplets, similar in size to those found in fog, and forms cloud. If the temperature falls below about minus 20 °C, many of the cloud droplets will have frozen so that the cloud is mainly composed of ice crystals. The ten main types of cloud can be separated into three broad categories according to the height of their base above the ground: high clouds, medium clouds and low clouds. High clouds High clouds are usually composed solely of ice crystals and have a base between 18,000 and 45,000 feet (5,500 and 14,000 metres). Cirrus - white filaments Cirrocumulus - small rippled elements Cirrostratus - transparent sheet, often with a halo Medium clouds Medium clouds are usually composed of water droplets or a mixture of water droplets and ice crystals, and have a base between 6,500 and 18,000 feet (2,000 and 5,500 metres). Altocumulus - layered, rippled elements, generally white with some shading Altostratus - thin layer, grey, allows sun to appear as if through ground glass Nimbostratus - thick layer, low base, dark. Rain or snow falling from it may sometimes be heavy Low clouds Low clouds are usually composed of water droplets - though cumulonimbus clouds include ice crystals - and have a base below 6,500 feet (2,000 metres). Stratocumulus - layered, series of rounded rolls, generally white with some shading Stratus - layered, uniform base, grey Cumulus - individual cells, vertical rolls or towers, flat base Cumulonimbus - large cauliflower-shaped towers, often 'anvil tops', sometimes giving thunderstorms or showers of rain or snow"