31 July 2011
Last updated at 00:47
Cloudy weather and the British summer go hand in hand. Here, the Met Office's John Hammond decodes cloud photos sent by viewers of BBC One's The Great British Weather. These mammatus clouds, underneath a cumulonimbus cloud, were spotted by Patsy Hampson in Douglas, Isle of Man. "These unusual looking clouds - named after the Latin word for breast - are caused by down draughts associated with a thunderstorm," says Hammond.
"Towering cumulus clouds typically appear on showery days. In John Short's photo it's possible to see rain falling from the cloud base," says Hammond.
Nanette Stewart captured bands of altocumulus clouds in Wick, north Scotland. "These are formed due to the air travelling up and down by the presence of hills and mountains. Where the air is rising, there is a band of cloud - and where the air is descending, there are clear skies," says Hammond.
The stratocumulus clouds in John Hall's photo are being illuminated from beneath by the setting sun. "Stratocumulus is normally the most common cloud we see across the British Isles, but the sun is giving it a rare radiance," says Hammond.
Alan Tough spotted these rare noctilucent clouds in Elgin, Scotland. "These can be seen across the UK during midsummer nights. They are estimated to be 70 to 90km (45-55 miles) up in the sky - so high that even at night, they are illuminated by the sun's rays," says Hammond.
Nick Fletcher's photo of Whitby Abbey depicts early summer in North Yorkshire. "Cumulus humulis are among the first types of cloud we see in summer. These form as surface temperatures rise during the morning. On some days, these clouds become large enough to produce a shower - making for a very British summer," says Hammond.
Alan Tyldesley has photographed bands of cirrus and cirrostratus with hints of the distinctive and rare Kelvin-Helmholtz cloud. "They are caused by a strong vertical shear between two air streams. The pattern is produced when the wind blows faster at the upper level than at the lower level," says Hammond.
This foreboding scene, pictured by Richard Robotham, depicts a cumulus fractus under the base of well-developed cumulus clouds. "These can be a sign of showers or longer spells of rain. Take cover!" says Hammond. For more on cloud spotting, see links below.