Wolstanton Scenes

Under Development

Scenes of Wolstanton will appear here when ready!

• Cumulus humilis
• Cumulus mediocris
• Cumulus congestus
• Cumulonimbus
• Special Features

Cumulus humilis

These clouds occur where there is only very slight uplift within a small vertical range.  They occur on otherwise sunny days.  In this case above the cumulus clouds is a high level veil of cirrostratus (which gives the sky a milky appearance), and a mid level stratus cloud (top left).

The photograph shows the estuary of the Afon (river) Ffraw at Aberffraw

Cumulus mediocris

These occur when there is a little more uplift.  They are not big enough to produce rain, but given time and continued growth they can develop into Cumulus congestus.

Each cloud lies within a 'column' of rising air.  The clear air between the clouds is descending.

In the photograph of Perranporth beach, Cornwall, the tops of the cumulus are rather flattened, suggesting that they are having difficulty gaining further height.  This often happens at at a temperature inversion.

The next photo, of Westport Lake, Stoke-on-Trent, was taken on a day of more vigorous cumulus growth.  In this case the clouds show no evidence of flattening at the top.  The picture was taken during the morning, and as the day went on much larger cumulus developed, giving heavy showers.

On both occasions, the cumulus clouds were developing in cool polar maritime air, on a WNW wind, following the passage of a cold front.  This air mass is usually unstable, especially in coastal areas during the winter half of the year, and in inland areas during the summer.

Throughout the year, however, it is associated with good visibility and low levels of air pollution!

Cumulus congestus

By this stage the clouds have reached quite a great height (usually over 3km) and have bright sunlit sharp edges near their summits and dark bases. They can produce showery rain, and occasionally, hail. Although the cloud tops endure temperatures well below zero, the clouds are still formed by minute liquid water droplets. Water still in a liquid state at temperatures below zero Celcius is described as supercooled. At these heights the air is very pure, usually lacking dust particles, salt, etc. Water only freezes at zero Celcius when there particles are present.

Note that the edges of the cloud in the top picture and the one below are sharp. This indicates that the cloud is growing rapidly, and is a sure warning that heavy showers are on the way.

Cumulus clouds can produce some of the most dramatic 'cloudscapes', often causing a marked contrast between light and shade.

In the picture opposite, the sun is hidden behind thick cloud and its rays have been channeled between towering cumulus clouds. Such bright rays of sunlight are described as crepuscular.

They are usually most pronounced when the sun is low in the sky, e.g. towards evening.

As the day draws to a close, convection usually begins to die down.  The sun is no longer heating the surface very much and the rising thermals of air that produce cumulus clouds start to die away.  The clouds fragment and evaporate, often leading to clear skies during the night.

It is during the evening, perhaps, that the most beautiful cumulus skyscapes occur. The bases of the clouds are now hidden from the sun and appear particularly dark, in contrast with the cloud tops which are still sunlit.