Cloud Types and Forecasting Using Clouds

This is just a basic guide of the different cloud types that we see in our skies and what they consist of. I will cover the 10 cloud types and how they can sometimes be used as forecasting tools. I have broken the cloud types into low level clouds, mid level clouds and high level clouds for easy reference

Low Level Clouds
The 4 basic low level clouds occur from 0 to approx 7000ft (can be higher in warm climates eg tropics) They consist of water in liquid form and are the main clouds in which rain forms.

Cumulus- Cumulus clouds can appear as small bundles of cotton wool with nice flat bases or can appear as towering monsters appearing like huge cauliflowers. If the air is stable smaller cumulus cells will form. Large cumulus cells indicate that there is strong convective current/ or turbulence and asre a good indicator that bad weather is possible. Large Cumulus clouds can produce showers of rain and if there is enough heating, may turn into cumulonimbus

Fine weather cumulus links
www.cloudappreciationsociety.org...

Convective Cumulus links
www.cloudappreciationsociety.org...

Cumulonimbus- Cumulonimbus clouds are more commonly known as thunderstorm clouds. These monsters can sometimes reach as high as 40,000ft (higher in the tropics) and are the ultimate in convective cloud formations. They form when multiple air layers are unstable all the way up to the tropopause. Cumulonimbus clouds have a characteristic anvil shaped top and can produce heavy rain, hail, snow and can kick up dust

Cumulonimbus links
www.cloudappreciationsociety.org...

Stratus- Stratus clouds occur lower then any of the other clouds. They are characterised by there dull dark colour and sometimes can cover the whole sky and occasionally produce drizzle. They also form below Cumulonimbus clouds often appearing as a "scud cloud". Stratus also forms below temperature inversions near high pressure systems, so instead of a nice fine sunny day (expected with high pressure systems), you may have a gloomy stratus filled day instead.

Stratus links
www.cloudappreciationsociety.org...

Stratocumulus- Stratocumulus is similar to stratus except it occurs higher and has a lumpy appearance. It can occur under temperature inversions associated with high pressure and can cover the entire sky. Occasionally it produces rain or drizzle (rare though) and is an unreliable forecasting tool.

Stratocumulus links
www.cloudappreciationsociety.org...

Mid Level Clouds
There are three basic mid level clouds. They too can produce precipitation like low level clouds. They consist of what is called super cooled water droplets which is water existing as liquid below freezing point. The occur at a height of 7000ft to 20,000ft

Nimbostratus- Nimbostratus is the true rain cloud. Unlike other clouds, nimbostratus can occur as a low level cloud or a mid level cloud. It is a dark layer of cloud that most comonly covers the whole sky and produces continuos rain. It is formed from the thickening out of altostratus clouds which occur higher up. As the air becomes moister the cloud becomes heavier and descends and thickens as it falls

Nimbostratus links
www.cloudappreciationsociety.org...

Altostratus- Altostratus can be either a thick light grey (can be semi transparent) layer or a dark grey opaque cloud. It can also appear in large patches. It is a good indicator of stable weather but occasionally may produce rain

Altostratus link
www.cloudappreciationsociety.org...

Altocumulus- Altocumulus occurs when the mid levels are unstable, giving it a lumpy appearance. It can take many forms from the tufts and turrets of altocumulus castellanus to the "ufo shaped" lenticularis clouds or the beautiful sky covering altocumulus perlucidus.

Altocumulus links
www.cloudappreciationsociety.org...

www.cloudappreciationsociety.org...

www.cloudappreciationsociety.org...

High Level Clouds
These clouds occur above 20,000ft and consist of ice crystals. They can indicate anything from the approach of cold fronts or thunderstorms. Contrails produced by aircraft are known as cirrus clouds if they persist for half an hour

Cirrus- Cirrus can appear in several forms. It is a good indicator of high level mositure and occasionally instability. It can appear as a thin wispy patch, in thick twisted masses, as thin hooks or as a thick anvil shaped mass at the top of thunderclouds

Cirrus links
www.cloudappreciationsociety.org...

www.cloudappreciationsociety.org...

www.cloudappreciationsociety.org...

Cirrostratus- Cirrostratus can form at the front of cold and occluded fronts and is a good indicator of a moist (but stable) upper air environment. Hence it is a good precursor to rain, esepcially if it spreads across the sky. It is so reliable a tool that rain can be forecast up to a day in advance. It can also be formed by the spreading out of cirrus. It regularly cover the whole sky and regularly produces different halo phenomenen. Sometimes it can be so thin that its invisble to the naked eye

Cirrostratus link
www.cloudappreciationsociety.org...

www.cloudappreciationsociety.org...

Cirrocumulus- Cirrocumulus is formed when upper levels are unstable giving its puffy cellular appearance and is rarer then the other high level clouds. It can cover the entire sky and sometimes forms what is known as a "mackeral sky".

Cirrocumulus link
www.cloudappreciationsociety.org...

Any questions ask away

Thanks to the cluoud appreciation society for the pictures
www.cloudappreciationsociety.org...



[edit on 30/4/2008 by OzWeatherman]