Above: Altocumulus


Altocumulus clouds are classified as a middle altitude cloud that can be found at heights of between 2,000 to 7,000 meters. They can be easily spotted thanks to their clumpy or blotchy appearance and they are normally colored from white to a medium grey color.

What are altocumulus clouds?

Altocumulus clouds are found at a mid level between 6,000 and 20,000 feet and they appear to look like beaded or bands of cloud or they are round like cotton wool balls that almost appear to  be stuck to  the deep blue sky above. It is rare but not impossible to see these clouds when there are higher layers of cirrostratus clouds above. They will often form in patterns appearing as bands of clouds slowly progressing across the sky. Should you hold your thumb up raised to the sky, your thumb will be able to obscure an individual altocumulus cloud.

Types of altocumulus clouds

  • Altocumulus castellanus
  • Altocumulus undulatus
  • Altocumulus mamma
  • Altocumulus stratiformis
  • Altocumulus virga
  • Altocumulus lacunosus
  • Altocumulus perlucidus
  • Altocumulus radiatus
  • Altocumulus lenticularis
  • Altocumulus duplicatus
  • Altocumulus undulatus
  • Altocumulus floccus
  • Altocumulus opacus
  • Altocumulus translucidus

How are altocumulus clouds formed?

Altocumulus clouds are made up of water particles that are sucked up from the ground or the sea and carried to higher levels thanks to gentle up winds. Given that they can form at heights from 6,000 feet to altitudes as high as 20,000 feet they can be made up of water particles or ice particles at the higher altitudes. A slow up lift of the water particles creates clouds that are either white or grey if they are denser.

Altocumulus clouds can be as much as 1 kilometer thick and will appear grey in color. When you can see altocumulus clouds you should be aware that a cold front is moving in to replace warmer weather and you can expect bad weather or at least cloudy conditions to arrive within the next 24 to 48 hours.    

What height are altocumulus clouds found?

Altocumulus clouds can be found in the middle-level altitudes that are between 6,000 to 20,000 feet, they can be a much as 1 kilometer in thickness, and they are transitory clouds that will only be seen for a number of hours, rarely for days. They signify a change in the weather, and indicate that a cold front is closing in normally resulting in subsequent thunderstorms in spring or summer or a rain front in autumn and winter that will rapidly clear as the cold front with its associated weather sets in.   

How common are altocumulus clouds?

Altocumulus clouds are very common and can be found anywhere where there are hills or mountains in their vicinity. As they are found at relatively high altitudes, they are not affected by thermal updrafts and they are not susceptible to the weather conditions that form the lower level cumulus nimbus clouds, nor do they produce such dramatic results in the form of thunderstorms in spring and summer time or heavy downpours in the autumn or winter.

The most common locations to find altocumulus clouds:   

  • Worldwide; they can be found in any part of the globe.
  • These clouds are found whenever there are high hills or mountains.
  • They can appear when cold fronts are moving in and brief periods of bad weather can be expected.

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