Altocumulus Clouds: Mid-altitude Cloud Heaps
Definition: Middle-altitude cumuliform clouds often arranged in heaps or rolls
Description & Characteristics. Altocumulus clouds are typically found in groups or heaps clumped together. They’re found in the middle layer of the troposphere, lower than cirrocumulus and higher than their cumulus and stratocumulus counterparts. The term mackerel sky is also common to altocumulus (and cirrocumulus) clouds that display a pattern resembling fish scales. Of all the ten different cloud types, you’ll probably find that altocumulus clouds are the one of the most diverse and dynamic in terms of appearance.
These clouds can take on a handful of shapes and sizes. They can include cloud heaps that resemble towering castles (castellanus cloud species), can sometimes resemble a lock of wool (cloud species floccus), can cover the entire sky on occasion (stratiformis cloud species), and can even create horizontal tube-like structured clouds (volutus cloud species).
Altocumulus are also known for creating UFO-shaped clouds (lenticularis cloud species), are responsible for a lot of the fallstreak hole sightings (i.e. hole punch clouds) you might be lucky enough to see (cavum cloud feature), and on the rarest of occasion, can produce a wavy, chaotic appearance (asperitas cloud feature).
Altocumulus Cloud Facts
Cloud Level (Étage): Middle
Altitude/Height: 2-7km (7,000-23,000 ft)
Latin Term: Derives from alto-, meaning high, and cumulo-, meaning heap
Abbreviation: Altocumulus can be abbreviated as Ac
Cloud Color: White to Gray
Precipitation Potential: Virga only
Sky Cover: Mostly cloud to mostly sunny
Cloud Frequency: Very common
Altocumulus Cloud Species
Altocumulus clouds have five associated cloud species: castellanus, floccus, lenticularis, stratiformis, and volutus.
Rising towers, turrets
Puffy, ragged tufts
Lens-shaped, resembling a UFO
Horizontal, layer-like form
Tube-shaped roll cloud
Altocumulus Cloud Varieties
Altocumulus clouds have seven associated cloud varieties: duplicatus, lacunosus, opacus, perlucidus, radiatus, translucidus, and undulatus.
Multilayered
Perforated, round frayed holes
Opaque, masks the sun
Transparent by small gaps
Parallel bands and strips
See-through, sun’s position visible
Wavelike, undulating
Altocumulus Cloud Supplementary Features
Altocumulus clouds have five supplementary features: asperitas, cavum, fluctus, mamma, and virga.
Chaotic, wavy underneath
Fallstreak hole, hole punch
Kelvin-Helmholtz waves, curls
Sac-like, resembling cow udders
Evaporating rain strips
Altocumulus Cloud Accessories & Other Clouds
Altocumulus clouds don’t have any associated accessory clouds or other clouds associated with this cloud type. ⛅
Similar Cloud Types
While altocumulus and altostratus clouds are found at the same altitude, altostratus clouds are generally a featureless layer, where altocumulus clouds typically have plenty of features. Altostratus clouds don’t have any cloud species associated with them, so if you’re deciding between an altostratus and altocumulus cloud and the cloud you’re observing looks to have an associated cloud species, you should learn towards an altocumulus cloud.
Altocumulus vs. Altostratus
Altocumulus and cirrocumulus clouds share many of the same cloud species, but cirrocumulus clouds are higher in altitude, so their cloudlets appear smaller. Cirrocumulus clouds are more often than not seen with cirrus and cirrostratus clouds in near proximity. Altocumulus clouds are also more commonly observed than cirrocumulus. It’s more common to see the entire sky covered by a layer of altocumulus clouds than cirrocumulus clouds.
Altocumulus vs. Cirrocumulus
Altocumulus clouds are generally seen as patches of clouds grouped together, either in rolls, sheets or heaps. Cumulus clouds are more often seen as individual clouds. Cumulus clouds are also much closer to the ground. A key reminder trying to determine the difference between cumulus and altocumulus clouds are that the two cloud types don’t have any shared cloud species.
Altocumulus vs. Cumulus
Altocumulus clouds are more closely related to stratocumulus clouds than they are to cumulus clouds. They share almost all of the same cloud species, cloud varieties, and other cloud features. Their altitude however differentiates them the most, with stratocumulus clouds being closer to the ground. Hence, stratocumulus cloud formations are seemingly bigger, and are generally a bit darker than altocumulus clouds.