Cumulonimbus Pannus

Cumulonimbus pannus clouds are a collection of fractus clouds that form underneath one of the main cloud forms. A fractus cloud is, as the name suggests, fragments of a main cloud that have been broken away, usually by the wind. These fractus clouds can gather in groups underneath the main cloud and this grouping is called a pannus. A pannus can be created under the following clouds:

• Cumulus
• Nimbus
• Stratus

There are lots of variations within each group of clouds and there are also anomalies and special structures too, under which category the pannus clouds fall into.

What height are cumulonimbus pannus clouds found?

As you may know, cumulonimbus clouds develop at around 6,000 feet or less; therefore the pannus will be formed underneath this level, sometimes within a few hundred feet of the earth.

Classification of cumulonimbus pannus clouds

There are no sub-categories of cumulonimbus pannus clouds as they are formed either from the cumulus clouds or nimbus clouds that have parented them.

How are cumulonimbus pannus clouds formed?

Once the sun has warmed the air it will rise into the atmosphere. As the air is cooled in the atmosphere this will cause the water droplets to condense. This action then leads to the creation of a cloud. The different kinds of clouds can be created with a variety of other factors too, not just by warm air. The wind also plays a part and the higher up into the atmosphere the water is allowed to go the less likely it is to create the kind of clouds to make rain, i.e. cumulonimbus clouds. Sometimes the wind is such that it causes parts of the cloud to detach. This forms smaller clouds and a group of smaller clouds are known collectively as a pannus. Therefore, the pannus is not a cloud group created in its own right; it is simply a by-product of a parent cloud.

What do cumulonimbus pannus clouds look like?

The pannus clouds look a little like the main cloud has been shredded or sheared. They are generally observed below the thicker cumulonimbus clouds. Their edges are usually ragged and not rounded as can be seen by their parent clouds. They also will not extend beyond the parent cloud. The pannus clouds may merge if there are sufficient of them to create their own layer. They will be observed quite close to the earth.

How common are cumulonimbus pannus clouds?

Cumulonimbus pannus clouds are common, although pannus clouds are more usually found beneath nimbostratus clouds. However, they are known to accompany other cloud structures too. The bottom or base of the cloud is usually dark and the pannus clouds can usually be seen below this.

Where can I see cumulonimbus pannus clouds?

Cumulonimbus pannus clouds are common all over the world. However, they do depend on the wind to create them and shear them away from the parent cloud, therefore, atmospheric conditions must be correct for them to be created and visible.

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