Cumulonimbus Pileus

Above: Cumulonimbus Pileus

Cumulonimbus Pileus

Commonly known as a scarf cloud or a cap cloud, a cumulonimbus pileus cloud is a cute little cloud that really doesn't have the full scary impact of the cumulonimbus cloud, even though it is still technically considered one because it actually produces some precipitation.

What is a cumulonimbus pileus cloud?

Known as a scarf cloud or cap cloud, the cumulonimbus pileus cloud is a small horizontal cloud that is not very puffy and not very fibrous either. It is just sort of there. It hoods a cumulus cloud and signifies the beginning of a storm, but is not threatening at this very young level. It can be thought of in general as a baby storm cloud, or a warning label.

What height are cumulonimbus pileus clouds found?

These clouds are found directly at the top of cumulus clouds, so they are at the same level as a cumulus cloud. This can be a wide variety of heights, but is usually not incredibly low in the sky.

Classification of cumulonimbus pileus clouds

Even though this is not usually thought of as a storm cloud, the cumulonimbus pileus cloud is still technically considered a cumulonimbus cloud because it does in fact produce some precipitation. It is a sort of precursor to a storm cloud.

How do cumulonimbus pileus clouds form?

When strong updrafts begin to occur on moist air that is fairly low in the sky, this particular kind of cloud appears at the top of a cumulus cloud. This cloud usually comes at the beginning of a storm right when the air starts to cool down and can produce some minor precipitation before it disappears.

What do cumulonimbus pileus clouds look like?

The nickname for this particular type of cloud is very accurate to the appearance of this cloud. It really looks as if the cumulus cloud in the sky is wearing a funny little hat or a scarf. Besides that, cumulonimbus pileus clouds portray such visual features:

  • These clouds tend to be smooth and smooth-edged, but not very specific in shape.


  • They are actually very fleeting and tend to change shape quickly. You may look one moment and it may seem like a beret, and then next may be closer to a cowboy hat.

How common are cumulonimbus pileus clouds?

Early in the storm cycle, the cumulonimbus pileus cloud is actually pretty common, although catching a glimpse of one may take some watching because they can change and move quickly. They are common, but very short in lifespan.

Where can I see cumulonimbus pileus clouds?

Catching a glimpse of a cumulonimbus pileus cloud may not be an easy thing to do. You have to look at a very specific time. If you feel the air cool down and it seems as if a storm is coming, look up at the cumulus clouds in the sky.  If any of them look like they are wearing a hat, then you have found one of these clouds. Watch closely though, because it will most likely change shape before your eyes.

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