Cirrus Uncinus

Above: Cirrus Uncinus

Cirrus Uncinus

What are cirrus uncinus clouds?

Cirrus uncinus clouds derive their specific name from Latin. The word “uncinus” in Latin means “curly hooks” and in common parlance, uncinus clouds are identified with reference to what looks like mares’ tails. Normally thinly distributed at higher altitudes, the cirrus uncinus is part of the cirrus family of cloud formations. What makes the cirrus uncinus cloud formations unique is the hooks or curls that commonly appear at the ends of these cloud formation.

What height are cirrus uncinus clouds found?

Similar to other types of cirrus clouds, these are known as high altitude clouds and form when the temperature is between 40 to 50 degrees Celsius. These clouds normally form at about 23,000 feet or more and are classified as high level clouds.

Classification of cirrus uncinus clouds

While there is no specific classification of the cirrus incinus clouds apart from the fact that they form part of the cirrus family, it is possible to identify the cirrus incinus clouds by contrasting them based on specific features:

  • The cirrus incinus clouds have curly hooks at the end as compared to the cirrus fibratus clouds that end as wispy hairs.


  • The cirrus incinus clouds are very sparsely distributed over the sky.


  • The cirrus incinus clouds are commonly visible when there is a warm front coming in and depending on the direction of the wind, the curls or hooks will point outward away from the wind direction.


  • Since these clouds are highly placed, there is usually precipitation which signifies incoming rain, although these are not “rain clouds’ at all.

How are cirrus uncinus clouds formed?

The cirrus incinus clouds may actually be an indication that there is instability in the stratosphere in the context of the amount of moisture as well as the heat moving up from the earth. In addition, this manifestation is also caused by the uncertainty of the wind and consequently, the mares’ tails go in different directions.  These long tails are formed by precipitation as tiny ice crystals fall through the air and when combined with high altitude winds blowing, these ice crystals are spread out forming cirrus incinus. Commonly formed as a consequence of the saturation of air mass in the troposphere and combined with strong winds from below.

What do cirrus uncinus clouds look like?

The cirrus incinus clouds are very distinct and are easily identified. Although they are also fairly thin and wispy clouds, the specific feature is that they have what look like mares’ tails at the end. These may sometimes have contrails running through them. Contrails are lines that appear to cut across these cirrus incinus clouds.

How common are cirrus uncinus clouds?

As part of the cirrus family, the cirrus incinus clouds are very common although they do not appear to impact on the weather generally as they usually evaporate once they reach the lower levels.

Where can I see cirrus uncinus clouds?

These types of cirrus incinus clouds are distributed worldwide.

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