Fibratus Cloud Species: Fiberlike, Hairlike

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Definition: A species of cirrus or cirrostratus cloud appearing wispy and fibrous

Description & Characteristics. The ‘fibratus’ cloud species is found in only high-altitude cirrus and cirrostratus cloud types, and is one of only two species that’s associated with cirrostratus clouds. Translated from latin meaning fibered, their cloud abbreviations can be respectively written as ‘Ci fib’ and ‘Cs fib’. They’re a favorite amongst cloudspotters as they have an ethereal appearance, especially when viewed at sunset.

The species is a fairly common occurrence in cirrus clouds. You’re probably more likely to see a fibratus cloud in a cirrus cloud versus a cirrostratus cloud. While cirrostratus generally aren’t accompanied with a lot of detail, they’re sometimes given detail through the fibratus cloud species. The fibratus species can bring out a halo phenomena in both clouds, as they’re composed of ice crystals.

Fibratus clouds might be an indication of a warm front on the horizon, which might mean bad weather. Take that with a grain of salt: they can also be an indication of fair weather as well. It’s not unusual to see the fibratus cloud species paired up with other cirrus cloud varieties, such as duplicatus (multilayered) and radiatus (parallel bands and strips). The cloud varieties cirrus vertebratus and cirrus intortus are more often than not found accompanied with a fibratus classification as well.

As a cloudspotter, know that cirrus uncinus cloud formations are very similar to fibratus clouds, the difference being uncinus clouds have a distinct hook and comma shape in addition to being wispy like the fibratus species. Many times, cirrus fibratus and cirrus uncinus can be seen in the same sky. It’s also possible for cirrus fibratus clouds to be formed from sheared aircraft contrails high up in the atmosphere (cirrus fibratus homomutatus).

Cirrus fibratus (Ci fib)
Cirrus fibratus (Ci fib)
Cirrus fibratus radiatus (Ci fib ra)
A photograph of cirrus fibratus clouds (Ci fib) above a stratocumulus layer

Fibratus Cloud Types

The fibratus cloud species is associated with only two cloud types: cirrus and cirrostratus.

A graphical illustration of a cirrus fibratus cloud

Cirrus (Ci)

High, wispy streaks

A graphical illustration of a cirrostratus fibratus cloud

Cirrostratus (Cs)

Pale, veil-like layer