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Varieties

Duplicatus: Superposed cloud patches, sheets or layers, at slightly different levels, sometimes partly merged.

Intortus: Cirrus, the filaments of which are very irregularly curved and often seemingly entangled in a capricious manner.

Lacunosus: Cloud patches, sheets or layers, usually rather thin, marked by more or less regularly distributed round holes, many of them with fringed edges. Cloud elements and clear spaces are often arranged in a manner suggesting a net or a honeycomb.

Opacus: An extensive cloud patch, sheet or layer, the greater part of which is sufficiently opaque to mask completely the sun or moon.

Perlucidus: An extensive cloud patch, sheet or layer, with distince but sometimes very small spaces between the elements. The spaces allow the sun, the moon, the blue of the sky or over-lying clouds to be seen.

Radiatus: Clouds showing broad parallel bands or arranged in parrallel bands, which, owing to the effect of perspective, seem to converge towards a point on the horizon or, when the bands cross the whole sky, towards two opposite points on the horizon, called "radiation point(s)."

Translucidus: Clouds in an extensive patch, sheet or layer, the greater part of which is sufficiently translucent to reveal the position of the sun or moon.

Undulatus: Clouds in patches, sheets or layers, showing undulations. These undulations may be observed in fairly uniform cloud layers or in clouds composed of elements, separate or merged. Sometimes a double system of undulations is evident.

Vertebratus: Clouds, the elements of which are arranged in a manner suggestive of vertebrae, ribs, or a fish skeleton. The term applies mainly to cirrus.