C_L6 Stratus

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Gallery
© R.K. Pilsbury	© R.K. Pilsbury
© C.S. Broomfield	© F. Norton
© C.S. Broomfield	© C.S. Broomfield (Crown copyright)

Stratus most commonly occurs as a grey, fairly uniform, featureless, single layer of low cloud. Occasionally it can be dark or threatening, although at most it can only produce weak precipitation. This feature makes it fairly easy to distinguish it from nimbostratus, which nearly always produces rain, snow or ice pellets. However, precipitation falling from a higher cloud through a dark, uniform layer of stratus may cause the observer some confusion. Stratus when forming or dissipating may appear as ragged shreds called stratus fractus. When occurring alone, these shreds appear grey when viewed towards the sun and white when viewed away from the sun. Stratus fractus may also appear beneath a continuous layer of stratus. These shreds, unlike those of C_L7, are not accompanied by precipitation. Fog will often lift into a layer of stratus by an increase in wind or a rise in temperature.

Stratus is sometimes comparatively thin and the disc of the sun or moon may be seen with a clear outline (top left photograph).

The top right photograph shows a patch of stratus almost resting on the headland 462 ft above mean sea level. In the middle left photograph the top of an 180 ft high office block is lost to view in low stratus on an overcast foggy morning. Patches of stratus beneath a main layer are seen at middle right. Bottom left shows stratus in a hilly region, base less than 50 feet above ground, having drifted in from the sea. A layer of stratus in the process of dissipation is shown at bottom right, the base of cloud estimated to be 900 ft.

Classification
Description: Stratus in a layer or in ragged shreds but not associated with precipitation.	Designation: CH=6 (C7)
	Latin name: Stratus nebulosus (St neb) or Stratus fractus (St fra).

Related pages: Cloud classification | C_L guide | C_M guide | C_H guide | Cloud index