Mackerel Sky Natural
Amanda Lee Tzafrir
Photograph - Photography
A mackerel sky or buttermilk sky describes a sky mostly covered by altocumulus clouds. It is rare with altocumulus and extremely rare in its cirrocumulus form. The occurence of these clouds is an indicator of moisture and instability at intermediate levels (2400–6100 m, 8000-20,000 ft). Rainshowers or thunderstorms may occur should any lower cumulus clouds reach the layer of the altocumulus form.
However, the most common reason for the occurrence of a mackerel sky is an old, disintegrating frontal system. The cloud was probably originally altostratus and has been broken up into altocumulus as the weather front disintegrates (usually as a result of encountering an area of high atmospheric pressure). Little, if any rain most often follows a mackerel sky. Another common place that it is found is in the warm sector of a depression preceeding the cold front and associated showery weather, however usually here it is obscured by lower stratus clouds.
Mackerel skies are spoken of in the popular bywords, "Mackerel in the sky, three days dry," "Mackerel sky, mackerel sky. Never long wet and never long dry," and the nautical weather rhyme, "Mare's tails and mackerel scales / Make tall ships carry low sails." The phrase 'mackerel sky' came from the fact that it looks similar to the markings of an adult king mackerel.
April 29th, 2013
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