Mackerel sky

From Wikipedia, the free encyclopedia
  (Redirected from Altocumulus mackerel sky)
Jump to navigation Jump to search
Mackerel sky
Mackerelskylincolnshire.jpg
Altocumulus mackerel sky
Abbreviation Ac
Symbol CM 8.png
Genus Alto- (mediumhigh)
-cumulus (heaped)
Appearance Clumps and rolls of clouds that resemble mackerel scales
Precipitation cloud? No, but may signify approaching precipitation.

A mackerel sky is a common term for a sky with rows of cirrocumulus or altocumulus clouds displaying an undulating, rippling pattern similar in appearance to fish scales;[1][2] this is caused by high altitude atmospheric waves.[3]

Cirrocumulus appears almost exclusively with cirrus some way ahead of a warm front and is a reliable forecaster that the weather is about to change.[4] When these high clouds progressively invade the sky and the barometric pressure begins to fall, precipitation associated with the disturbance is likely about 6 to 12 hours away. A thickening and lowering of cirrocumulus into middle-étage altostratus or altocumulus is a good sign the warm front or low has moved closer and it may start raining within less than six hours.[5] The old rhymes "Mackerel sky, not twenty-four hours dry"[3] and "Mares' tails and mackerel scales make lofty ships to carry low sails"[6] both refer to this long-recognized phenomenon.

Other phrases in weather lore take mackerel skies as a sign of changeable weather. Examples include "Mackerel sky, mackerel sky. Never long wet and never long dry", and "A dappled sky, like a painted woman, soon changes its face".[4]

It is sometimes known as a buttermilk sky, particularly when in the early cirrocumulus stage, in reference to the clouds' "curdled" appearance.[7] In France it is sometimes called a ciel moutonné (fleecy sky); and in Spain a cielo empedrado (cobbled sky);[8] in Germany it is known as Schäfchenwolken (sheep clouds), and in Italy the clouds are known as a pecorelle (little sheep).

In culture[edit]

Peter Paul Rubens' A View of Het Steen in the Early Morning (c.1636) features the first convincing depiction of a mackerel sky in art.

"Ole Buttermilk Sky" by Hoagy Carmichael was nominated for an Academy Award for Best Original Song in 1946.

Gallery[edit]

References[edit]

  1. ^ Downing, L. L. (2013). Metereology of Clouds. p. 154. 
  2. ^ Ahrens, C. Donald; Henson, Robert (2015). Metereology Today. Cengage Learning. p. 153. 
  3. ^ a b Wong, Chi-wai. "Mackerel sky, not twenty-four hours dry". Hong Kong Observatory. 
  4. ^ a b "Ontario Regional Marine Guide". Environment Canada. Archived from the original on 2015-12-03. 
  5. ^ "Mackerel sky". Weather Online. Retrieved 21 November 2013. 
  6. ^ "Making heads of mares' tails". NASA Earth Data. 
  7. ^ Klocek, Dennis (2010). Climate: Soul of the Earth. SteinerBooks. p. 32. 
  8. ^ Hamblyn, Richard (2011). The Invention of Clouds: How an Amateur Meteorologist Forged the Language of the Skies. Pan Macmillan. p. 240.