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9.14 Clouds and Precipitation

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Reporting Cloud Cover

Cloud cover observations have been made by observers, dividing the sky into 8 regions or okta. An okta is a unit of measurement used to describe cloud cover. Sky conditions are estimated in terms of how many eighths of the sky are obscured by cloud, ranging from completely clear, 0 oktas, through to completely overcast, 8 oktas.

Using this frame work, an observer decides whether each sky region contains cloud, and reports cloud cover in OKTAS; e.g. 0 OKTAS = clear sky and 8 OKTAS = overcast sky. The present cloud cover is reported over a 30 minute window that has been extrapolated from fractional readings and reported as “clear”, “few”, “scattered”, “broken” and “overcast” clouds.

  • FEW 1 to 2 OKTAS (Few)
  • SCT 3 to 4 OKTAS (Scattered)
  • BKN 5 to 7 OKTAS (Broken)
  • OVC 8 OKTAS (Overcast)