Low Cloud Classifications

Total Cloud Amounts

Low Cloud Classifications

Middle Cloud Classifications

High Cloud Classifications

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Cl Code Priority (*) Nontechnical Cloud Type Description
0 7 No Stratocumulus, Stratus, Cumulus, or Cumulonimbus.
1 (small Cu) 6 (**) Cumulus with little vertical extent and seemingly flattened, or ragged Cumulus other than of bad weather (***), or both.
2 (Cu) 5 Cumulus of moderate or strong vertical extent, generally with protuberances in the form of domes or towers, either accompanied or not by other Cumulus or by Stratocumulus, all having their bases at the same level.
3 2 Cumulonimbus the summits of which, at least partially, lack sharp outlines, but are neither clearly fibrous (cirroform) nor in the form of an anvil; Cumulus, Stratocumulus, or Stratus may also be present.
4 3 Stratus from the spreading out of Cumulus; Cumulus may also be present.
5 (Sc) 6 (**) Stratocumulus not resulting from the spreading out of Cumulus.
6 (St) 6 (**) Stratus in a more or less continuous sheet or layer, or in ragged shreds, or both, but no stratus fractus of bad weather (***)
7 (Fs) 6 (**) Stratus fractus of bad weather (***) or Cumulus fractus of bad weather, or both (Pannus), usually below altostratus or nimbostratus.
8 (Cu-under-Sc) 4 Cumulus and Stratocumulus other than that formed from the spreading out of Cumulus; the base of the Cumulus is at a different level than that of the Stratocumulus.
9 1 Cumulonimbus, the upper part of which is clearly fibrous (cirroform), often in the form of an anvil, either accompanied or not by Cumulonimbus without anvil or fibrous upper part, by Cumulous, Stratocumlus, Stratus, or Pannus.
/ ?? Stratocumulus, Stratus, Cumulus and Cumulonimbus invisible owing to darkness, fog, blowing dust or sand or other similar phenomena.

(*) 1 is the highest priority and 7 is the lowest priority in designating Cl if more than one type is present.

(**) If no Cl 2, 3, 4, 8 or 9 is present, priority is determined by whatever type has the greatest sky cover.

(***) "Bad weather" denotes the conditions that generally exist during precipitation and a short time before and after.

Edit-Design Center edc(at)atmos.washington.edu