Low Cloud Classifications
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• Low Clouds:
Stratocumulus, Stratus, Cumulus and Cumulonimbus
1
1 is the highest priority and 7 is the lowest priority in designating CL
if more than one type is present.
CL
Code
Priority1
Nontechnical
Cloud Type Description
0
7
No Stratocumulus,
Stratus, Cumulus, or Cumulonimbus.
1
(small Cu)62
Cumulus
with little vertical extent and seemingly flattened, or ragged Cumulus
other than of bad weather3,
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)62
Stratocumulus
not resulting from the spreading out of Cumulus.
6
(St)62
Stratus
in a more or less continuous sheet or layer, or in ragged shreds, or both,
but no stratus fractus of bad weather3
7
(Fs)62
Stratus
fractus of bad weather3 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.
2 If no CL 2, 3, 4, 8 or 9 is present, priority is determined by whatever type has the greatest sky cover.
3 "Bad weather" denotes the conditions that generally exist during precipitation and a short time before and after.
Scientific contact:
Professor Sandra Yuter, Project
Science Coordinator