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Cloud Type Priority

Priority Low-level clouds Mid-level clouds High-level clouds
Highest Cumulonimbus having a clearly fibrous (cirriform top, often anvil shaped, with or without Cumulus, Stratocumulus, Strratus, or scud.
L9
Altocumulus of a chaotic sky, usually at different levels; patches of dense Cirrus usually present also
M9
Cirrocumulus alone or Cirrocumulus with some Cirrus or Cirrostratus, but the Cirrocumulus being the main cirriform cloud
H9
Clouds are ranked according from highest priority to lowest Cumulonimbus with tops lacking clear-cut outlines, but distinctly not cirriform or anvil shaped; with or without Cumulus, Statocumulus, or Stratus
L3
Altocumulus in the form of Cuumulus-shaped tufts or Altocumulus with turrets
M8
Veil of Cirrostratus covering the entire sky
H7
Stratocumulus formed by the spreading out of Cumulus; Cumulus often present also
L4
Doubled-layered Altocumulus, or a thick layer of Altocumulus, not increasing; aoe Altocumulus with Altostratus and/or Nimbostratus
M7
Cirrostratus not increasing and not covering the entire sky
H8
Cumulus and Stratocumulus (not formed by the spreading out of Cumulus) with bases at different levels
L8
Altocumulus formed by the spreading out of Cumulus or Cumulonimbus
M6
Cirrus and Cirrostratus, often in converging bands, or Cirrostratus alone; generally overspreading and growing denser; the continuous layer exceceeding 45° altitude.
H6
Cumulus of considerable development, generally towering, with or without other Cumulus or Stratocumulus, bases all at same level.
L2
Thin Altocumulus in bands or a layer gradually speading over the sky and usually thickening as a whole
M5
Cirrus and Cirrostratus, often in converging bands, or Cirrostratus alone; generally overspreading and growing denser; the continuous layer not reaching 45° altitude
H5
Cumulus of fair weather, little vertical development and seemingly flattened
L1
Thin Altocumulus in patches; cloud elements continually changing and/or occurring at more than one level
M4
Cirrus, often hook shaped, gradually spreading over the sky and usually thickening as a whole
H4
Stratocumulus not formed by spreading out of <strong>Cu</strong>
L5
Thin Altocumulus, mostly semitransparent; cloud elements not changing much and at a single level
M3
Dense Cirrus, often anvil shaped, derived from or associated with Cumulonimbus
H3
Stratus or StratusFractus, but no StratusFractus of bad weather
L6
Thick Altostratus, greater part sufficiently dense to hide sun (or moon), or Nimbostratus
M2
Dense Cirrus in patches or twisted sheaves, usually not increasing, sometimes like the remains of Cumulonimbus; or towers ot tufts.
H2
Lowest StratusFractus and/or CumulusFractus of bad weather (scud)
L7
Thin Altostratus (most of cloud layer semitransparent)
M1
Filaments of Cirrus, or "mares tails," scattered and not increasing.
H1
Often, more than one cloud type occurs in each level (low, mid, or high) in the atmosphere. However, since only one cloud type is indicated for each level, the cloud that is coded is based upon a priority list of the most predominate cloud for each particular level.

At right is a list of priority and symbol for each cloud type. Hold mouse over symbols to reveal cloud type name.

How is this list used? If more than one cloud type exits for any given level, the cloud with the highest priority is plotted. For example, an observer might see a cumulonimbus (L9) and stratocumulus (L5) at the same time. In the list of priorities, only the cumulonimbus (L9) will be plotted.


 Back:  Weather Maps: Cloud Types

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Updated: February 3, 2003
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