If you're unsure which code figure to report use one of our pictorial guides which show the priority of coding.
Low level types (guide)
CL1 Small cumulus CL2 Cumulus of moderate or strong vertical development CL3 Cumulonimbus without anvil CL4 Stratocumulus from spreading out of cumulus CL5 Stratocumulus not from the spreading out of cumulus CL6 Stratus CL7 Stratus fractus and cumulus fractus of bad weather (pannus) CL8 Cumulus and stratocumulus at different heights CL9 Cumulonimbus with anvil
Medium level types (guide)
CM1 Thin altostratus CM2 Thick altostratus or nimbostratus CM3 Semitransparent altocumulus CM4 Altocumulus continually changing shape (Lenticular altocumulus) CM5 Altocumulus progressively invading the sky CM6 Altocumulus from the spreading out of cumulus CM7 Altocumulus with altostratus or nimbostratus (other than chaotic sky) CM7 Thick altocumulus in a single layer CM7 Altocumulus at two or more levels or thick altocumulus in a single layer CM8 Altocumulus with tufts or sproutings CM9 Altocumulus of a chaotic sky
High level types (guide)
CH1 Cirrus in filaments or hooks not progressively invading the sky CH2 Dense cirrus CH3 Dense cirrus from cumulonimbus CH4 Cirrus progressively invading the sky CH5 Cirrostratus increasing but below 45 degree elevation CH6 Cirrostratus increasing and above 45° elevation CH7 Cirrostratus covering the whole sky CH8 Cirrostratus not progressively invading the sky and not entirely covering the sky CH9 Cirrocumulus
Other clouds and phenomenon
Condensation trails Corona Crepuscular rays Halo phenomena Irisation Lightning Mamma Nacreous (mother-of-pearl) clouds Noctilucent clouds Rainbow Smoke Spout Velum/Pileus Virga
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