A field guide to Clouds
The ten genera and two curiosities
The ten cloud genera of the WMO cloud atlas, from cirrus high above to stratus near the ground, each drawn at its real height, plus lenticular clouds and mammatus, with what they say about the weather.
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- Cirrus Lock of hair 5–13 km · fair, change ahead
- Cirrocumulus Curl + heap 5–13 km · mostly fair
- Cirrostratus Curl + layer 5–13 km · halo, rain may follow
- Altocumulus High heap 2–7 km · changeable
- Altostratus High layer 2–7 km · rain on the way
- Nimbostratus Rain layer Base < 2 km · steady rain
- Stratocumulus Layer + heap < 2 km · grey, mostly dry
- Stratus Spread out, layer < 2 km · dull, drizzle
- Cumulus Heap Base < 2 km · fair weather
- Cumulonimbus Rain heap Up to 13 km · thunderstorm
- Lenticular Lens-shaped Lee of mountains · strong wind
- Mammatus Udder, breast Under an anvil · storm nearby
Heights for mid-latitudes after the WMO International Cloud Atlas; the gold bar marks each cloud’s level.
Lenticular and mammatus are not genera of their own but a species and a supplementary feature.