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Coding instructions CM

(Section 2.8.3.2)
  1. If Altocumulus of a chaotic sky is present, the coding is CM = 9
  2. If Altocumulus castellanus or floccus is present, the coding is CM = 8
  3. If Altocumulus is coexisting with Altostratus or Nimbostratus, the coding is CM = 7
  4. If Altocumulus cumulogenitus or cumulonimbogenitus is present, the coding is CM = 6
  5. If Altocumulus is progressively invading the sky, the coding is CM = 5
  6. If Altocumulus patches are continuously changing, the coding is CM = 4
  7. If Altocumulus (of the variety translucidus and/or opacus) are at two or more levels, the coding is CM = 7
  8. If Altocumulus at a single level is predominantly translucidus, the coding is CM = 3
  9. If Altocumulus at a single level is predominantly opacus, the coding is CM = 7
  10. If the greater part of Altostratus is semi-transparent, the coding is CM = 1
  11. If the greater part of Altostratus is dense enough to hide the Sun or Moon completely or if there is Nimbostratus, the coding is CM = 2
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The text enclosed in grey-shaded boxes, like this example, comprises Annex I to the Technical Regulations (WMO-No. 49) and has the legal status of standard practices and procedures.

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