0 |  | No CH clouds. | No Cirrus, Cirrocumulus and Cirrostratus. |
1 |  | Cirrus fibratus, sometimes uncinus, not progressively invading the sky. | Cirrus in the form of filaments, strands or hooks, not progressively invading the sky. |
2 |  | Cirrus spissatus, in patches or entangled sheaves, which usually do not increase and sometimes seem to be the remains of the upper part of a Cumulonimbus; or Cirrus castellenus or floccus. | Dense Cirrus, in patches or entangled sheaves, which usually do not increase and sometime seem to be the remains of the upper part of a Cumulonimbus; or Cirrus with sproutings in the form of small turrets or battlements, or Cirrus having the appearance of cumuliform tufts. |
3 |  | Cirrus spissatus cumulonimbogenitus. | Dense Cirrus, often in the form of an anvil, being the remains of the upper parts of Cumulonimbus. |
4 |  | Cirrus uncinus of fibratus, or both, progressively invading the sky; they generally thickens as a whole. | Cirrus in the form of hooks or of filaments, or both, progressively invading the sky; they generally become denser as a whole. |
5 |  | Cirrus (often in bands) and Cirrostratus, or Cirrostratus alone, progressively invading the sky; they generally thicken as whole, but the continuous veil does not reach 45 degrees above the horizon . | Cirrus (often in bands converging towards one point or two opposite points of the horizon) and Cirrostratus, or Cirrostratus alone; in either case, they are progressively invading the sky and generally growing denser as a whole, but the continuous veil does not reach 45° above the horizon. |
6 |  | Cirrus (often in bands) and Cirrostratus, or Cirrostratus alone, progressively invading the sky; they generally thicken as whole, the continuous veil extends more than 45 degrees above the horizon, without the sky being totally covered. | Cirrus (often in bands converging towards one point or two opposite points of the horizon) and Cirrostratus, or Cirrostratus alone; in either case, they are progressively invading thesky and generally growing denser as a whole, the continuous veil extends more than 45° above the horizon, without the sky being totally covered. |
7 |  | Cirrostratus covering the whole sky. | Veil of the Cirrostratus covering the celestial dome. |
8 |  | Cirrostratus not progressively invading the sky and not entirely covering it. | Cirrostratus not progressively invading the sky and not entirely covering the celestial dome. |
9 |  | Cirrocumulus alone, or Cirrocumulus predominant among the CH clouds. | Cirrocumulus alone, or Cirrocumulus accompanied by Cirrus or Cirrostratus, or both, but Cirrocumulus is predominant. |
/ |  | CH clouds invisible owing to darkness, fog, blowing dust or sand, or other similar phenomena or because of continuous layer of lower clouds. | Cirrus, Cirrocumulus and Cirrostratus invisible owing to darkness, fog, blowing dust or sand, or other similar phenomena, or more often because of the presence of a continuous layer of lower clouds. |