0 0 OBSERVING RULES FOR BASE OF LOWEST CLOUD AND CLOUD TYPES OF FM 12 SYNOP AND FM 13 SHIP APPLY
1 1 FIRST NON-CUMULONIMBUS SIGNIFICANT LAYER
2 2 SECOND NON-CUMULONIMBUS SIGNIFICANT LAYER
3 3 THIRD NON-CUMULONIMBUS SIGNIFICANT LAYER
4 4 CUMULONIMBUS LAYER
5 5 CEILING
6 6 CLOUDS NOT DETECTED BELOW THE FOLLOWING HEIGHT(S)
7 7 LOW CLOUD
8 8 MIDDLE CLOUD
9 9 HIGH CLOUD
10 10 CLOUD LAYER WITH BASE BELOW AND TOP ABOVE THE STATION
11 11 CLOUD LAYER WITH BASE AND TOP BELOW THE STATION LEVEL
20 20 NO CLOUDS DETECTED BY THE CLOUD DETECTION SYSTEM
21 21 FIRST INSTRUMENT DETECTED CLOUD LAYER
22 22 SECOND INSTRUMENT DETECTED CLOUD LAYER
23 23 THIRD INSTRUMENT DETECTED CLOUD LAYER
24 24 FOURTH INSTRUMENT DETECTED CLOUD LAYER
62 62 VALUE NOT APPLICABLE
63 63 MISSING VALUE
