| Cumulonimbus (CB) and Cumulus congestus (Towering Cumulus: TCU) | |
|---|---|
| ISOL: | Separate CB or TCU with maximum spatial coverage less than 50% of the area concerned. |
| OCNL: | Occasional CB or TCU with maximum spatial coverage of between 50 and 75% of the area concerned. |
| FRQ: | Frequent CB or TCU with maximum spatial coverage greater than 75% of the area concerned. |
| EMBD: | CB (and not TCU) drowned in the cloud mass. |
LYR is used when two or more stratiform cloud types occur at different levels between the base and top of the layer being described.