SIGWX CB symbol, coverage and cloud depiction
Cloud depiction (TC AIM MET 12.2):
| Element | Depiction |
|---|---|
| Type | conventional abbreviation |
| Amount | BKN or OVC |
| Base and top heights | given alongside |
Other abbreviations:
| Abbrev | Meaning |
|---|---|
| LYR | layers |
| CLR | clear |
CB symbol marks thunderstorms occurring or forecast:
- over a widespread area
- along a line
- embedded in other cloud layers
- concealed by a hazard
CB coverage, by area:
| Label | Meaning | Area |
|---|---|---|
| ISOL | isolated | under 50% |
| OCNL | occasional | 50 to 75% inclusive |
| FRQ | frequent | over 75% |
- Embedded CB labels:
ISOL embedded CB,OCNL embedded CB,FRQ embedded CB,FRQ CB - Other cloud: OKTA amount plus cloud type
- Icing and hail: never plotted separately. Chart label: CB symbol implies hail, moderate-or-greater turbulence, icing.
- XXX: on the side of the dividing line where cloud tops or bases exceed chart upper or lower limit.
Trap: CB coverage words are not the SIGMET/AIRMET/GFA percentages; ICAO's SIGWX definitions run 25% higher (their SCT means 25 to 50%).
References
- TC AIM MET 12.2