TAF cloud and significant weather groups
- Cloud group: forecast sky, cover code + height.
- Weather group: forecast significant weather.
TAF CYYZ 051130Z 0512/0612 24012KT P6SM FEW040 FM051700 27015G25KT 3SM -SHRA BKN020
Cloud group (FEW040 = few at 4,000 ft AGL; height in hundreds of feet above aerodrome):
- Cover codes as METAR:
SKC/FEW/SCT/BKN/OVC/VV. - Cover rises
FEW<SCT<BKN<OVC. - Thickening and lowering layer: more cover, lower base (
SCT040toBKN020). - Only CB gets a type suffix, e.g.
BKN040CB. VV= obscured sky. Figure is vertical visibility in hundreds of feet, not cloud base.- e.g.
PROB30 2820/2822 1/2SM SN VV005= 30% probability, day 28 2000Z to 2200Z, 1/2 SM visibility, moderate snow, sky obscured, vertical visibility 500 ft.
- e.g.
Significant weather groups:
- Max three per forecast period.
- Several: treated as one entity.
NSW(nil significant weather) marks where forecast weather ends.
Proximity qualifier VC:
| Report | VC means |
|---|---|
| TAF | 5 to 10 NM from centre of runway complex |
| METAR | within 5 SM, but not at the station |
Trap: reading a VV figure as a cloud base, or crossing TAF VC (5 to 10 NM) with METAR VC (within 5 SM).
References
- TC AIM MET 7.3
- TC AIM MET 8.1