Aerodrome observations: METAR, SPECI & RVA
| Report | What | Timing |
|---|---|---|
| METAR | Routine aerodrome observation | Every hour on the hour; over 200 Canadian aerodromes |
| SPECI | Special observation, same format as METAR | Between hourly METARs; triggers in speci-criteria |
- Neither hand-encoded: computer builds coded report, staffed or automatic site.
- Not every station reports 24 h/day; check CFS for schedule.
SPECI:
- Triggered by significant change, not by clock.
- Report time = when change happened, not when transmitted.
- Extra observation between METARs: check observation if no significant change, SPECI if change.
- Other triggers: request from forecast centre or ATS, notification of aircraft accident, local criteria set by service provider (MET 8.3.2.2 (a)-(e)).
RVA (MET 1.2.8): runway visibility assessment where no RVR sensor: valid only 20 min.
Trap: SPECI is an observation, not a forecast, fired by change in conditions, not at a fixed time.
References
- TC AIM MET 8.0 (METAR, SPECI, METAR AUTO)
- TC AIM MET 1.2.7 (Usability of Weather Reports)
- TC AIM MET 1.2.8 (Runway Visibility Assessment)
- TC AIM MET 8.3.2.2 (Check and Special Observations)