ICAO Annex 3, MET Service Provision, and Air Navigation Regulation
Core concepts
Know ICAO Annex 3 provisions: METAR, SPECI, TAF, TREND, SIGMET, AIRMET, and the area forecasts (GAMET). Understand the roles of the meteorological watch office, the world area forecast system, and the tropical cyclone and volcanic ash advisory centres. Study the criteria for issuing SIGMET (severe turbulence, icing, volcanic ash, tropical cyclones) and the format of coded messages. Know the Brazilian DECEA regulations and the responsibilities of the meteorologist.
Traps
Questions often confuse SIGMET with AIRMET and the validity periods of TAF. Be careful with the change groups (BECMG, TEMPO) and their time conventions. Do not confuse QNH with QFE in the context of altimeter setting.
Worked example
A SIGMET for volcanic ash must be issued when ash is reported or forecast in the flight information region. The message includes the phenomenon, the affected area, flight levels, and the validity period. A TAF, by contrast, covers aerodrome forecasts for 9–30 hours depending on the category.