CAA NZ CPL Meteorology cheat sheet

METAR: routine aerodrome observation issued at half-hourly or hourly intervals; SPECI is issued when a significant change to the reported conditions occurs between routine reports.

TAF: aerodrome forecast valid for a stated period, typically 24-30 hours at international aerodromes; TEMPO and BECMG groups describe temporary fluctuations and permanent changes respectively.

TAF amendment indicators: AMD denotes an amended forecast; COR denotes a corrected forecast issued to fix an error; both replace the previously issued TAF.

TREND: a 2-hour (or 3-hour where specified) forecast appended to a METAR/SPECI, using BECMG, TEMPO or NOSIG; NOSIG means no significant change expected.

GRAFOR: graphical area forecast for NZ, issued for the low-level airspace in fixed time blocks; depicts cloud, weather, visibility, turbulence and freezing level by region.

SIGMET: issued for phenomena hazardous to all aircraft - severe turbulence, severe icing, volcanic ash, tropical cyclone, severe mountain waves; valid 4 hours (6 hours for volcanic ash).

AIRMET: issued for moderate hazards affecting low-level aircraft (moderate turbulence, moderate icing, mountain obscuration, widespread visibility below 5 km); valid 6 hours.

AIREP/SPECI AIREP: pilot reports of actual conditions; AMDAR provides automated aircraft-derived wind and temperature data for model input and forecast verification.

VOLMET and ATIS provide continuous broadcast weather; ATIS carries aerodrome observations and trend, VOLMET carries METAR/TAF for en-route reception.

Wind group 24015G28KT: direction 240° true, mean speed 15 kt, gusting to 28 kt; VRB indicates variable direction with no meaningful mean; 00000KT means calm.

Visibility: 9999 means 10 km or more in METAR; four-digit groups below 5000 are metres; RVR reported as Rxx/xxxx in metres with D/U for decreasing/increasing trend.

Cloud: FEW (1-2 oktas), SCT (3-4), BKN (5-7), OVC (8); the first BKN/OVC layer defines ceiling; NSC means no significant cloud, NCD means no cloud detected automatically.

Weather codes: intensity prefix + (heavy) or - (light); SH showers, TS thunderstorm, FZ freezing, GR hail, GS small hail, BL blowing, DR drifting, MI shallow, BC patches.

Temperature/dewpoint spread: a spread of 2°C or less indicates high probability of fog or low cloud; QNH below 1013 hPa generally indicates low pressure with associated poor weather.

CAVOK: visibility 10 km or more, no cloud below 5000 ft or below the highest MSA whichever is greater, and no significant weather; replaces visibility, cloud and weather groups.

Colour codes in NZ: GRN (no cloud below 1500 ft, visibility 8 km or more), YLO, AMB, RED, BLK; BLACK denotes aerodrome closed due to weather.

Icing and turbulence severity: report as light, moderate, severe; severe means aircraft handling is seriously affected or structural damage possible - avoid the area.

Freezing level and 0°C isotherm: above the freezing level, visible moisture can produce airframe icing; supercooled large droplets (SLD) below -20°C increase risk significantly.

NZ meteorological service for aviation is provided under Part 174 (Meteorological Service Organisations - Certification); the certified provider is MetService.

Pilot responsibilities: obtain a pre-flight weather briefing appropriate to the route, and update in flight when conditions differ or forecasts become invalid.

METAR/SPECI are observation products; TAF, GRAFOR, SIGMET, AIRMET are forecasts/warnings - a pilot must not treat a TAF as an observation.

SIGMET must be issued for volcanic ash, tropical cyclone, severe turbulence, severe icing, severe mountain waves and other phenomena hazardous to all aircraft.

Aerodrome forecasts for NZ international aerodromes are issued with a validity of not less than 24 hours and are amended when conditions differ significantly from forecast.

Flight in known icing conditions is prohibited unless the aircraft is certificated and equipped for it; icing forecasts and AIRMET/SIGMET icing warnings inform the decision.

VFR minima: cloud ceiling and visibility requirements vary by airspace class; meteorological information must be obtained before flight and used to determine whether VFR can be maintained.

ACAS/TAF amendment: when a TAF is amended, the amendment supersedes previous versions; pilots should re-check forecasts before departure and at intermediate stops.

Occurrence reporting: significant weather encounters (severe turbulence, icing, windshear, volcanic ash) should be reported to ATS for onward transmission as AIREP and possible SIGMET.

New-generation satellite (Himawari) provides high temporal resolution imagery (10-minute full disk, 2.5-minute target area) useful for convective and fog monitoring.

Numerical weather prediction ensembles (e.g. ECMWF, GFS, UKMO) give probabilistic guidance; spread between members indicates forecast confidence.

Graphical area forecasts (GRAFOR) replace text area forecasts in NZ, providing gridded depiction of cloud, weather, visibility, turbulence and freezing level.

AMDAR and Mode-S EHS provide automated aircraft observations of wind and temperature, improving model initialisation and short-term forecasts.

Nowcasting uses radar, satellite and surface observations to forecast out to 6 hours; useful for convective and fog evolution.

WAFS provides global gridded forecasts of upper winds/temperatures and significant weather for flight planning; ICAO WAFS is being upgraded to include turbulence and icing grids.

Volcanic ash advisory centres (VAAC) issue ash advisories; Wellington VAAC covers the NZ region; SIGMET for volcanic ash is mandatory when ash is present.

Wind shear and microburst detection: low-level wind shear alert systems (LLWAS) and terminal Doppler weather radar (TDWR) provide warnings at major aerodromes.

Space weather and GNSS: ionospheric disturbances can degrade GNSS and HF communications; advisories are issued for significant events.