METAR & TAF Weather Codes
Aviation Terminology & Decoders · 4 specs
Direct Answer
Aviation weather reports use concise international shorthand: METAR (Meteorological Aerodrome Report) transmits hourly routine surface observations, while TAF (Terminal Aerodrome Forecast) provides 24- to 30-hour airport weather forecasts covering winds, visibility, clouds, and weather hazards.
Specs
| Format Standard | WMO Manual No. 782 / ICAO Annex 3 (Meteorological Service for International Air Navigation) |
| METAR Frequency | Issued every 30 to 60 minutes (or SPECI for urgent significant changes) |
| TAF Validity | Published every 6 hours, valid for 24 or 30 hours |
| Time Standard | All timestamps formatted in Coordinated Universal Time (UTC / 'Z' Zulu time) |
Anatomy of a METAR Weather String
A standard METAR string reads systematically from left to right:
METAR KJFK 251651Z 31015G25KT 10SM -RA BKN040 OVC090 18/12 A2992 RMK AO2 SLP131
KJFK: ICAO Station Identifier (New York JFK).251651Z: Day 25 at 16:51 UTC (Zulu).31015G25KT: Winds from 310° true at 15 knots, gusting to 25 knots.10SM: Visibility 10 Statute Miles (CAVOKin Europe = Ceiling and Visibility OK).-RA: Light Rain (-light, no prefix moderate,+heavy).BKN040 OVC090: Broken clouds at 4,000 ft AGL, Overcast at 9,000 ft AGL.18/12: Temperature 18°C / Dewpoint 12°C.A2992: Altimeter setting 29.92 inHg (orQ1013in hPa/millibars).
WMO / ICAO Weather Phenomena & Descriptor Matrix
| Code | Meaning / Weather Phenomenon | Meteorological Category | Operational Impact |
|---|---|---|---|
| DZ | Drizzle | Precipitation | Minor visibility reduction, slick surfaces |
| RA | Rain | Precipitation | Runway wetness, braking action reduction |
| SN | Snow | Precipitation | Runway contamination, de-icing required |
| SG | Snow Grains | Precipitation | Very small white opaque grains of ice |
| IC | Ice Crystals (Diamond Dust) | Precipitation | Unfrozen ice needles suspended in sub-zero air |
| PL | Ice Pellets (Sleet) | Precipitation | Bouncing transparent ice beads; severe icing aloft |
| GR | Hail (>5 mm) | Precipitation | Structural aircraft damage, severe thunderstorm alert |
| GS | Small Hail / Snow Pellets (<5 mm) | Precipitation | Moderate convective precipitation |
| UP | Unknown Precipitation | Precipitation | Automated sensor (AO2) detected unclassified precip |
| BR | Mist (Visibility 1,000–5,000 m) | Obscuration | Water droplets; relative humidity > 95% |
| FG | Fog (Visibility < 1,000 m) | Obscuration | Low visibility procedures (LVP / CAT II/III) active |
| FU | Smoke | Obscuration | Atmospheric combustion particulates |
| VA | Volcanic Ash | Obscuration | Immediate flight hazard; jet engine flameout risk |
| DU | Widespread Dust | Obscuration | Suspended fine soil particles |
| SA | Sand | Obscuration | Ingestion hazard; surface abrasive |
| HZ | Haze | Obscuration | Fine dry dust/pollution particles; humidity < 80% |
| PY | Spray | Obscuration | Water droplets whipped up by high winds |
| SQ | Squall | Other Weather | Sudden wind speed increase ≥ 16 kt sustained ≥ 22 kt |
| FC | Funnel Cloud / Tornado / Waterspout | Other Weather | Severe vortex; immediate aerodrome closure |
| SS | Sandstorm | Other Weather | Sand whipped up by wind reducing visibility |
| DS | Duststorm | Other Weather | Dust wall reducing surface visibility |
| TS | Thunderstorm | Descriptor | Convective storm; lightning, hail, severe turbulence |
| SH | Showers | Descriptor | Sudden start/stop precipitation from cumuliform clouds |
| FZ | Freezing (Supercooled) | Descriptor | Freezing rain/drizzle/fog forming clear ice on impact |
| BL | Blowing (>2 m above ground) | Descriptor | Wind-lifted snow/sand/dust above eye level |
| DR | Low Drifting (<2 m above ground) | Descriptor | Wind-lifted snow/sand below eye level |
| MI | Shallow | Descriptor | Ground-based fog layer < 2 m thick |
| BC | Patches | Descriptor | Fog patches covering part of aerodrome |
| PR | Partial | Descriptor | Substantial part of aerodrome covered by fog |
Cloud Coverage (Oktas), Ceiling & Trend Indicators
| Code | Coverage (Oktas / Eighths) | Operational Flight Status |
|---|---|---|
| SKC / CLR | 0 oktas (Sky Clear) | Unrestricted visual flight conditions |
| FEW | 1 to 2 oktas (1/8 to 2/8 sky covered) | Scattered fair weather |
| SCT | 3 to 4 oktas (3/8 to 4/8 sky covered) | Scattered clouds; no official ceiling |
| BKN | 5 to 7 oktas (5/8 to 7/8 sky covered) | Constitutes an official Ceiling |
| OVC | 8 oktas (8/8 complete overcast) | Constitutes an official Ceiling |
| VV | Vertical Visibility (Surface Obscuration) | Fog/snow obscured vertical limit |
| CB | Cumulonimbus Cloud | Thunderstorm cloud; severe hazard |
| TCU | Towering Cumulus | Developing thunderstorm cell |
| NOSIG | No Significant Change | Trend forecast: stable conditions for next 2 hours |
| BECMG | Becoming | Gradual transition to new weather conditions |
| TEMPO | Temporary | Fluctuations lasting < 1 hour and < half the period |