Information for flight planning

Aerodrome Meteorological Reports (METAR and SPECI)

METAR (Meteorological Aerodrome Report)

It is a routine report of meteorological conditions observed at an aerodrome. It is generally issued every 30 or 60 minutes.

SPECI (Special Report)

It is a special report issued when significant changes (deterioration or improvement) occur in meteorological conditions between routine reports (e.g., change in wind, visibility, low clouds, or onset/cessation of thunderstorms).

Basic Decoding

Example: EGKK 191050Z 09002KT 0200 R08R/0350 VV001 M03/M02 Q1008

• Identifier: EGKK (Gatwick).
• Date/Time: 191050Z (Day 19 at 10:50 UTC).
• Wind: 09002KT (090 degrees, 2 knots).
• Visibility: 0200 (200 metres).
• RVR: R08R/0350 (Runway 08 Right, 350 metres).
  • Trends: U (Increasing), D (Decreasing), N (No change).
  • Prefixes: P (More than, e.g., P1500), M (Less than, e.g., M0050).
• Clouds/Vertical Visibility: VV001 (Vertical visibility 100 feet - sky obscured).
  • FEW, SCT, BKN, OVC.
  • NSC: No Significant Clouds (no clouds of operational significance, but not CAVOK).
  • CAVOK: Visibility $\ge$ 10 km, no clouds below 5000 ft or MSA, no significant phenomena (CB/TCU).
• Temperature/Dew Point: M03/M02 (-3°C / -2°C).
• QNH: Q1008 (1008 hPa).

Trend Forecast

Added at the end of the METAR and is valid for 2 hours.

• NOSIG: No significant changes forecast.
• BECMG: Gradual or regular change to new conditions.
• TEMPO: Temporary fluctuations (less than 1 hour each time, and less than half the total period).

Aerodrome Forecasts (TAF)

The TAF (Terminal Aerodrome Forecast) describes the expected meteorological conditions at an aerodrome during a specific period (usually 9, 24, or 30 hours).

Change Indicators

• BECMG (Becoming): Permanent change expected within the indicated time period.
• TEMPO (Temporary): Temporary conditions lasting less than one hour.
• PROB30 / PROB40: 30% or 40% probability of a phenomenon occurring (usually used with TEMPO).

En-route Information (SIGMET and AIRMET)

SIGMET

Information concerning en-route weather phenomena which may affect the safety of all aircraft.

• Validity: Maximum 4 hours (6 hours for Volcanic Ash and Tropical Cyclones).
• Phenomena:
  • Thunderstorms (TS) (Obscured, Embedded, Frequent, Squall line).
  • Severe Turbulence (SEV TURB).
  • Severe Icing (SEV ICE).
  • Severe Mountain Waves (SEV MTW).
  • Heavy dust/sand storms.
  • Volcanic Ash (VA).
  • Tropical Cyclone (TC).

AIRMET

Similar to SIGMET but for phenomena affecting the safety of low-level flights (generally below FL100 or FL150 in mountainous areas) and which were not included in the area forecast.

Warnings and Alerts

Aerodrome Warnings

Concise information on conditions that could adversely affect aircraft on the ground (including parked aircraft) and facilities.

• Examples: Strong wind, hail, snow, frost, ground icing.

Wind Shear Alert

Warnings about the observed or expected existence of wind shear in the approach or take-off path (between runway level and 500 m / 1600 ft).

Volcanic Ash and Cyclone Advisories

Issued by VAAC (Volcanic Ash Advisory Centres) and TCAC (Tropical Cyclone Advisory Centres) to guide meteorological watch offices in issuing SIGMETs.

Flight Information Services

ATIS (Automatic Terminal Information Service)

Continuous broadcast (voice or D-ATIS data link) of routine information for arriving or departing aircraft. Contains operational (runway in use) and meteorological (wind, visibility, clouds, temp, QNH) information.

VOLMET

Broadcast of meteorological information (METAR, SPECI, TAF, SIGMET) for aircraft in flight.

Aircraft Reports (AIREP)

• Routine AIREP: Position and basic meteorological information.
• Special AIREP (ARS): Must be issued when hazardous unforecast or significant conditions are encountered, such as:
  • Moderate or severe turbulence.
  • Moderate or severe icing.
  • Severe mountain waves.
  • Thunderstorms with or without hail.
  • Volcanic ash cloud.