GROUP How to Decode METAR reports

Aviation Routine Weather Report (METAR)​

A METAR is a codified observation message indicating an airfield weather conditions observed at a given time. Such a message is established every hour.

Decoding METAR (Meteorological Aerodrome Report) reports is a straightforward process once you understand the standard format and abbreviations. METARs provide a snapshot of weather conditions at an airport, typically updated hourly, and are widely used in aviation, including in simulators like DCS for realistic mission planning. Below, I’ll break down the components step-by-step and show you how to decode a sample report.

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METAR Structure​

A METAR report follows a consistent sequence of elements, though some parts are optional depending on conditions. Here’s the typical order:

1. Station Identifier (ICAO code)
2. Date/Time (in UTC/Zulu time)
3. Modifier (e.g., AUTO, COR) [Optional]
4. Wind (direction and speed)
5. Visibility (in meters or statute miles)
6. Runway Visual Range (RVR) [Optional]
7. Weather Phenomena (e.g., rain, snow)
8. Sky Condition (cloud coverage and height)
9. Temperature/Dewpoint (in Celsius)
10. Altimeter Setting (pressure in hPa or inHg)
11. Remarks (RMK) [Optional]

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Step-by-Step Decoding​

Let’s decode a METAR as an example:
KJFK 221551Z 31015G25KT 10SM -RA BKN030 OVC070 04/02 A2992 RMK AO2 SLP132

1. Station Identifier​

• KJFK: The ICAO code for John F. Kennedy International Airport (New York).
  • "K" indicates a U.S. airport, followed by a 3-letter identifier.

2. Date/Time​

• 221551Z: 22nd day of the month, 15:51 UTC (Zulu time).
  • First two digits = day, next four = HHMM in 24-hour UTC.

3. Modifier [Optional]​

• None here, but you might see:
  • AUTO: Automated report (no human observer).
  • COR: Corrected report.

4. Wind​

• 31015G25KT: Wind from 310° (northwest) at 15 knots, gusting to 25 knots.
  • First three digits = direction (true north, rounded to nearest 10°).
  • Next two digits = speed. "G" = gusts, followed by peak gust speed.
  • KT = knots (could be "MPS" for meters per second or "KMH" for kilometers per hour).

5. Visibility​

• 10SM: 10 statute miles.
  • In the U.S., visibility is in statute miles (SM). Elsewhere, it’s often in meters (e.g., 8000 = 8,000 meters).
  • If below 5,000 meters, it’s precise (e.g., 0800 = 800 meters).

6. Runway Visual Range (RVR) [Optional]​

• Not present here, but might look like: R36/4000FT (Runway 36, 4,000 feet visibility).

7. Weather Phenomena​

• -RA: Light rain.
  • Prefix: "-" = light, no prefix = moderate, "+" = heavy.
  • Codes:
    • RA = Rain
    • SN = Snow
    • TS = Thunderstorm
    • SH = Showers
    • DZ = Drizzle
    • FG = Fog
    • Multiple can appear (e.g., +TSRA = heavy thunderstorm with rain).

8. Sky Condition​

• BKN030 OVC070: Broken clouds at 3,000 feet above ground level (AGL), overcast at 7,000 feet AGL.
  • Coverage:
    • SKC = Sky clear
    • FEW = Few (1/8–2/8)
    • SCT = Scattered (3/8–4/8)
    • BKN = Broken (5/8–7/8)
    • OVC = Overcast (8/8)
  • Height: Three digits in hundreds of feet AGL (030 = 3,000 ft).
  • Note: In DCS or some regions, height might be above aerodrome level; check local charts.

9. Temperature/Dewpoint​

• 04/02: Temperature 4°C, dewpoint 2°C.
  • Two digits each, separated by "/".
  • If negative, prefixed with "M" (e.g., M02 = -2°C).
  • Close temp/dewpoint (e.g., 4/2) suggests high humidity and potential fog.

10. Altimeter Setting​

• A2992: Altimeter setting 29.92 inHg (standard pressure).
  • "A" = inches of mercury (U.S.); elsewhere, might be "Q" for hPa (e.g., Q1013 = 1013 hPa).
  • Four digits = pressure value (2992 = 29.92 inHg).

11. Remarks (RMK) [Optional]​

• RMK AO2 SLP132:
  • AO2: Automated station with precipitation discriminator.
  • SLP132: Sea-level pressure 1013.2 hPa (SLP = sea-level pressure, 132 = 013.2, with "10" assumed).

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Decoded Example​

KJFK 221551Z 31015G25KT 10SM -RA BKN030 OVC070 04/02 A2992 RMK AO2 SLP132

• Location: JFK Airport, New York.
• Time: 22nd, 15:51 UTC.
• Wind: 310° (NW) at 15 knots, gusting to 25 knots.
• Visibility: 10 statute miles.
• Weather: Light rain.
• Clouds: Broken at 3,000 ft AGL, overcast at 7,000 ft AGL.
• Temp/Dewpoint: 4°C / 2°C.
• Pressure: 29.92 inHg, sea-level pressure 1013.2 hPa.
• Notes: Automated station with precip sensor.

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Tips for DCS Use​

• Wind: Adjust takeoff/landing runway based on direction (e.g., 310° favors Runway 31).
• Visibility/Weather: Impacts targeting (e.g., IR Mavericks struggle in heavy rain).
• Clouds: Affects laser-guided weapons (e.g., GBU-12 needs clear LOS).
• Pressure: Set your altimeter in the cockpit to match (29.92 inHg here).

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Practice METAR​

Try decoding this: EGLL 221230Z 23010KT 5000 RA OVC008 12/11 Q1010

• Answer: London Heathrow, 22nd 12:30 UTC, wind 230° at 10 knots, 5,000m visibility, moderate rain, overcast at 800 ft AGL, 12°C/11°C, 1010 hPa.

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METAR /TAF Abbreviations / Cloud Types​