METAR Weather Report

Private Pilot License (PPL) Notes

This section introduces the Aviation Routine Weather Report (METAR), a critical weather observation product for pilots, detailing how to read and interpret METARs for safe flight operations.

Understanding METARs:

1. Definition of METAR:
   1. An Aviation Routine Weather Report providing observational weather conditions at an airport.
2. Components measured:
   1. Wind speed and direction
   2. Surface visibility
   3. Precipitation
   4. Cloud coverage and height
   5. Air temperature and dew point
   6. Altimeter setting
3. Standardized coding:
   1. Used by all airports in the U.S.
   2. Allows pilots to determine current conditions at a glance.

Reading METARs:

1. Update frequency:
   1. Updated hourly, typically 5-10 minutes before the top of the hour.
   2. SPECI reports issued if conditions change significantly before the next update.
2. Sequence of information:
   1. Where: Airport identifier
   2. When: Date and time of observation
   3. Wind: Direction and speed
   4. Visibility
   5. Weather phenomena (precipitation, obscurations)
   6. Sky conditions (cloud coverage and height)
   7. Temperature and dew point
   8. Altimeter setting
   9. Remarks
3. Learning to decode:
   1. Important to learn how to decode METARs manually.
   2. Many apps and websites provide decoded versions for assistance.

METAR Elements Explained:

1. Location (Airport identifier):
   1. Example: KRSW for Fort Myers, Florida.
   2. 'K' prefix used for airports in the contiguous 48 states.
2. Date and time:
   1. First two digits: Day of the month.
   2. Next four digits: Time in Coordinated Universal Time (UTC).
   3. Example: 241953Z indicates the observation was taken on the 24th at 1953 UTC.
3. Wind:
   1. Direction from which the wind is blowing, in degrees true.
   2. Speed in knots.
   3. Gusts indicated by 'G' followed by gust speed.
   4. Example: 12015G20KT means wind from 120 degrees at 15 knots gusting to 20 knots.
4. Visibility:
   1. Reported in statute miles (SM) in the U.S.
   2. Example: 5SM indicates visibility of 5 statute miles.
5. Weather phenomena:
   1. Precipitation types indicated by codes.
   2. Intensity modifiers: '-' for light, '+' for heavy.
   3. Example: -RA indicates light rain.
   4. Obscurations like mist (BR), fog (FG).
   5. 'BR' indicates mist; for visibility 5/8 mile or greater.
6. Sky conditions:
   1. Cloud coverage coded by amount:
      1. SKC: Sky Clear (0 oktas)
      2. FEW: Few (1-2 oktas)
      3. SCT: Scattered (3-4 oktas)
      4. BKN: Broken (5-7 oktas)
      5. OVC: Overcast (8 oktas)
   2. Cloud heights reported in hundreds of feet AGL.
   3. Ceiling defined as the lowest broken or overcast layer.
   4. Example: SCT048 BKN065 OVC075 indicates scattered clouds at 4,800 ft, broken at 6,500 ft, overcast at 7,500 ft.
7. Temperature and Dew Point:
   1. Reported in degrees Celsius.
   2. Negative values indicated by 'M' (minus).
   3. Example: 25/19 indicates a temperature of 25°C and dew point of 19°C.
8. Altimeter Setting:
   1. Prefixed by 'A', given in inches of mercury.
   2. Example: A3017 indicates an altimeter setting of 30.17 inches of mercury.
9. Remarks:
   1. Additional information about the observation.
   2. Examples:
      1. Peak wind: PK WND 10030/1929 (Peak wind from 100° at 30 knots at 1929Z)
      2. Wind shift: WSHFT 1927 (Wind shift occurred at 1927Z)
   3. Sea level pressure, precise temperature/dew point, etc.

Additional Notes on METARs:

1. Runway Visual Range (RVR):
   1. Visibility for a specific runway, reported in feet.
   2. Important for instrument operations.
2. Airport Identifiers outside the contiguous U.S.:
   1. Differing prefixes, e.g., 'M' for Mexico (MMMX for Mexico City), 'C' for Canada (CYYZ for Toronto).
3. Modifiers:
   1. 'COR' indicates a corrected observation.
   2. 'AUTO' denotes automated reports from AWOS/ASOS stations.
   3. 'AO1' and 'AO2' indicate types of sensors used.
      1. 'AO1' cannot distinguish between types of precipitation.
      2. 'AO2' can discriminate between precipitation types.
4. Wind Reporting:
   1. Calm winds indicated by '00000KT' (five zeros).
   2. Variable winds:
      1. 'VRB' used when wind direction is variable at less than 6 knots.
      2. With wind direction variable between two directions: e.g., 180V210 indicates wind varying between 180° and 210°.
5. Precipitation Intensity:
   1. '+' indicates heavy precipitation.
   2. '-' indicates light precipitation.
   3. No sign indicates moderate intensity.
6. Missing Data:
   1. Omitted from the report if unavailable.
   2. Knowing the sequence helps identify missing elements.
   3. Dew point missing example: If only temperature is given without '/'.
7. Remarks Section:
   1. May include additional weather phenomena timing.
   2. Example: Thunderstorm beginning and ending times.
8. Further Learning:
   1. Aviation Weather Handbook provides detailed information.
   2. Includes decoding charts for weather phenomena codes.

Accessing METARs:

1. Aviation Weather Center (aviationweather.gov):
   1. Interactive maps showing METAR data graphically.
   2. Option to view raw and decoded METARs.
   3. Access specific airport METARs via 'METAR Data' under 'Products'.
2. Aviation Apps:
   1. Example: ForeFlight app.
   2. Access METARs on the 'Airports' page under the 'Weather' tab.
   3. Interactive maps display flight categories and METARs.

Conclusion:

1. METARs are essential for pre-flight planning:
   1. Provide current weather conditions at airports.
   2. Important for making go/no-go decisions.
2. Practice reading METARs:
   1. Review METARs daily to become proficient.
   2. Use alongside other weather products for comprehensive briefings.

By learning to read and interpret METARs, you enhance your situational awareness and contribute to safer flight operations.