Here is a review note summarizing the format of the METAR (Meteorological Terminal Aviation Routine Weather Report).

For example, today’s weather at Haneda Airport: METAR RJTT 230900Z 18011KT 9999 VCSH FEW020TCU SCT030 BKN100 24/19 Q1005 NOSIG RMK 1TCU020 4CU030 6AC100 A2970 TCU 10KM N MOV UNKNOWN

Format

1. Report Type Divided into routine METAR reports (METAR) and special weather reports (SPECI). e.g., “METAR”

2. Station Identifier Each station is identified by a four-letter code determined by the International Civil Aviation Organization (ICAO). e.g., “RJTT” represents Haneda Airport.

3. Report Date and Time Represented by 6 digits. The first two digits indicate the date, and the last 4 digits indicate the time of the METAR, given in Coordinated Universal Time (UTC). e.g., “230900Z” represents the 9th hour and 0 minutes on the 23rd. Since Japan’s time zone is UTC+9, this data represents the weather conditions released at 18:00 local time.

4. Wind Direction and Speed The first 3 digits indicate the direction from which the wind is blowing (true azimuth). If the wind direction is variable, it is reported as VRB. The last 2 digits indicate the wind speed in knots; if the speed exceeds 99 knots, it is represented by 3 digits. If there are gusts, the letter G follows the wind speed. If the wind direction varies by more than 60 degrees and the wind speed is greater than 6 knots, a separate set of numbers separated by V will indicate the extremes of the wind direction.

Examples:

• “18011KT” … Wind direction is 180 degrees (i.e., South wind), wind speed is 11 knots, approx. 20 km/h.
• “08003MPS” … Wind direction is 80 degrees, wind speed is 3 meters per second, approx. 10.8 km/h.
• “310P99GP99KT” … Wind speed is gusting over 99 knots, average over 99 knots.
• “00000KT” … Wind speed is below 0.4 knots.
• “VRB03KT” … Wind direction is variable, wind speed is 3 knots.
• “11010KT 070V150” … Average wind direction is 110 degrees, varying between 70 and 150 degrees.
• “03020G40KT” … Wind direction is 30 degrees, average wind speed is 20 knots, instantaneous maximum wind speed is 40 knots.

5. Visibility

• “9999” … 10 km or more
• “0900” … 900 meters
• “0000” … Less than 100 meters
• “CAVOK” No cloud, visibility 10 km or more, no weather phenomena

6. RVR Runway Visual Range (Optional) Marked with R, followed by the Runway number, followed by a slash, then the visual range in meters, and finally an optional trend indicator. The trend is indicated by U (Upward), D (Downward), and N (No change).

• “R34/1400U” … Runway 34 visual range is average 1400 meters and rising.
• “R34/0200D” … Runway 34 visual range is average 200 meters and falling.
• “R34/0400 V 0800 D” … Runway 34 visual range varies from a minimum of 400 meters to a maximum of 800 meters and is falling.
• “R34L/1200N” … Runway 34L visual range is average 1200 meters, trend is unclear/no change.
• “R34R/P1800U” … Runway 34R visual range exceeds the upper observational limit of 1800 meters and is rising.
• “R34/M0200D” … Runway 34 visual range is below the lower observational limit of 200 meters and is falling.

7. Present Weather Includes intensity and proximity, descriptor, precipitation, obstruction to visibility, and other weather phenomena. For example, “+SHSNRAGS” indicates heavy showers and hail (snow pellets); “-DZFG” indicates light drizzle and fog.

7.1 Intensity or Proximity

• “-” … Light
• "" … Moderate (no qualifier)
• “+” … Heavy
• “VC” … Weather information in the vicinity of the airport

7.2 Descriptor

• MI … Shallow (fog)
• BC … Patches (fog)
• PR … Partial (fog)
• DR … Low Drifting (DU, SA, SN blown to height below 2m)
• BL … Blowing (DU, SA, SN blown to height above 2m)
• SH … Showers
• TS … Thunderstorm
• FZ … Freezing

7.3 Precipitation

• DZ … Drizzle
• RA … Rain
• SN … Snow
• SG … Snow Grains
• IC … Ice Crystals
• PL … Ice Pellets
• GR … Hail
• GS … Small Hail and/or Snow Pellets
• UP … Unknown Precipitation

7.4 Obscuration

• BR … Mist (Visibility between 1 and 10 km)
• FG … Fog (Visibility below 1 km)
• FU … Smoke
• VA … Volcanic Ash
• DU … Widespread Dust
• SA … Sand
• HZ … Haze
• PY … Spray

7.5 Other

• PO … Well-Developed Dust/Sand Whirls
• SQ … Squalls
• FC … Funnel Cloud, Tornado, Waterspout
• SS … Sandstorm
• DS … Duststorm

8. Clouds Cloud amount, cloud base height, cloud type.

8.1 Cloud Amount

• FEW … Few (1/8 ~ 2/8)
• SCT … Scattered (3/8 ~ 4/8)
• BKN … Broken (5/8 ~ 7/8)
• OVC … Overcast (8/8)
• NSC … No Significant Cloud
• CAVOK … No cloud, visibility 10 km or more, no weather phenomena

8.2 Cloud Base Height Represented by 3 digits indicating height in hundreds of feet. e.g., 030 indicates 3000 feet.

8.3 Cloud Type TCu and Cb are noted here; other cloud types are noted in RMK.

Low Clouds

• Cu … Cumulus
• Cb … Cumulonimbus
• St … Stratus
• Sc … Stratocumulus
• TCu … Towering Cumulus

Middle Clouds

• Ns … Nimbostratus
• As … Altostratus
• Ac … Altocumulus
• SL … Standing Lenticular Cloud

High Clouds

• Ci … Cirrus
• Cs … Cirrostratus
• Cc … Cirrocumulus

9. Temperature and Dew Point (The temperature at which water vapor in the air condenses into dew is called the dew point.)

• “12/06” … Temperature 12 degrees, dew point 6 degrees.
• “00/M00” … Temperature 0 degrees, dew point minus 0 degrees.
• “M03/M06” … Temperature minus 3 degrees, dew point minus 6 degrees.

10. Altimeter Setting / QNH

• “Q1006” … 1006 Hectopascals
• “A2971” … 29.71 Inches of Mercury
• P/RR … Pressure Rising Rapidly
• P/FR … Pressure Falling Rapidly

11. Trend Forecast

• “NOSIG” … No significant change.
• “RERASN” … Indicated by RE followed by past weather, e.g., Rain (RA) and Snow (SN).

12. Wind Shear

• “WS R16L” … Wind shear occurred on Runway 16L within the last 30 minutes.
• “WS ALL RWY” … Wind shear occurred on all Runways within the last 30 minutes.

13. Remarks RMK Cloud amount, cloud type, cloud base height, pressure, visibility, pilot reports.

• “1TCU020” … 1/8 cloud amount of Towering Cumulus, base height 2000 feet.
• “4CU030” … 4/8 cloud amount of Cumulus, base height 3000 feet.
• “6AC100” … 6/8 cloud amount of Altocumulus, base height 10000 feet.
• “A2970” … 29.70 Inches of Mercury.
• “TCU 10KM N MOV UNKNOWN” … Towering Cumulus located to the North, movement direction unknown.
• “BECMG” … Becoming (regular change)
• “TL0210”, “TIL0210” … Until 02:10.
• “TEMPO” … Temporary
• “HVY TS OHD MOV SE” … Heavy (HVY) Thunderstorm located overhead, moving Southeast.
• “TX33/0307Z” … Maximum temperature 33 degrees, forecast time UTC 03:07 (i.e., 11:07 Beijing time).
• “TN20/22Z” … Minimum temperature 20 degrees, forecast time UTC 22:00 (i.e., 06:00 Beijing time).
• “MOD TURB OBS AT 0044Z VENUS FL210 IN CMB A330” … Moderate turbulence reported, altitude FL210, time UTC 00:44 (i.e., 09:44 Japan time), location at VENUS Waypoint (approx. 50km south of Narita Airport over the sea), reporting aircraft is an Airbus A330 in Climb.
• A01 … Automated Observation w/o Precipitation Discriminator.
• A02 … Automated Observation with Precipitation Discriminator (sometimes seen as AO2).
• AMD … Amended forecast.
• AUTO … Automated observation.
• **B … Beginning.
• CIG … Ceiling.
• FBL … Feeble, Light.
• GRADU … Gradually.
• HVY … Heavy.
• INTER … Intermittent.
• LYR … Layer (e.g., “FU LYR” Smoke layer).
• M** … Minus.
• MOD … Moderate.
• MOV … Moving.
• NSW … No Significant Weather.
• OHD … Overhead.
• PROB … Probability of occurring in %.
• PK … Peak.
• RE** … Recent weather.
• “RI ++” … Rainfall Intensity, ++ indicates greater than 30 mm/hour.
• SD … Snow Depth.
• SEV … Severe.
• SFC … Surface.
• SLP … Sea Level Pressure.
• SQL … Squall Line.
• STNR … Stationary.
• VIRGA … Virga.
• VIS … Visibility.
• VV … Vertical Visibility.
• WND … Wind.
• WTSPT … Waterspout.

Reference Materials 0. Aeronautical Meteorological Codes – JMA Recommended

1. http://www.ofcm.gov/fmh-1/fmh1.htm
2. AIM-JAPAN 2012 Late Edition
   
3. <a href=http://www.wunderground.com/metarFAQ.asp?MR=1>wunderground.com
4. yinlei.org/x-plane10/en/2013/06/noaa.html
5. http://www.omnipot.jp/omnipot/aviation/wxterms.html
6. http://www.fltplan.com/abbreviations.htm Abbreviations Dictionary

End