The METAR Code for Surface Observations

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The METAR Code for Surface Observations
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Office of the Federal Coordinator for Meteorology

• Mission To ensure the effective use of federal
  meteorological resources by leading the
  systematic coordination of operational weather
  requirements and services, and supporting
  research, among the federal agencies.
• http//www.ofcm.gov

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Federal Meteorological Handbook No. 1

• Federal Meteorological Handbook No.1 describes
  the surface weather observing program of the U.S.
  National Weather Service.
• http//www.ofcm.gov/fmh-1/fmh1.html

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• On July 1, 1996 the National Weather Service
  changed from the SAO (Surface Airways
  Observations) to the METAR/SPECI code for
  reporting hourly observations of surface weather
  data.

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• The METAR Code is discussed in Chapter 12 of
  FMH-1.

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• METAR , message dobservation météorologique
  régulière pour laviation, which is the French
  expression for Aviation Routine Meteorological
  Report.
• SPECI is derived from the French expression for
  Aviation Selected Special Meteorological Report.

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The METAR Code

• METAR or SPECI CCCC YYGGggZ AUTO or COR
  dddff(f)Gfmfm(fm)KT dndndnVdxdxdx VVVVVSM
  RDRDR/VRVRVRVR or RDRDRVNVNVNVNVVXVXVXVXFT ww
  NsNsNshshshs or VVhshshs or SKC/CLR TT/TdTd
  APHPHPHPH RMK (Automated, Plain Language)
  (Additive Data and Automated Maintenance
  Indicators)

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Type of Report

• METAR or SPECI CCCC YYGGggZ
• METAR or SPECI is the type of report.
• METAR is the routine hourly surface report
• SPECI is a special report based on the criteria
  in Chapter 2 of FMH-1.

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Station ID

• METAR or SPECI CCCC YYGGggZ
• CCCC is the station identification code.
• For example KCMH is the code for Port Columbus
  International airport.

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Day and Time

• METAR or SPECI CCCC YYGGggZ
• YYGGggZ is the day and time of the report.
• YY is the day of the month.
• GGgg is the time of the report in UTC (Universal
  Coordinated Time)

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Universal Coordinated Time

• UTC EDT 4 hours
• UTC EST 5 hours.
• For example,
• 1945 UTC 1545 EDT 345 p.m. EDT

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• If YYGGggZ is 241848Z,
• then it indicates the 24th day of the month,
• and the time of the report was 1848 UTC or
• 248 p.m. EDT.

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• AUTO or COR
• AUTO indicates a fully automated observation with
  no human intervention or oversight.
• COR indicates a report issued to correct an error
  in a METAR or SPECI report.

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Wind Speed and Direction

• dddff(f)Gfmfm(fm)KT is the block of data that
  specifies the wind direction, wind speed and
  speed of the wind gusts.
• ddd is the compass direction of the wind rounded
  to the nearest tens of degrees.
• ff(f) is a two or three digit number that gives
  the wind speed in knots.

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• Gfmfm(fm) is coded when there is a variation of
  more than 10 knots during the most recent 10
  minutes.
• fmfm(fm) is a two or three digit number that
  gives the speed of the wind gusts in knots.

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Examples

• 27005KT indicates a wind that is blowing from 270
  degrees (i.e. from the west) at a speed of 5
  knots
• 16018G35KT indicates a wind that is blowing from
  160 degrees (i.e. from the south-southeast) at a
  speed of 18 knots with gusts to 35 knots.

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Examples (cont.)

• 120105G120KT indicates a wind that is blowing
  from 120 degrees (i.e. from the east-southeast at
  a speed of 105 knots with gusts to 120 knots.
• A report of a calm wind is reported as
• 00000KT

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Variable Wind Directions

• The wind direction may be considered variable if
  during the two-minute evaluation period
• the wind speed is less than 6 knots or
• the wind direction varies by 60 degrees or more
  when the average wind speed it greater than 6
  knots.

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Variable Wind Directions (cont.)

• VRB may be coded in the ddd location if the wind
  speed is less than 6 knots.
• For example
• VRB03KT indicates variable winds at 3 knots.

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Variable Wind Directions

• When the wind direction is variable and the wind
  speed is more than 6 knots, it is coded as
• dndndnVdxdxdx

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Variable Wind Directions (cont.)

• For example, a report of
• 21010KT 180V240 would indicate a wind speed of 10
  knots with the wind direction varying between 180
  and 240 degrees.

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Visibility

• VVVVVSM indicates the visibility in statute
  miles.
• 10SM would indicate a visibility of 10 statue
  miles.
• 2 1/2SM would indicate a visibility of 2.5
  statute miles.

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Visibility (cont.)

• M at the beginning of the visibility group from
  an automated station indicates a visibility less
  than the number reported for VVVVV.
• For example,
• M1/4SM indicates a visibility of less than 0.25
  statute mile.

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Runway Visual Range

• RDRDR/VRVRVRVRFT is the group for the runway
  visual range.
• R indicates runway number follows.
• DRDR indicates the runway number.
• VRVRVRVR indicates the visual range in feet.
• FT indicates that the units are in feet.

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Runway Visual Range

• When the runway visual range is variable it is
  coded as
• RDRDR/VnVnVnVnVVxVxVxVxFT
• R indicates runway number follows.
• DRDR indicates the runway number.
• VnVnVnVn indicates the lowest runway visual range
  in feet.
• V indicates variable.

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• VxVXVXVx indicates the greatest runway visual
  range in feet.
• FT indicates the units are feet.

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Present Weather

• ww is the position of the present weather
  group.
• Present weather includes precipitation,
  obscurations, well-developed dust/sand whirls,
  squalls, tornadic activity, sandstorms and
  duststorms.

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Intensity or Proximity

• - Light (up to 0.10 inch per hour)
• Moderate (0.11 to 0.30 inch per hour)
• Heavy (more than 0.30 inch per hour)
• VC In the vicinity

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Descriptor

• MI Shallow
• PR Partial
• BC Patches
• DR Low Drifting
• BL Blowing
• SH Shower(s)
• TS Thunderstorm
• FZ Freezing

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Precipitation

• DZ Drizzle
• RA Rain
• SN Snow
• SG Snow Grains
• IC Ice Crystals
• PL Ice Pellets (Sleet)
• GR Hail

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Precipitation (cont.)

• GS Small Hail or Snow Pellets
• UP Unknown Precipitation
• The definition of the Present Weather Parameters
  including precipitation types is given in Chapter
  8 of FMH-1.
• http//www.ofcm.gov/fmh-1/pdf/H-CH8.pdf

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Obscuration

• BR Mist
• FG Fog
• FU Smoke
• VA Volcanic Ash
• DU Widespread Dust
• SA Sand
• HZ Haze
• PY Spray

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Other

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

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Present Weather Examples

• -TSRA indicates a thunderstorm with light rain.
• -RA FG indicates light rain and fog.

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Sky Condition Group

• NsNsNshshshs or VVhshshs or SKC/CLR
• NsNsNs indicates the amount of sky covered.
• hshshs indicates the height of the layer coded in
  hundreds of feet above the surface.

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Sky Condition (cont.)

• FEW indicates 1/8 to 2/8 sky coverage.
• SCT indicates 3/8 to 4/8 sky coverage.
• BKN indicates 5/8 to 7/8 sky coverage.
• OVC indicates 8/8 sky coverage.

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Sky Condition (cont.)

• For example,
• SCT060 indicates 3/8 to 4/8 sky (scattered)
  coverage by a layer of clouds at 6000 feet above
  the surface.
• BKN039 OVC100 indicates 5/8 to 7/8 (broken) sky
  coverage at 3900 feet and 8/8 (overcast) sky
  coverage at 10,000 feet.

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Sky Conditions (cont.)

• NsNsNshshshs or VVhshshs or SKC/CLR
• VV indicates the vertical visibility with an
  indefinite ceiling.
• hshshs indicates the vertical visibility into the
  indefinite ceiling in hundreds of feet.

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Sky Conditions (cont.)

• NsNsNshshshs or VVhshshs or SKC/CLR.
• SKC indicates clear conditions at a station where
  the report is augmented by a human observer.
• CLR indicates the Laser Ceilometer detects no
  clouds below 12,000 feet at an automated station.

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Temperature/Dew Point Temperature Group

• TT/TdTd
• TT indicates the temperature rounded to the
  nearest whole degree Celsius.
• TdTd indicates the dew point temperature
  rounded to the nearest whole degree Celsius.

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Temp. and Dew Pt. (cont.)

• Note Temperatures below freezing have a prefix
  M.
• For example,
• 06/M02 indicates a temperature of 6C and a dew
  point temperature of -2C.

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Altimeter Setting

• APHPHPHPH
• A is the international indicator for an altimeter
  setting that is inches of mercury.
• PHPHPHPH is the altimeter setting in hundredths
  of an inch of mercury with the decimal point
  omitted.

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Altimeter Setting (cont.)

• For example,
• A2992 indicates an altimeter setting of 29.92
  inches of mercury.

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International Altimeter Setting

• International Altimeter Setting groups typically
  use a Q to designate that the altimeter setting
  is in units of hectoPascals (hPa). One
  hectoPascal is the same pressure as one millibar.
• The group would look like
• Q where is the altimeter setting in
  hectoPascals.

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International Altimeter Setting (cont.)

• For example,
• Q1013 indicates an altimeter setting of 1013 hPa.

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Practice

• Decode the following METAR report.
• METAR KOSU 252353Z 25024G38KT
• 2 1/2SM RA FEW016 BKN060 BKN080
• 24/19 A3005

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Practice (cont.)

• METAR routine hourly report
• KOSU the OSU airport at Don Scott Field
• 252353Z the 25th day of the month and the time
  of the report was 2353 UTC (753 p.m. EDT)

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Practice (cont.)

• 25024G38KT the wind is blowing from 250 (i.e.
  from the west-southwest) at 24 knots with gusts
  to 38 knots
• 2 1/2SM the visibility is 2.5 statute miles
• RA heavy rain is falling at the time of
  observation

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Practice (cont.)

• FEW016 BKN060 BKN080
• FEW016 1/8 to 2/8 sky coverage at 1600 feet
  above the surface
• BKN060 5/8 to 7/8 sky coverage at 6000 feet
  above the surface
• BKN080 5/8 to 7/8 sky coverage at 8000 feet
  above the surface

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Practice (cont.)

• 24/19 the temperature is 24 and the dew point
  temperature is 19
• A3004 the altimeter setting is 30.04 inches of
  mercury