METAR

METAR

The word METAR comes from the French phrase "message d’observation météorologique régulière pour l’aviation". It is thought to be a contraction of the French words MÉTéorologique ("Weather") Aviation Régulière ("Routine"). A METAR is a codified observation message indicating airfield weather conditions observed at a given time. Such a message is established every hour, even sometimes every 30 minutes or shorter due to fast and heavy weather changes which affects the traffic flow.

Sample:

LOWW 011220Z 33007KT 280V020 3000 R34/1500 +RASH FEW040 BKN058TCU 16/07 Q1014 RETS WS RWY34
34231091 BECMG -SHRA SCT030CB

Detailed explanation

1.) Location Identifier: LOWW
The four-letter ICAO code of the observing location.

2.) Day of Month/Zulu Time: 011220Z

3.) Wind: 33007KT
Wind direction (true heading), rounded to the nearest ten degrees and always expressed as three digits. Direction can be given as VRB if wind direction is variable and wind speed is at most 3 knots.
plus
average wind speed of last 10 minutes in knots.
or
maximum gust wind speed in knots.
If it is calm, the wind is given as 00000KT.

4.) Variable Wind Direction: 280V020
This field is used if the total variation of wind direction during the last 10 minutes is 60 degrees or more and wind speed is more than 3 knots. The direction extrema are given in clockwise order

5.) Horizontal Visibility: 3000
Usually, only the minimum visibility is reported. If the minimum is less than 1500m and the maximum is over 5000m, the maximum visibility and its direction are indicated by a second visibility group following the minimum visibility.

6.) RVR Runway Visual Range: R34/1500
Runway designator and runway visibility in meters.

7.) Significant Weather: +RASH
Intensity is expressed by: + = heavy, - = light, nothing = moderate
Proximity is described by: VC = ViCinity (within 8km)

  BC = Banc - fog bench
  BL = Blowing
  DR = Drifting
  FZ = Freezing
  MI = Mince - thin fog layer
  SH = Shower
  TS = Thunderstorm
  DZ = Drizzle
  GR = Grêle - hail (diameter > 5mm)
  GS = Grêsil - hail (diameter < 5mm)
  IC = Ice Crystal
  PE = Ice Pellets
  RA = Rain
  SG = Snow Grains
  SN = Snow
  BR = Brume - mist (vis 1000 to 3000m)
  DU = Dust
  FG = Fog (vis < 1000m)
  FU = Fumée - smoke (vis < 3000m)
  HZ = Haze
  SA = Sand
  VA = Vulcanic Ashes
  DS = Dust Storm
  FC = Funnel Clouds
  PO = Dust Spins
  SQ = Squall
  SS = Sand Storm

8.) Clouds and Ceiling: FEW040 BKN058TCU

Cloud coverage:

  FEW = few - 1 to 2 octas
  SCT = scattered - 3 to 4 octas
  BKN = broken - 5 to 7 octas
  OVC = overcast - 8 octas

Cloud types:

  CB = cumulunimbus
  TCU = towering cumuli or cumulus congestus

Also common:

  SKC = Sky Clear (no clouds)
  OVC/// = clouds covering the sky and which base is below aerodrome level
  VV/// = sky not visible
  VV002 = vertical visibility is 200ft
  CAVOK = ceiling and visibility is OK (vis > 10km and SKC)

9.) Temperature and Dew Point: 16/07
The difference between temperature and dew pont is called "spread", the smaller the spread the higher the risk of precipitation.

10.) Pressure, QNH (altimeter setting): Q1014
QNH = 1014 hPa (hectopascals - 1hPa = 1mb - millibar)

11.) Recent Weather: RETS
Recent Thunderstorm
Also:

  RERA = recent rain
  RESN = recent snow
  NOSIG = no significant change

12.) Wind Shear: WS RWY34
Also:

  WS TKOF RWY 16 = windshear when taking of runway 16
  WS LDG RWY 34 = windshear when landing at runway 34
  WS ALL RWYS = windshear all runways

13.) Runway Status: 34231091
34 = runway 34
2 = wet
3 = covering 26 to 50% of runway surface
10 = 10mm thick
91 = braking action poor

Explaination:
1st and 2nd figure = runway designator
3rd figure = type of deposit on the runway

  0 = runway clean and dry
  1 = damp
  2 = wet
  3 = frost
  4 = snow
  5 = wet snow
  6 = slush
  7 = ice
  8 = compacted snow
  9 = snow drift
  / = unknown, removal in progress

4th figure = percentage of runway contamination

  1 = less than 10%
  2 = 11 to 25%
  3 = 26 to 50%
  4 = 51 to 100%
  / = unknown, removal in progress

5th and 6th figure = deposit thickness

  01 to 90 = millimeters
  92 = 10cm
  93 = 15cm
  94 = 20cm
  95 = 25cm
  96 = 30cm
  97 = 35cm
  98 = 40cm
  99 = unknown
  // = unable to measure

7th and 8th figure = braking action

  01 to 90 = coefficient 0.01 to 0.90
  or
  91 = poor
  92 = medium to poor
  93 = medium
  94 = medium to good
  95 = good
  99 = uncertain
  // = unknown

14.) Trend: BECMG -SHRA SCT030CB
Consists of following keywords and other METAR components:

  BECMG: becoming
  TEMPO: temporarily
  NOSIG: no significant change expected within 2 hours
  AT: at
  FM: from
  TL: until

15.) Remarks:
RMK followed by METAR components and miscellaneous abbreviations.

Links

• TAF