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.
LOWW 011220Z 33007KT 280V020 3000 R34/1500 +RASH FEW040 BKN058TCU 16/07 Q1014 RETS WS RWY34 34231091 BECMG -SHRA SCT030CB
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.
average wind speed of last 10 minutes in knots.
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
FEW = few - 1 to 2 octas SCT = scattered - 3 to 4 octas BKN = broken - 5 to 7 octas OVC = overcast - 8 octas
CB = cumulunimbus TCU = towering cumuli or cumulus congestus
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
RERA = recent rain RESN = recent snow NOSIG = no significant change
12.) Wind Shear: WS RWY34
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
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
RMK followed by METAR components and miscellaneous abbreviations.