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METAR : Meteorological Terminal Air Report

Definition

Meteorological Terminal Air Report (METAR) – literally ‘Meteorological Terminal Air Report’ or more straightforwardly ‘Routine aerodrome meteorological report’

Code Name

The indicator group e.g. METAR, SPECI, or TREND as appropriate. Where a number of METARs are issued in the same bulletin, this, along with a date time group may be in the bulletin header.

Location

The ICAO indicator of the reporting station eg. EGLL.

Date/Time of Report

The day of the month and the time of the observation in hours and minutes UTC e.g. 191350Z.

AUTO

The optional code word AUTO indicates that the report has been generated using data from an automated observing system.

Surface Wind

The mean wind direction in degrees true to the nearest 10 degrees, from which the wind is blowing and the mean wind speed in knots over the 10 minute period immediately preceding the observation e.g. 35015KT = 350 degrees true/15 kts; VRB05KT = variable/5 kts; 00000 = CALM. If gusts exceed the mean wind speed by 10kts or more in the 10 minutes preceding the time of the report, a letter G and 2 more figures are added to indicate the maximum wind speed e.g. 23018G30KT = 230 degrees true/18 kts gusting to a maximum of 30 kts. Reports may express wind speed in metres per second (‘MPS) or Kilometres per hour (KPH). Winds greater than 100 kts or more shall be preceded by the letter P and reported as P99KT or P99MPS or P199KPH.

Visibility

Reported in a four figure group (e.g. 0400 = 400 metres; 8000 = 8 km) up to but excluding 10 km; 9999 = 10km or more; 0000 = less than 50 metres visibility.

Runway Visual Range (RVR)

  • Aerodromes may include a letter indicator R followed by the runway designator, a”/” and the touchdown zone RVR in metres, e.g. R06/0400. If the RVR is assessed on 2 or more runways simultaneously then the RVR group will be repeated.
  • Parallel runways will have LC, or R added to the runway designator e.g. R24L/1100.
  • If the RVR is greater than the maximum value that can be measured, P will precede this value e.g. R24L/P1500.
  • If the RVR is less than the minimum value that can be measured , M will precede this value e.g. R24L/M0050.
  • If RVR trends can be measured then UD, or N will follow the RVR value to indicate increasing, decreasing or no change respectively.

Weather

Weather is indicated by up to 3 groups comprising symbols and letters from the following:

 = slight + = Heavy BC = Patches BL = Blowing
BR = Mist DR = Low Drifting DS = Dust Storm DU = Widespread Dust
DZ = Drizzle FG = Fog FC = Funnel Cloud (e.g. Tornado) FU = Smoke
FZ = Freezing GR = Hail GS = Small Hail HZ = Haze
IC = Ice Crystals MI = Shallow PL = Ice Pellets PO = Dust Devils
RA = Rain SA = Sand SG = Snow Grains SH = Shower
SN = Snow SQ = Squall SS = Sandstorm TS = Thunderstorm
VA = Volcanic Ash VC = In the vicinity (nearby) UP = Unidentified Precipitation RE = Recent

e.g – FZDZ = Slight Freezing Drizzle; + SHRASN = Heavy Shower of Rain and Snow; REUP = Recent Unidentified Precipitation.

Cloud

Cloud amount is reported as FEW = few (1-2 oktas), SCT = scattered (3-4 oktas), BKN = broken (5-7 oktas) or OVC = overcast (8 oktas), followed by the height of the cloud base in hundreds of feet above aerodrome elevation e.g. SCT018 = scattered clouds at 1800 ft. Note that in area and route forecasts, heights are AMSL or standard pressure altitudes.

Selection of cloud layers reported is made as follows:

  • The lowest Layer;
  • The next lowest layer of SCT or more;
  • The next higher layer of BKN or more;
  • Significant convective cloud (CB or TCU) if not already reported.

Sky obscured is given as VV followed by the vertical visibility in hundreds of feet. When the vertical visibility has not been measured, the group will be VV///.

When there are no clouds of operational significance to report, no CB or TCU and CAVOK is not appropriate, the abbreviation NSC (No Significant Cloud) is used.

CAVOK

The Visibility, Cloud, and Weather groups are replaced by the term CAVOK (cloud and visibility OK) when the following conditions exist simultaneously:

  • Visibility is 10km or more.
  • No CB or TCU and no cloud below 5000 feet or Minimum Sector Altitude (MSA) (whichever is the greater).
  • No significant weather at or in the vicinity of the aerodrome.

Temperature

Air temperature and dewpoint are reported in whole degrees Celsius, e.g. 10/07 = Temperature 10°C/ Dew point 7°C.

QNH

QNH is stated to the nearest whole hectopascal (equivalent to a millibar) rounded down and preceded by the letter Q e.g. Q1013 = QNH 1013 Hectopascals.

Recent Weather

Significant recent weather observed in the period since the last routine observation will be reported by using the code letters for weather preceded by the letters RE e.g. RETS = Recent Thunderstorm.

Wind Shear

In a METAR, civil aerodromes may include wind shear if reported along the take off or approach paths in the lowest 1600 ft with reference to the runway. WS is used to begin the group, e.g. WS TKOF RWY20. If the wind shear is affecting all runways, WS ALL RWY is reported.

Aerodrome Colour State

UK military and USAFE aerodromes will include the abbreviated colour state at the end of the message and ad the forecast colour state after the TREND.

Runway State Group (RSG)

An 8-figure group which may be added to METAR from civil aerodromes.

  • Runway designator (first two digits)

27 = Rwy 27 or 27L

77 = Rwy 27R (50 added to the designator for “right” runway)

88 = All runways

99 = repetition of the last message as no new information received.

  • Runway Deposits (third digit)

0 = Clear and dry

1 = Damp

2 = Wet or water patches

3 = Rime or frost covered (depth normally less than 1mm)

4 = Dry snow

5 = Wet snow

6 = Slush

7 = Ice

8 = compacted or rolled snow

9 = frozen ruts or ridges

/ = type of deposit not reported (e.g. due to rwy clearance in progress)

  • Extent of runway contamination (fourth digit)

1 = 10% or less

2 = 11% to 25%

5 = 26% to 50%

9 = 51% to 100%

/ = not reported (e.g. due to rwy clearance in progress)

  • Depth of Deposit

the quoted depth is the mean of a number of readings or, if operationally significant, the greatest depth measured.

00 = less than 1mm

01 = 1mm etc

to

90 = 90mm

91 = not used

92 = 10cm

93 = 15cm

94 = 20cm

95 = 25cm

96 = 30cm

97 = 35cm

98 = 40cm or more

99 = Rwy(s) non-operational due to snow, slush, ice, large drifts or runway clearance, but depth not reported.

// = depth of deposit operationally not significant or measurable.

  • Friction Coefficient or Braking Action (seventh and eighth digits)

The mean value is transmitted or, if operationally significant, the lowest value, e.g.:

28 = friction coefficient 0.28

38 = friction coefficient 0.38

or

91 = Braking action: Poor

92 = Braking action: Medium/Poor

93 = Braking action: Medium

94 = Braking action: Medium/Good

95 = Braking action: Good

99 = Figures unreliable (e.g. if equipment has been used which does not measure satisfactorily in slush or snow.)

// = Braking action not reported (e.g. runway not operational; aerodrome closed; etc.)

Note: If contamination conditions cease to exist, the abbreviation CLRD is used, e.g.

24CLRD93 = Rwy 24 cleared; Braking action: Medium/Good

88CLRD95 = All rwys cleared; Braking Action: Good

TREND

TREND forecasts are indicated by BECMG (Becoming) or TEMPO (temporary) which may be followed by a time group (hours and minutes UTC) preceded by one of the letter indicated FM (from), TL(until), AT (at)

e.g. BECMG FM1030 TL1130

NOSIG replaces the TREND group when no significant changes are forecast to occur during the 2 hour forecast period.

To indicate the end of significant weather the abbreviation NSW (No Significant Weather) is used.

Only those elements for which a significant change is expected should be included in a TREND.


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