A METAR (METeorological Airport Report) is an aviation weather observation (not forecast) report. This international code was developed by ICAO members and is approved by the World Meteorological Organization.
This type of message is produced every hour and provides information on weather conditions at an airfield at a given time.

A SPECI is identical to a METAR, except that it is not produced on a regular basis , but on an ad hoc basis. This is a special observation message highlighting a specific meteorological event that has occurred since the last METAR or SPECI was published.

TAF/SHORTTAF: Terminal Airport Forecastis a forecast for an airfield. It is written every three hours. A TAF is valid for 24 or 30 hours (forecast updated every 6 hours), while a SHORTTAF is valid for 9 hours.

A METAR looks like this:
LFPO 041300Z 36020KT 320V040 1200 R26/0400 +RASH BKN040TCU 17/15 Q1015 RETS M2 26791299

It sounds complex, but each element block corresponds to an easy-to-understand element such as wind speed, date, etc.

Structure :

Syntax :

METAR AUTO:
Certain aerodromes equipped with a weather station can, thanks to various sensors, produce and broadcast weather observation messages without human intervention. These automatic observation messages are broadcast under the name METAR AUTO. Identical information measured automatically and identical to that in a METAR

classic: wind, air temperature, dew point, QNH, RVR is calculated from on-site sensors…
Let’s take this example, which is very complicated because it includes all the options that an airport could report:LFPO 041300Z 36020KT 320V040 1200 R26/0400 +RASH BKN040TCU 17/15 Q1015 RETS M2 26791299In the simple version, here, Orly airport indicates that the aircraft landing on runway 26 will have to face a “wind” “varying” from “20 knots” “blowing from true North” with “visibility at 1200m” etc…

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AIRPORT ICAO CODE: CCCC (AUTO)

LFPO 041300Z 36020KT 320V040 1200 R26/0400 +RASH BKN040TCU 17/15 Q1015 RETS M2 26791299

THE OACI CODE IS LFPO WHICH ISPARIS-ORLY AIRPORT.

All aerodromes in the world have a unique ICAO code, which is a 4-letter location indicator.

• 1st letter identifies a sector in the world (France is in sector L)
• 2nd letter identifies a country in the global sector (F for France)
• 3rd letter and 4th letter identify an aerodrome

The AUTO flag is inserted when the message contains a fully automated observation, i.e. one carried out without human intervention.

The NIL flag is inserted if the observation message is missing. It marks the end of the message.

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DATE TIME : GGGGZ

LFPO 041300Z 36020KT 320V040 1200 R26/0400 +RASH BKN040TCU 17/15 Q1015 RETS M2 2679199
OBSERVATION OF DAY NUMBER 04 OF THE MONTH AT 13:00 UTC TIME (Z OR GMT)

First 2 characters = number of the day of the current month (from 01 to 31).
The next 4 characters = the 2-digit hour (00 to 23) followed by the minutes (00 to 59) in universal time.

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WIND SPEED AND DIRECTION: DDDFF(F)GFMFM

LFPO 041300Z 36020KT 320V040 1200 R26/0400 +RASH BKN040TCU 17/15 Q1015 RETS M2 26791299

WIND FROM 360° AT 20 KNOTS (KT)

This is normally a five-digit group indicating the ten-minute average wind speed, followed without a space by an abbreviation to specify the unit used to transmit the wind speed. The first three digits indicate the wind direction. The last two, wind speed, are terminated by the wind speed unit.

Wind direction is indicated in multiples of 10° true, rounded to the nearest multiple or number. Wind direction values below 100° are preceded by a 0, and a wind blowing from true north is numbered 360. Speed values below 10 units are preceded by a 0. The wind direction is headwind when the aircraft is on the heading indicated in the METAR. In addition, if during the ten minutes preceding the observation, the maximum wind speed in the gusts (averaged over 3 seconds) exceeds the average wind speed by at least 10 knots (20 km/h) or more, this maximum speed is indicated, directly after the average speed, by the letter G followed by this maximum wind speed.

Wind direction is indicated as VRB (variable wind) instead of mean wind direction when :

• wind speed is less than 3 knots (6 km/h) and the total variation in wind direction over 10 minutes is greater than or equal to 60°.
• wind speed is greater than or equal to 3 knots (6 km/h) and the total variation in wind direction over 10 minutes is greater than or equal to 180°.

Complements :

• 00000KT = CALM WIND WHEN AVERAGE SPEED IS LESS THAN 1 KNOT
• 27010G25KT = WIND 270° 10KT WITH GUSTS TO 25KT (G=GUST)
• VRB03KT = VARIABLE DIRECTION WIND BLOWING AT 3KT
• 31005MPS = WIND 310° 5 METRE PER SECOND (MPS)

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WIND VARIABILITY: DNDNDNVDXDXDX

LFPO 041300Z 36020KT 320V040 1200 R26/0400 +RASH BKN040TCU 17/15 Q1015 RETS M2 26791299

WINDS VARYING AROUND 360° BETWEEN 320° AND 040°.

This is an optional group, i.e. it is present only to indicate variable wind.

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VISIBILITY: VVVVDV VX VXVXVXDV (NDV) OR CAVOK

LFPO 041300Z 36020KT 320V040 1200 R26/0400 +RASH BKN040TCU 17/15 Q1015 RETS M2 26791299

MINIMUM VISIBILITY OF 1200 METRES ON THE WEATHER OBSERVER’S TOUR OF THE HORIZON

The 4 digits represent visibility in meters. One or two letters can be added to define visibility in a given geographical area. In some cases, it’s possible to have more than one piece of visibility information in a row. In AUTO METARs, when the visibility sensors are located in such a way that no variation in direction can be indicated, the indicated visibility value is followed by NDV.

Complements :

• 0000 = VISIBILITY LESS THAN 50 M
• 9999 = VISIBILITY GREATER THAN OR EQUAL TO 10 KM
• 4000NE = VISIBILITY FROM 4000 M TO THE NORTHEAST (=> AVERAGE VISIBILITY ELSEWHERE = 1.5X4000 = 6000)
• 1400S 4000N = VISIBILITY OF 1400 M TO THE SOUTH BUT 4000 M TO THE NORTH 10SM = VISIBILITY OF 10 STATUTE MILES (AMERICAN MILE =1.625KM)
• 1/4SM = VISIBILITY OF 0.25 STATUTE MILE (ONE QUARTER)
• CAVOK = CEILING AND VISIBILITY OK (SEE DEFINITION BELOW)
• NSC = NO SIGNIFICANT CLOUD (NO CLOUDS BELOW 5000 FEET AND NO CUMULONIMBUS OR TOWERING CUMULUS)

CAVOK definition:
The following four conditions must be met to obtain the CAVOK:
1 – visibility greater than or equal to 10 kilometers
2 – absence of cloud below the highest of the following levels: The highest minimum sector altitude or a height of 1,500 metres (5,000 feet) above the aerodrome.
3 – absence of significant time.
4 – no cumulonimbus (CB) or towering cumulus (TCU).

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VISUAL RANGE ON RUNWAY: RDR DR/VRVRVRVRI OR RDRDR/VRVRVR VRVRVRVRVRI

LFPO 041300Z 36020KT 320V040 1200 R26/0400 +RASH BKN040TCU 17/15 Q1015 RETS M2 26791299

RVR – RUNWAY VISUAL RANGE – 400 M ON RUNWAY 26

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SIGNIFICANT PRESENT TENSE: W’W'(WW)

LFPO 041300Z 36020KT 320V040 1200 R26/0400 +RASH BKN040TCU 17/15 Q1015 RETS M2 26791299

HEAVY (+ ) SHOWERS (SH) RAIN (RA)

This is an optional group, i.e. it is present to indicate precipitation or an obscuring meteorological phenomenon. Present significant weather includes precipitation. It’s made up of one or more groups of 2 letters that define a qualifier, which you’ll find in the tables below. An intensity qualifier is sometimes added in front of the group.

FG will be included in the message when the observer observes a reduction in visibility due to the presence of water droplets or ice crystals in suspension, and when visibility is strictly below 1,000 m.

BR will be included in the message when the observer observes a reduction in visibility due to the presence of water droplets or ice crystals in suspension and when visibility is at least 1,000 m but does not exceed 5,000 m.

Intensity qualifier :

• SIGN “-” IS ADDED FOR LOW
• NO SIGN MEANS MODERATE
• +” SIGN IS ADDED FOR STRONG.

Meteorological phenomena :

• VC = IN THE VICINITY (AU VOISINAGE)
• MI = THIN (THIN)
• PR = PARTIAL OR COVERING PART OF THE AERODROME
• DR = LOW DRIFTING (DUST/SAND/SNOW)
• BL = HIGH DUST/SAND/SNOW BLOWING
• FZ = FREEZING
• RE = RECENT (RECENT)
• BC = BENCHES (BENCHES)
• SH = SHOWER
• TS = THUNDERSTORM
• XX = VIOLENT

Precipitation reaching the ground :

• RA = PLUIE (RAIN)
• SN = SNOW
• GR = GRELE (HAIL)
• DZ = DRIZZLE
• PL = ICE PELLETS
• GS = NEIGE ROULEE (GRESIL)
• SG = SNOW GRAINS
• IC = ICE CRYSTALS
• UP = UNKNOWN PRECIPITATION

Obstacles to view :

• BR = MIST
• FG = FOG
• HZ = HAZE
• FU = SMOKE
• SA = SAND
• DU = DUST
• VA = VOLCANIC ASH

Other complements :

• PO = DUST
• SS = SANDSTORM
• DS = DUSTSTORM
• SQ = SQUALLS
• +FC = TORNADO / WATERSPOUT (FUNNEL CLOUD)
• FC = FUNNEL CLOUD

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CLOUDS: NSNS HSHSHS OR VVHS HSHS OR SKC OR NSC OR NCD OR CAVOK

FPO 041300Z 36020KT 320V040 1200 R26/0400 +RASH BKN040TCU 17/15 Q1015 RETS M2 26791299

FRAGMENTED (BKN) AT 4000FT (040 ) WITH TOWERING CUMULUS CLOUDS (TCU)

Each cloud cover is made up of 3 letters giving the cloud cover area or percentage of sky covered expressed in octats. Their height is indicated in hundreds of feet with 3 digits. This is the height of the clouds in relation to the airport concerned. Several types of cloud cover can be defined in this group, in order of cloud height.

The group of three letters indicates the proportion of sky covered by clouds.

• FEW = PEU NOMBREUX / FEW = 1/8 A 2/8
• SCT = EPART / SCATTERED = 3/8 A 4/8
• BKN = FRAGMENTE / BROKEN = 5/8 A 7/8
• OVC = COVERED / OVERCAST = 8/8
• NSC = NO SIGNIFICANT CLOUDS BELOW 5000 FEET AND NO CUMULONIMBUS OR CUMULUS BUDS
• NCD = NO CLOUD DETECTED
• SKC = SKY CLEAR – CLEAR SKY, NO CLOUDS

If cumulonimbus or towering cumulus are present, CB or TCU are added.
If the sky is obscured by precipitation or fog, VV (Vertical Visibility) can be used, followed by visibility measured in hundreds of feet, or /// if visibility cannot be measured or if there is no vertical visibility.
If the station is automatic and no clouds have been detected, NCD (No Clouds Detected) is used.
When the cloud base is below station level, the cloud group is followed by the 3 bars ///.

Additional information:

• BKN025TCU = BROKEN CLOUDS AT 2500FT PRESENCE OF TOWERING CUMULUS CLOUDS
• SCT020CB = CLOUDS SPREAD AT 2000FT PRESENCE OF CUMULONIMBUS
• FEW/// = FEW CLOUDS IMPOSSIBLE TO MEASURE CLOUD HEIGHT
• VV/// = INVISIBLE SKY

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AIR AND ROSE POINT TEMPERATURE: T’T’/T’DT’D

LFPO 041300Z 36020KT 1200 R26/0400 +RASH BKN040TCU 17/15 Q1015 RETS M2 26791299
AIR TEMPERATURE IS 17° CELSIUS, ROSE POINT IS 15° CELSIUS ON THE GROUND.

Temperature values are built on 2 numbers separated by a slash /. The first value is the airfield temperature in degrees Celsius, the second is the dew point in degrees Celsius.
degrees Celsius. Observed values, with 5 as the first decimal place, are rounded up to the next whole number. The M character is used to define a negative temperature.

Additional information:

• 00/M00 = AIR TEMPERATURE AT +0°C, ROSE POINT AT -0°C (ONE IS SLIGHTLY POSITIVE EX: 0.3°C AND THE OTHER NEGATIVE EX: -0.4°C)
• M03/M05 = AIR TEMPERATURE AT -3°C, ROSE POINT AT -5°C

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PRESSURE AT SEA LEVEL: Q PHPHPHPH

LFPO 041300Z 36020KT 320V040 1200 R26/0400 +RASH BKN040TCU 17/15 Q1015 RETS M2 26791299
ATMOSPHERIC PRESSURE QNH IS 1015 HECTOPASCAL

The pressure value given in the METAR is the QNH value (atmospheric pressure of the ground brought down to the QNH value).
at sea level). The given value is on 3 and 4 digits expressed in hectopascal if the value is preceded by
if preceded by the letter Q (QNH), and in inches of mercury if preceded by the letter A (Altimeter).
Complements :

• A2985 = ALTIMETER 2985 – THIS IS THE EQUIVALENT PRESSURE AT QNH EXPRESSED IN CENTIMETERS OF
• INCH OF MERCURY. IT IS 29.85 INHG
• QFE 987 = GROUND PRESSURE WHERE QFE IS 987 HPA
• QNH 997 = QNH LESS THAN 1000 IS 3 DIGITS HERE 997 HPA

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TEMPS RECENT : REW’W’

LFPO 041300Z 36020KT 320V040 1200 R26/0400 +RASH BKN040TCU 17/15 Q1015 RETS M2 26791299
RECENT (RE) THUNDERSTORMS (TS)

Note: This is an optional group, i.e. it is present to indicate phenomena.
weather conditions.

This group is used to specify various meteorological phenomena in order to provide greater precision on the
weather conditions.
Complements :

• RERA = RECENT RAIN – PLUIE RECENTE
• WS TKOF RWY 26 = WINDSHEAR – SHEAR WIND ON TAKE-OFF RUNWAY 26

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NOTES :

LFPO 041300Z 36020KT 1200 R26/0400 +RASH BKN040TCU 17/15 Q1015 RETS M2 26791299
M2 = INCREASED VISIBILITY

This is an optional group.

LFPO 041300Z 36020KT 1200 R26/0400 +RASH BKN040TCU 17/15 Q1015 RETS M2 26791299
CONDITION OF RUNWAY 26: ICE (7) COVERING MORE THAN 51% OF THE RUNWAY (9), THICKNESS 12MM (12), UNRELIABLE COEFFICIENT OF FRICTION

This is an optional group, i.e. it is present to indicate runway status if weather conditions dictate.

CLRD//: group in place of 8 characters, associated with a track identification group, when contamination conditions have ceased to exist.
SNOCLO: replaces the runway condition group if the airfield is closed due to snow conditions