Explanation to some of the most common codes used in MET-reports. These are some examples of METAR, SPECI and TAF, click on the element you wish to learn more about.

METAR 191050Z VRB03KT CAVOK 03/M05 Q1014 SPECI 191107 12012G36KT 3000 SHSN SCT008 BKN015 M06/M06 Q0997

METAR 191050Z 25007KT 9999 FEW025 03/M07 Q1013 RERA METAR 191050Z 04011KT 350V090 9999 VCSH FEW020 SCT060 BKN120 08/M03 Q1005 NOSIG

METAR 191050Z 13005G18KT 9999 –SHRASN FEW015CB SCT025 BKN050 01/M08 Q1014

METAR 191050Z 01002KT 0200 FZFG R36/0350 OVC001 M02/M02 Q1007 WS RWY36

TAF (FC) 190800Z 190918 03015KT 9999 SCT012 BKN025 PROB30 TEMPO 0915 3000 -SNRA BKN008

TAF (FC) 190800Z 190918 26008KT 9999 FEW030TCU TAF (FT) 191100Z 191812 VRB05KT CAVOK

TAF (FC) 190800Z 190918 20005KT 9999 FEW025 BKN040 PROB30 TEMPO 0918 3000 -SHSN VV012

Date Time Group
The DTG (Date Time Group) when the TAF was issued, in the format DDHHMM.

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METAR
METAR is the name for weather observations that are issued at 20 and 50 minutes past each hour.  At some aerodromes they will be issued only once an hour, at 50 minutes past each hour.

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Observation time
The observation time for METAR is given in UTC.  A METAR contains actual weather observed during the observation period, which is the last 10 minutes prior to the observation time. 

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SPECI
If the weather changes significantly from the last METAR, and it is not yet time for the next one, then a SPECI is sent.  The format and contents of a SPECI is similar to a METAR.

SPECI Date/Time Group
Since a SPECI is not sent at fixed intervals, the date-time group (DTG) of the SPECI is the time when it is sent.

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TAF
TAF is the name for a forecast, and typically has a validity period of 6 to 9 hours, the validity is specified in each TAF. 

There are two types of TAFs, the most common one has the prefix (FC), but for some aerodromes there is also a TAF with considerably longer validity, this has the prefix (FT). 

Not all aerodromes have TAF issued, if there is no TAF for the aerodrome you are retrieving MET-info for, the output will say: TAF (FC) NOT AVAILABLE.  The “long” TAF (FT) is not issued for all aerodromes. 

A TAF will never contain temperature, dewpoint or QNH.

TAF validity period
The validity period of a TAF is given in the DDHHHH format, 190918 means that the TAF is for the 19^th, valid from 0900 to 1800 hours UTC.

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Wind
Wind is the mean values given in degrees and knots. 

In the case of a METAR, this is during the observation period (10 minutes). 

If the strongest wind during this period  have been 10 knots or more stronger than the mean strength, this is called a gust, and will be put in the METAR.  The wind may then be stated as 21015G25, meaning wind from 210 degrees, mean strength 15 knots with gust(s) of 25 knots during the last ten minutes.

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Variable wind
If the direction of the wind during the observation time for a METAR has varied 60 degrees or more, the wind is considered to be variable. 

If the wind strength is 3 knots or less, and the variation is more than 60 degrees the wind will be given as VRBxxKT. 

If the variations are more than 60 degrees, but less than 180 degrees, and the mean wind strength is more than 3 knots, the wind group in a METAR might look like this:  12012KT 030V190.  This means that the mean direction of the wind is from 120 degrees, but the direction varies between 030 and 190 degrees.

If the variations in the wind direction is more than 180 degrees, this is given as VRBxxKT, regardless of wind strength.

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Visibility
Visibility is given in meters. If visibility is 10 kilometers or more, the code will be 9999. 

If visibility in a sector is 5 kilometers or less, and the maximum visibility is 50% better, the compass direction to the lesser visibility will be stated as this example: 4000NE.  This means that towards north-east the visibility is 4 kilometers, and that the general visibility is 4 km plus 50%  or more.  (In this example that would be 6 kilometers).

If the minimum visibility is less than 1,5 kilometers, and the maximum visibility more than 5 kilometers, the compass direction for both sectors will be given, with the sector having the least visibility first:  1200NE 6000SW, meaning that towards north-east the visibility is 1200 meters, and towards south-west it is 6 kilometers.

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Cloud cover
Clouds are given in groups telling you how much of the sky is covered by clouds and how high those clouds are, given in feet. 

Cloud type will not be indicated unless for Cumulunimbus (CB) and towering Cumulus (TCU). 

Cloud coverage is indicated in up to three groups, depending on coverage: (Number of cloud groups may exceed three, but only if clouds CB or TCU is observed and not included in one of the other groups) 

First group will always be the lowest clouds: 1^st group: Lowest clouds, regardless of how much of the sky is covered 2^nd group: Cloud coverage of SCT, BKN or OVC. 3^rd group: Cloud coverage of BKN or OVC.

Cloud coverage is given using the following designators: FEW: 1-2 eights coverage. SCT: 3-4 eights coverage. BKN: 5-7 eights coverage. OVC: Full coverage.

Obscured clouds
If clouds are obscured, vertical visibility will be used instead.  This is indicated by VV and the vertical visibility in feet.

If the clouds are below the aerodrome level, the height of these clouds is given as ///.  FEW/// then means that there are 1-2 eights of cloud below the aerodrome.

If there are no clouds, the code SKC  (Sky Clear) is used.

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Significant weather
If significant weather that may have an affect on aircraft operations are observed or expected either at the aerodrome or at a distance from the aerodrome, this will be mentioned in METAR, SPECI or TAF.

The following table shows the different types of weather and prefixes used.

• A few examples:
  +SHRA: Heavy rain showers.
• MIFG:  Shallow fog.
• FZFG Freezing fog.
• PRFG: Partial fog, part of the runway is obscured by fog.
• -DZRA: Light drizzle and rain
• RA:  Rain
  VCSH: Showers within 8 kilometers (but not at) the aerodrome.

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RE (Recent)
A METAR contains the weather observed during the last 10 minutes prior to the observation time. 

If there have been precipitation since the last METAR, but not during the last 10 minutes, this will then be put in the METAR as recent (RE).  RERA then means recent rain.

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Trend
Trend is a short forecast given in METAR, and is used to advise expected changes within the two hours following the observation. 

Only approved aerodromes are allowed to use TREND in METARs.  In such cases as a TREND is used in the METAR, three keywords will be used:

• NOSIG: No significant change expected within the next two hours. TEMPO: indicates that there is forecast a temporary change to the weather given after the TEMPO group.
• BECMG: (becoming) indicates at least 50% chance of a gradual transition to longer lasting changes from the weather in the main part of the METAR.

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Probability
In a TAF there may be given indications for a change in the weather during the validity period of the TAF: PROB30:         30% probability of….. PROB40:         40% probability of…..

Temporarily
TEMPO followed by a four digit validity time group indicates that there is forecast a temporary change to the weather given after the TEMPO group. 

TEMPO 0915 ……  this means that between 0900 and 1500 hours the weather is forecast to be….

BECMG (becoming) followed by a four digit validity time group indicates at least 50% chance of a gradual transition to longer lasting changes from the weather in the main part of the TAF.

When BECMG from followed by a time in UTC is used this means that from the time stated a change in the weather is expected, and that nothing in the main part of the TAF (before the word BECMG) is valid after this time.

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CAVOK
CAVOK (Clouds And Visibility OK) may be used in stead of visibility and clouds if all of the following criteria are met:

• No clouds below 5000 feet or minimum sector altitude (MSA) if MSA is higher than 5000 feet.
• No CB or TCU
• No significant weather, either at the aerodrome or in the vicinity
• Visibility of 10 kilometers or more.

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Air Temperature and Dewpoint temperature
The temperature group in a METAR contains both the air temperature and the dewpoint, separated by a slash (/). 

Temperatures are given in whole degrees celsius.  Temperatures below zero are prefixed with the letter M (minus).

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Sea level Air Pressure
QNH is an international code for the air pressure at the aerodrome reduced to sea level.  In METAR this is prefixed with the letter Q if the QNH is given in hectopascal, and A if the QNH is given in inches of mercury. 

The norm is to give the QNH in hectopascals, and always in four digits, a QNH of 998 will then be Q0998 in a METAR.

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Runway Visual Range
Runway visual range is only given if the visibility and/or the RVR (Runway Visibility Range) is less than 1500 meters. 

The RVR is prefixed by the letter R followed by runway designator, then a slash (/) followed by the RVR in meters. 

The lowest value for RVR that may be stated is 50 meters, or the lowest limit for the system,  if RVR is lower than that, the letter M will be used after the slash, as in this example: R36/M050, meaning that for RWY36 the RVR is less than 50 meters.

If the RVR is more than 1500 meters, or more than the upper limit for the system used for measuring the letter P will be used to prefix the RVR value.

If the RVR is measured by instruments, it is usually the mean RVR over ten minutes that is given. 

If the RVR varies during these 10 minutes, this is indicated by giving minimum and maximum values, separated by an indicator: R36/0300V750D: Runway 36 has an RVR of minimum 300 meters, maximum 750 meters, but the RVR is going down (D).

If the RVR has a tendency either up or down, or no tendency, this is notified by the use of the letters U (up),  D (down) or N (no change). Example: R01/0900U: Mean RVR of 900 meters and the RVR is improving.

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Windshear
If windshear is observed or reported, it will be present in the METAR.  For example, WS RWY36 means that windshear for runway 36 has been observed or reported. Return