METAR and SPECI

Definition

METAR (Meteorological Aerodrome Report) and SPECI (Special Weather Report) are standardised messages that provide weather information observed at aerodromes. Because they are messages encoded after direct observation, they therefore constitute an observation of present, current weather, even though they may contain some supplementary or short-term trend information.

Message structure

A METAR/SPECI is encoded as follows:

Description of each group

Type

[METAR] SBGR 291200Z 11005KT 0750 0600S R10R/1200U R28R/0900N +SHRA BKN008 SCT014 FEW025 26/20 Q1017 NOSIG=
Routine observation

The first word is always METAR or SPECI, indicating the message type. A METAR message is a routine observation, usually made every hour at minute 00. A SPECI, on the other hand, indicates a special observation due to significant changes in weather conditions.

Correction of Previous Observation

If a METAR or SPECI is issued with incorrect information, a correction message will be issued containing the word COR immediately after the message type.

In our example, if it were to be corrected:

METAR [COR] SBGR 291200Z 11005KT 0750 0600S R10R/1200U R28R/0900N +SHRA BKN008 SCT014 FEW025 26/20 Q1017 NOSIG=
Correction of previous observation

Location

METAR [SBGR] 291200Z 11005KT 0750 0600S R10R/1200U R28R/0900N +SHRA BKN008 SCT014 FEW025 26/20 Q1017 NOSIG=
São Paulo/Guarulhos Airport

The four-letter ICAO code identifies the aerodrome where the observation was made.

Date and Time of Observation

METAR SBGR [291200Z] 11005KT 0750 0600S R10R/1200U R28R/0900N +SHRA BKN008 SCT014 FEW025 26/20 Q1017 NOSIG=
Observation made on the 29th of the current month at 1200Z

The next group indicates the day of the month and the time of the observation in UTC, in 24-hour format, followed by the letter Z.

Automated observation

METAR LSGG 200620Z [AUTO] VRB03KT 0900 0200NE R04/1200U R22/0900N PRFG VV002 M00/M00 Q1019 REFZDZ TEMPO 0600 FZFG=
Observation made by an automated system

Some METARs/SPECIs may include the word AUTO, indicating that the observation was made by an automated system, without direct human intervention. In these cases, this information appears immediately after the date/time.

Wind

METAR SBGR 291200Z [11005KT] 0750 0600S R10R/1200U R28R/0900N +SHRA BKN008 SCT014 FEW025 26/20 Q1017 NOSIG=
Wind from 110° at 5 knots

This group gives the mean direction from which the wind is blowing, relative to true north and rounded to the nearest 10°, followed by the mean wind speed.

The wind speed unit may be either knots (KT) or metres per second (MPS), depending on the country. In Brazil, the standard unit is the knot (KT).

There are five possible wind representations, according to the wind behaviour over the last 10 minutes before the observation:

Steady Wind (dddffKT)

If during the 10 minutes preceding the observation the wind blows with constant direction and speed, it is classified as steady. It is represented by three digits for the direction (in degrees) and two digits for the speed (in knots), followed by the unit KT.

Variable Wind, Undefined (VRBffKT)

If during the 10 minutes preceding the observation the wind shows a direction variation equal to or greater than 60° but less than 180°, and the speed is below 3 knots, it is classified as variable (undefined). In this case, the direction is represented by VRB, followed by the speed in knots.

Variable Wind, Defined (dddVddd)

If during the 10 minutes preceding the observation the wind shows a direction variation equal to or greater than 60° and the speed is equal to or greater than 3 knots, with the two extreme directions between which the wind has varied being observed, it is classified as variable (defined). In this case, the direction is represented by two three-digit groups separated by the letter V, indicating the lower and upper limits of the wind direction variation in a clockwise direction.

Calm Wind (00000KT)

The wind is classified as calm when the mean wind speed is below 1 knot. In this case, the direction is represented by 000 and the speed by 00, followed by the unit KT.

Gusts (...GffKT)

If during the 10 minutes preceding the observation the wind shows gusts, that is, rapid and momentary variations in wind speed exceeding the mean speed by 10 knots or more, it is classified as gusting. In this case, the maximum gust speed is given in two digits immediately after the mean speed and the letter G.

Wind of 100 knots or more (...P99KT)

For mean wind speeds equal to or greater than 100 knots, the speed is represented by P99 ("plus 99").

Horizontal Visibility

METAR SBGR 291200Z 11005KT [0750 0600S] R10R/1200U R28R/0900N +SHRA BKN008 SCT014 FEW025 26/20 Q1017 NOSIG=
Prevailing horizontal visibility of 750 metres, visibility of 600 metres to the south

This group gives the prevailing horizontal visibility in metres. In some cases, there may be additional information about visibility in specific sectors.

If the horizontal visibility is not the same in different directions and differs from the prevailing visibility, the visibility in specific sectors will be given after the prevailing visibility, referring to the cardinal (N, E, S, W) or intercardinal (NE, SE, SW, NW) points.

Visibility is reported as follows:

1. increments of 50 m up to 800 m;
2. increments of 100 m for values from 800 to 5000 m;
3. increments of 1000 m for values from 5000 to 9000 m; and
4. 9999 to indicate 10 km or more.

Runway Visual Range (RVR)

METAR SBGR 291200Z 11005KT 0750 0600S [R10R/1200U R28R/0900N] +SHRA BKN008 SCT014 FEW025 26/20 Q1017 NOSIG=
RVR on runway 10R of 1200 metres, upward tendency; RVR on runway 28R of 900 metres, no change

Runway visual range (RVR) is a measure of the distance along the runway over which a pilot can see the runway markings or approach lights. In a METAR/SPECI, RVR is given for specific runways, followed by the tendency.

The value is the mean obtained over the 10 minutes preceding the observation, and may be lowered if there is a considerable deterioration in visual range conditions.

RVR is reported as follows:

1. increments of 25 m for values up to 400 m;
2. increments of 50 m for values from 400 to 800 m; and
3. increments of 100 m for values above 800 m.

Additionally, if the RVR is greater than the maximum value observable by the equipment, it will be given as Pxxxx, where xxxx is the maximum measurable value. Likewise, when the RVR is below the minimum observable value, it will be given as Mxxxx, where xxxx is the minimum measurable value.

A tendency, also observed over this 10-minute period, may be given in three different ways:

• U (up): upward tendency of the visual range;
• D (down): downward tendency of the visual range;
• N (no change): no significant change in the visual range.

Weather Phenomena

METAR SBGR 291200Z 11005KT 0750 0600S R10R/1200U R28R/0900N [+SHRA] BKN008 SCT014 FEW025 26/20 Q1017 NOSIG=
Heavy rain shower

All weather phenomena observed at the aerodrome and in its vicinity that are significant to flight operations are indicated by standardised codes.

The phenomena group is divided into three parts:

1. intensity or proximity qualifier (as applicable);
2. abbreviation of the phenomenon descriptor; and
3. abbreviation of the weather phenomenon or combinations thereof.

Table of Qualifiers, Descriptors and Weather Phenomena

Portuguese English Spanish

Intensidade ou Proximidade	Descritor	Precipitação	Obscurecedor	Outros
- Leve	MI Baixo	DZ Chuvisco	BR Névoa Úmida	PO Poeira/Areia em Redemoinhos
Moderada (sem sinal)	BC Bancos	RA Chuva	FG Nevoeiro	SQ Tempestades
+ Forte/Bem desenvolvido	PR Parcial	SN Neve	FU Fumaça	FC Funil (tornado ou tromba d'água)
VC Na vizinhança	DR Flutuante Baixo	SG Grãos de Neve	VA Cinzas Vulcânicas	SS Tempestade de Areia
	BL Soprada	PL Pelotas de Gelo	DU Poeira em área extensa	DS Tempestade de Poeira
	SH Pancada(s)	GR Granizo	SA Areia
	TS Trovoada	GS Granizo Pequeno	HZ Névoa Seca
	FZ Congelante	UP Precipitação Desconhecida

Intensity or Proximity	Descriptor	Precipitation	Obscuration	Other
- Light	MI Shallow	DZ Drizzle	BR Mist	PO Dust/Sand Whirls
Moderate (no sign)	BC Patches	RA Rain	FG Fog	SQ Squalls
+ Heavy/Well developed	PR Partial	SN Snow	FU Smoke	FC Funnel (tornado or waterspout)
VC In the vicinity	DR Low Drifting	SG Snow Grains	VA Volcanic Ash	SS Sandstorm
	BL Blowing	PL Ice Pellets	DU Widespread Dust	DS Duststorm
	SH Shower(s)	GR Hail	SA Sand
	TS Thunderstorm	GS Small Hail	HZ Haze
	FZ Freezing	UP Unknown Precipitation

Intensidad o Proximidad	Descriptor	Precipitación	Obscurecedor	Otros
- Débil	MI Baja	DZ Llovizna	BR Neblina	PO Remolinos de Polvo/Arena
Moderada (sin signo)	BC Bancos	RA Lluvia	FG Niebla	SQ Turbonadas
+ Fuerte/Bien desarrollado	PR Parcial	SN Nieve	FU Humo	FC Embudo (tornado o tromba marina)
VC En las proximidades	DR Bajo Deriva	SG Granos de Nieve (cinarra)	VA Ceniza Volcánica	SS Tempestad de Arena
	BL Soplando	PL Hielo Granulado	DU Polvo Extendido	DS Tempestad de Polvo
	SH Chubasco(s)	GR Granizo	SA Arena
	TS Tormenta	GS Granizo Pequeño	HZ Calima
	FZ Engelante	UP Precipitación Desconocida

Cloud Cover

METAR SBGR 291200Z 11005KT 0750 0600S R10R/1200U R28R/0900N +SHRA [BKN008 SCT014 FEW025] 26/20 Q1017 NOSIG=
Broken at 800 feet, scattered at 1400 feet, few clouds at 2500 feet.

Cloud cover is represented by standardised codes indicating the amount of cloud present in the sky and the height of the cloud base in hundreds of feet above ground level (AGL).

When convective clouds occur, such as cumulonimbus (CB) or cumulus congestus of great vertical extent (TCU), this information is appended to the end of the cloud cover group.

Convective Clouds

CB and TCU clouds are indicative of significant atmospheric instability and may be associated with severe weather phenomena such as thunderstorms, turbulence and hail. The presence of these clouds is crucial to the safety of flight operations and requires special attention from pilots and air traffic controllers. Flying near or through these clouds can pose considerable risks due to the adverse conditions they can generate, not only for the aircraft but also for the passengers and crew on board.

It is important to note that a TCU generally develops into a CB, which is why it is important to report both types in the METAR/SPECI message.

See below an illustrative image of these clouds:

When there are no clouds of operational significance, no restriction on vertical visibility, and the term CAVOK is not appropriate, the code NSC (Nil Significant Cloud) is used.

If an automated system issues the METAR/SPECI and no clouds can be detected, the code NCD (No Cloud Detected) is used. Likewise, if the system detects the presence of CB or TCU clouds but cannot determine the base height, the height is given as ///. Additionally, if thunder is heard or lightning is detected, but it is not possible to identify the amount and base height of CB clouds because the sky is obscured or covered by a very low cloud layer, the code /////CB is used.

Cloud Cover Table

Vertical Visibility

METAR LSZH 200150Z AUTO VRB02KT 0750 0600S R04/1200U R22/0900N PRFG [VV003] M02/M02 Q1020 NOSIG=
Vertical visibility of 300 feet

When the sky is obscured by clouds or other weather phenomena, vertical visibility is given in the METAR/SPECI. Vertical visibility is defined as the vertical visual range into an obscuring medium.

Vertical visibility is given in hundreds of feet, preceded by VV, up to a limit of 2000 feet.

When vertical visibility information is not available or cannot be determined by an automated system, the code VV/// is used.

CAVOK

METAR SBGR 291200Z 11005KT [CAVOK] 26/20 Q1017 NOSIG=
Clear sky and good visibility.

The term CAVOK (Ceiling And Visibility OK) replaces the groups for horizontal visibility, runway visual range, present weather, clouds or vertical visibility when the following conditions occur simultaneously at the time of observation:

1. horizontal visibility of 10 km or more;
2. no significant clouds; and
3. no significant weather phenomena that could affect flight safety.

Temperature and Dew Point

METAR SBGR 291200Z 11005KT 0750 0600S R10R/1200U R28R/0900N +SHRA BKN008 SCT014 FEW025 [26/20] Q1017 NOSIG=
Temperature of 26°C and dew point of 20°C

This group gives the air temperature and the dew point temperature, both in degrees Celsius, separated by a slash (/).

When values are in the range between -9°C and 9°C, the value is preceded by a zero (0). Negative values are indicated by the letter M (minus) before the number.

Pressure

METAR SBGR 291200Z 11005KT 0750 0600S R10R/1200U R28R/0900N +SHRA BKN008 SCT014 FEW025 26/20 [Q1017] NOSIG=
Sea level pressure of 1017 hPa.

This group gives the atmospheric pressure at sea level, expressed in hectopascals (hPa), preceded by the letter Q. The value is rounded down to the nearest whole hectopascal and, if it is less than 1000 hPa, it is preceded by a zero.

Supplementary Information

METAR SBGR 291200Z 11005KT 0750 0600S R10R/1200U R28R/0900N +SHRA BKN008 SCT014 FEW025 26/20 Q1017 [NOSIG]=
No significant change expected.

Various additional information may be included at the end of the METAR/SPECI, such as weather trends, special remarks or warnings.

• Recent Weather

  Information on recent weather phenomena that occurred at the aerodrome or in its vicinity is indicated by the standardised codes, preceded by the abbreviation RE.

• Wind Shear

  The presence of wind shear on approach or take-off on a given runway is indicated by the abbreviation WS Rxx, where xx is the runway number. If the wind shear affects all runways, the abbreviation used is WS ALL RWY.

• Trend Forecast

  When a significant change in weather conditions is forecast, it is indicated by TEMPO if temporary, or BECMG if the change is permanent. These forecasts are followed by the standard groups for weather phenomena, visibility, cloud cover, among others.

• No Significant Change

  The abbreviation NOSIG indicates that no significant changes in weather conditions are expected in the next hour.

• Other remarks

  Any other remark relevant to flight operations may be included at the end of the METAR/SPECI after RMK. The text after RMK does not follow a standardised format and may vary from one weather station to another.

End of Message

METAR SBGR 291200Z 11005KT 0750 0600S R10R/1200U R28R/0900N +SHRA BKN008 SCT014 FEW025 26/20 Q1017 NOSIG[=]
End of message.

The equals sign (=) indicates the end of the message.

Practical METAR/SPECI Examples