TYPES OF MESSAGES

 

A METAR, Meteorological Aviation Reports, is a routine weather report issued at hourly intervals. It is a description of the meteorological elements observed at an airport at a specific time. This report may also includes a section containing a trend forecast, which indicates changes in weather conditions expected over the two hours following.

A SPECI is an aviation special weather report issued whenever there is significant deterioration and improvement in weather conditions at an airport, such as significant changes of surface winds, visibility, cloud base height and occurrence of severe weather. a SPECI resembles a METAR, however it may not all ways contain all elements. But must contain those mentioned above.

A TAF, Terminal Area Forecast, is a weather forecast issued at 6-hour intervals. It is a description of the meteorological elements expected at an airport between specific hours; 0000Z, 0606Z, 1212Z and 1818Z on consecutive days.

NB: A TAF Forecast must not be interpreted as the weather conditions expected for  a country or areas thereof other than at the terminal area or aerodrome for which it was issued.

 

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SAMPLE OF MESSAGES

 

METAR TVSV  281300Z 12006KT 9999  BKN018 -SHRA TEMPO TSRA FEW010CB BKN012=

 

SPECI TVSV  281325Z 18006KT 6000 +TSRA FEW010CB  BKN012 BKN035=

 

TAF TVSV  281000Z VRB06KT 9999 FEW022 TEMPO 1422 +TSRA SCT010CB BKN014 BKN032=

 

 

ICAO STATION IDENTIFIERS

 

TVSV –St. Vincent- E.T. Joshua Airport

TVSB –Bequia -J.F. Mitchell Airport

TVSC –Canouan - Canouan Airport

TVSU –Union Island - Union Island Airport 

 

GMT TIME

Greenwich Mean Time Indicated by Z (Zulu)

 

WIND

The wind is give in 10s of degrees. 000 - North, 090 - East, 180 - South and 270 - West.

 

VISIBILITY:

9999 – Horizontal Visibility in excess of 10 kilometers

Any other figure will indicate the visibility is less and must be interpreted in meters.

 

PHENOMENA CODES 

Some of the more frequent weather phenomena codes used by SVGMETS.

SHRA, -SHRA, +SHRA - Showers

RA, -RA, +RA - Rain

TS,-TS, +TS - Thunderstorms

TSRA, -TSRA, +TSRA -Thunderstorms with rain or showers.

VCSH - Showers in the vicinity

FC - Funnel Cloud

HZ - Haze

 

PHENOMENA INTENSITY

THE PREFIX – (minus) signifies that the intensity is light

THE PREFIX + (plus) signifies that the intensity is heavy

NO PREFIX signifies that the intensity is moderate

 

CODES: 

VRB - VARIABLE

SKC – Sky Clear – No Clouds 

NSC – No Significant Clouds

CAVOK –Clouds And Visibility OK – Clouds above MSA* and visibility in excess of 10 KM. 

FEW – Few Clouds -1/8 -2/8 coverage of the sky.

SCT – Scattered Coverage - 3/8 – 4/8 coverage of the sky.

BKN – Broken Coverage – 5/8 – 7/8 coverage of the sky.

OVC – Overcast Sky – Entire sky covered with clouds

CB - Cumulonimbus clouds

TCU - Towering Cumulus clouds

 

N.B… A report (METAR) or forecast (TAF) may contain as many as four (4) different cloud groups.

 

* Minimum Sector Altitude is a specified height above sea level below which aircrafts cannot descend without Air Traffic Controllers permission.

 

TEMPERATURE:

These values are given in degrees Celsius (^oC).

 

QNH –MEAN SEA-LEVEL PRESSURE:

This value is given in millibars and Indicated by the prefix Q.

 

CHANGE GROUP:

TEMPO – A Temporary change of 2 hours or less is expected during the forecast period.

BCMG – Becoming, followed by the conditions expected

FM – A further change from a specific time to another time is expected

PROB30 - 30 percent probability that the conditions following will occur. the group may only be a 30 or 40 percent probability.