How to decode a TAF

A Terminal Aerodrome Forecast (TAF) is a concise coded 24 to 30 hour forecast issued 4 times a day. A TAF follows a specific format, with each element providing specific information about the weather conditions at an aerodrome.

An example TAF:

TAF AMD EGTE
        041156Z 0412/0420 15006KT 4000 BR BKN006
        BECMG 0412/0415 9999 NSW BKN010 PROB30
        TEMPO 0415/0420 8000 BKN007=
        

Elements of the TAF

Identification

Report Type

Example: TAF

This indicates that the report is a routine Terminal Aerodrome Report.

Example: TAF AMD

This indicates that the report has been amended.

Location

Example: EGSS

This is the ICAO code for the aerodrome where the report was made. In this case, EGSS is the code for London Stansted.

Date and Time

Example: 130500Z

This indicates the date and time of the report in UTC (Coordinated Universal Time). In this example, 13 is the day of the month, 0500 is the time in hours and minutes, and Z indicates that the time is in UTC.

The date and time of origin is often omitted.

Forecast Validity Time

Example: 1306/1406

The time extent that the forecast is valid for, in UTC. In this example, the forecast is valid from 0600 UTC on the 13th to 0600 UTC on the 14th.

Wind

Wind Direction and Speed

Example: 31015G27KT

310 degrees, 15 knots, gusting to 27 knots.

Note: The Max wind gust is only given if it is 10 knots or more above the mean wind speed.

Variable Wind Direction

Example: 280V250

Varying between 280 and 250 degrees. This would be an extreme case of variable wind direction.

Note: Variable wind direction is given in a clockwise direction, but only when the mean speed is greater than 3 knots.

Visibility or CAVOK

Prevailing Visibility

Example: 3200

This indicates a prevailing visibility of 3200 metres.

Example: 0000

This indicates a prevailing visibility of less than 50 metres.

Example: 9999

This indicates a prevailing visibility of 10 kilometres or more.

CAVOK (Ceiling and Visibility OK)

This indicates that the visibility is 10 kilometres or more, there are no clouds below 5000 feet or below the highest minimum sector altitude, and there are no aviation significant to aviation.

Pronounced "Cav-oh-kay", this is an acronym for "Ceiling and Visibility OK".

Significant Weather

Example: +SHRA

This indicates that there is heavy rain showers at the aerodrome.

Note: a plus sign (+) indicates heavy or developed weather, and a minus sign (-) indicates light weather. No additional qualifying symbol indicates moderate weather.

Weather Descriptors

• BC Patches
• BL Blowing
• BR Mist
• DR Drifting
• DS Duststorm
• DU Widespread dust
• DZ Drizzle
• FC Funnel Cloud
• FG Fog
• FU Smoke
• FZ Freezing
• GR Hail (> 5mm)
• GS Small hail/snow pellets
• HZ Haze
• IC Ice Crystals
• MI Shallow
• PL Ice Pellets
• PO Dust devils
• PR Banks
• RA Rain
• SA Sand
• SH Showers
• SG Snow Grains
• SN Snow
• SQ Squalls
• SS Sandstorm
• TS Thunderstorm
• UP Unidentified Precipitation
• VA Volcanic Ash
• VC In vicinity

Cloud

Example: FEW005 SCT010CB BKN025

This indicates that there are a few clouds at 500 feet, scattered cumulonimbus clouds at 1000 feet, and broken clouds at 2500 feet.

Cloud parameters

• BKNBroken (5-7 oktas)
• CBCumulonimbus
• FEWFew (1-2 oktas)
• NCDNo cloud detected (AUTO METARS)
• NSCNo significant cloud none bellow 5000 ft
• OVCOvercast (8 oktas)
• SCTScattered (3-4 oktas)
• TCUTowering Cumulus
• VV010Vertical visibility of 1000 ft
• VV///Vertical visibility until obscured

Cloud figures are given in hundreds of feet above the aerodrome level.

Significant Changes

This section of the TAF is used to provide context on changes in weather conditions at the aerodrome during the forecast period.

Probability

Example: PROB30

This indicates a 30% probability of the following weather conditions occurring during the forecast period. Usually only 30% or 40% will be used.

Time

Example: 1314/1316

Given as date and time, this indicates that the following weather conditions are expected to occur between 1400 and 1600 UTC on the 13th.

Change Indicator

Example: BECMG 1314/1316

This indicates that the following weather conditions are expected to change between 1400 and 1600 UTC on the 13th.

Example: FM 250400

This indicates that the following weather conditions are expected to change from 0400 UTC on the 25th.

Occasionally, the use of TEMPO may be used. This would indicate a temporary change in weather conditions.

Met Groups

The Met group follows the change indicator, this is used to provide a forecast of the weather conditions at the aerodrome for the given time extent.

Any combinations of the wind, visibility, weather or cloud groups may be used, and CAVOK.

Example: BECMG 1314/1316 23035G50KT 3000 SHRA

This indicates that the weather conditions are expected to become worse between 1400 and 1600 UTC on the 13th, with a wind from 230 degrees at 35 knots gusting to 50 knots, a visibility of 3000 metres, and rain showers.

Examples

TAF 110500 EGPK
        110500Z 1106/1206 13010KT 9000 BKN010
        BECMG 1106/1108 BKN018 PROB30
        TEMPO 1108/1116 17025G40KT 4000 TSRA BKN012CB
        BECMG 1118/1121 3000 BR NSC=
        

TAF issued at 0500 Zulu on the 11th. Prestwick valid from oh six hundred on 11th to oh six hundred on 12th. Wind one three zero degrees ten knots. Nine kilometres visibility. Broken at one thousand feet. Becoming from oh six hundred on the 11th to oh eight hundred on the 11th, broken at one thousand eight hundred feet. 30% probability, temporarily between oh eight hundred on the 11th to sixteen hundred on the 11th, wind one seven zero degrees twenty five knots, gusting to forty knots. Four thousand metres visibility. Thunderstorm with rain. Broken cumulonimbus at one thousand two hundred feet. Becoming from eighteen hundred on the 11th to twenty one hundred on the 11th, three thousand metres visibility, mist, no significant cloud.