Aerodrome Forecast (TAF) A TAF is a coded statement of meteorological conditions expected at an aerodrome and within a radius of five nautical miles of the aerodrome reference point. Explanation of TAF Elements Identifier and Description TAF - Aerodrome Forecast TAF AMD - Amended Aerodrome Forecast TAF COR - Corrected Aerodrome Forecast TAF .. CNL - Cancels Aerodrome Forecast TAF .. NIL - Aerodrome Forecast will not be issued PROV TAF - Provisional Aerodrome Forecast Location The location is given by either an ICAO location indicator or an approved Airservices Australia abbreviation. Issue Time The issue time of the TAF is expressed in a six-figure group followed by the code letter Z, e.g. 202230Z, which gives an issue time of 2230 on the 20th day of the month UTC. Validity The period of validity is given in the format ddhh/ddhh, where dd is day of the month and hh is hour UTC, e.g. 2100/2206, which gives a 30 hour validity period from 0000 the 21st to 0600 on the 22nd UTC. Note that 00 is used to indicate periods of validity beginning at 0000 UTC; and 24 is used to indicate periods of validity ending at 2400 UTC. Wind The wind direction is given in degrees True, rounded to the nearest 10 degrees. A variable wind direction is given as VRB (used when the forecasting of a mean wind direction is not possible). The wind speed is given in knots (KT). The maximum wind gust is included, after the letter G, if it is expected to exceed the mean by 10 knots or more, e.g. a wind direction 280° True, with a mean speed of 20 knots, and a maximum gust of 30 knots, is given as 28020G30KT Visibility The horizontal visibility is given in metres in increments of 50 metres when visibility is forecast to be less than 800 metres; in increments of 100 metres when forecast to be 800 metres or more but less than 5,000 metres; and in increments of 1,000 metres when forecast to be 5,000 or more but less than 10,000 metres . Visibility is always given in a four figure group: eg 500 metres is given as 0500. Forecast visibilities of 10 kilometres or more are given as 9999. Visibility is not given when CAVOK is forecast. Weather Forecast weather is expressed using the following abbreviations: MI - shallow BC - patches PR - partial DR - drifting BL - blowing SH - showers FZ - freezing TS - thunderstorm DS - duststorm GS - small hail/snow pellets DZ - drizzle FG - fog RA - rain BR - mist GR - hail FU - smoke SN - snow HZ - haze SG - snow grains PO - dust devil DU - dust SQ - squall SA - sand FC - funnel cloud SS - sandstorm VA - volcanic ash IC - ice crystals PL - ice pellets Intensity is indicated for precipitation, blowing dust/sand/snow, duststorms and sandstorms. In these cases, the weather group is prefixed by - for light and + for heavy; moderate intensity has no prefix, e.g. +TSRA means thunderstorm with heavy rain; DZ means moderate drizzle; -RA means light rain. After a change group, if the weather ceases to be significant, the weather group is replaced by NSW (nil significant weather) or CAVOK if appropriate. Cloud Cloud information is given from the lowest to the highest layers in accordance with the following rule: 1st group: the lowest layer regardless of amount. 2nd group: the next layer covering more than 2 oktas. 3rd group: the next higher layer covering more than 4 oktas. Extra group for cumulonimbus and towering cumulus when forecast but not at any of the layer heights given above. Cloud amount is given using the following abbreviations: SKC - sky clear FEW - few (1 to 2 oktas) SCT - scattered (3 to 4 oktas) BKN - broken (5 to 7 oktas) OVC - overcast (8 oktas) NSC - nil significant cloud Cloud height is given as a three-figure group in hundreds of feet above the aerodrome, e.g. cloud at 700 feet above the aerodrome is shown as 007. Cloud type is identified only for cumulonimbus and towering cumulus, e.g. FEW030CB, SCT040TCU. CAVOK The abbreviation CAVOK (Ceiling and Visibility and weather OK) is used when the following conditions are forecast simultaneously: Visibility is 10 kilometres or more, No cloud below 5000 feet or the highest 25 nautical mile minimum sector altitude, whichever is the higher; and no cumulonimbus or towering cumulus at any height, No weather of significance to aviation, i.e. none of the weather listed in the weather table Significant Changes and Variations (FM, BECMG, INTER, TEMPO) Significant changes and variations will be included when the changes and variations are expected to satisfy the amendment criteria. It should be noted that these changes relate to improvements as well as deteriorations. The term FM is used when one set of prevailing weather conditions is expected to rapidly change to a different set of prevailing weather conditions. The indicator is the beginning of a self-contained forecast, with the new conditions applying until the end period of the forecast or until the commencement time of another FM or BECMG group. The term BECMG is used when one set of prevailing weather conditions is expected to gradually change to a different set of prevailing weather conditions. The indicator is the beginning of a self-contained forecast, with the new conditions applying until the end period of the forecast, or until the commencement time of another BECMG or FM group. Following any change group (FM or BECMG) there will be information on wind, visibility, weather and cloud; except when CAVOK is given or when fog is forecast. Following any change group (FM or BECMG) where there is nil significant weather forecast the abbreviation NSW is used. In some cases where the sky is forecast to be clear after a change group the abbreviation SKC is used. The terms TEMPO and INTER are used to indicate significant temporary or intermittent variations from the prevailing conditions previously given in the TAF. TEMPO is used for periods of 30 minutes or more but less than 60 minutes. INTER is used for periods less than 30 minutes. Change and variation groups (FM, BECMG, TEMPO, INTER) are not introduced until all information necessary to describe the initial forecast conditions of wind, visibility, weather and cloud have been given. Variation groups (TEMPO, INTER) follow at the end of all change groups (FM, BECMG) and before any PROB or TURB. PROB The term PROB[%] is used if the estimated probability of occurrence is 30 or 40 percent (probabilities of less than 30% are not given), and is only used with reference to thunderstorms or poor visibility (less than the alternate minimum) resulting from fog, mist, dust, smoke or sand. If the estimated probability of occurrence is greater than or equal to 50 percent, reference is made to the phenomenon in the forecast itself, not by the addition of a PROB. When using PROB with thunderstorms, INTER and TEMPO are also included whenever possible to indicate the probable duration. Where PROB is used without one of these, the likely period of occurrence will be deemed to be one hour or more. For example: PROB30 INTER 1205/1211 5000 -TSRA BKN040CB indicates a 30% probability of deteriorations of less than 30 minutes due to thunderstorms with light rain between 0500 and 1100 UTC on the 12th. PROB40 TEMPO 1102/1113 3000 TSRA BKN040CB indicates a 40% probability of deteriorations of 30 minutes or more but less than 60 minutes due to thunderstorms with moderate rain between 0200 and 1300 UTC on the 11th. PROB30 1005/1014 1000 +TSRA BKN040CB indicates a 30% probability of deteriorations of one hour or more due to thunderstorms with heavy rain between 0500 and 1400 UTC on the 10th. RMK RMK (remarks) precedes Turbulence (if forecast) and Temperatures and QNH Turbulence. Special reference is made in TAF to hazardous turbulence that may endanger aircraft or adversely affect their safe or economic operation. The TAF contains information on commencement time (FMddhhmm), the expected intensity (moderate [MOD] or severe [sEV]) and the vertical extent (BLW.... FT). TILLddhhmm is used to indicate the cessation of the turbulence when this is expected before the end of the TAF validity. Air Temperature Temperature, preceded by the letter T, is given in whole degrees celsius using two figures. If the temperature is below zero Celsius, the value is prefixed by the letter M (minus). In Australia, forecasts of air temperature are given at three-hourly intervals, for a maximum of nine hours, from the time of commencement of validity of the forecast. They are given for the times HH, HH+3, HH+6 and HH+9, where HH is the time of the commencement of the TAF validity. They are point forecasts for these times but are valid for, in the case of the first value, ninety minutes after the time point HH; and, for subsequent values, ninety minutes each side of the time point. QNH QNH, preceded by the letter Q, is given in whole hectopascals using four figures. In Australia, forecasts of QNH are given at three-hourly intervals, for a maximum of nine hours, from the time of commencement of validity of the forecast. They are given for the times HH, HH+3, HH+6 and HH+9, where HH is the time of the commencement of the TAF validity. They are point forecasts for these times but are valid for, in the case of the first value, ninety minutes after the time point HH; and, for subsequent values, ninety minutes each side of the time point. TAF Examples TAF YMAY 022230Z 0300/0312 35010KT CAVOK FM030800 31018KT 9999 SHRA BKN025 OVC100 INTER 0308/0312 31020G40KT 3000 +TSRA BKN010 SCT040CB RMK FM030600 MOD TURB BLW 5000FT T 23 24 28 33 Q 1012 1013 1014 1009 Decoded: TAF - Aerodrome Forecast YMAY - ICAO location indicator for Albury Airport 022230Z - TAF issued at 2230 on the 2nd day of the month UTC 0300/0312 - Validity period of TAF is from 0000 to 1200, on the 3rd day of the month UTC 35010KT - Wind will be from the north (350 degrees True) at 10 knots CAVOK - Cloud, visibility and weather ok FM030800 - Significant changes to the mean conditions are expected to commence from 0800 on the 3rd UTC, and to persist (at least) until the end of the forecast period Note that there will be intermittent variations to these new mean conditions (refer INTER below) 31018KT - Wind will be from the northwest (310 degrees True) at 18 knots 9999 - Visibility will be 10 kilometres or more SHRA - Weather will be moderate showers of rain BKN025 - Cloud will be broken (5 to 7 oktas) with base at 2500 feet above the aerodrome OVC100 - There will also be overcast cloud (8 oktas) with base at 10000 feet INTER 0308/0312 - There will be intermittent (periods of less than 30 minutes) variations to the previously given mean conditions. Period of INTER is 0800 to 1200 on the 3rd UTC 31020G40KT - Intermittently the wind will be from the northwest (310 degrees True) at 20 knots gusting to 40 knots 3000 - Visibility will be 3000 metres +TSRA - Weather will be thunderstorms with heavy rain BKN010 - Cloud will be broken (5 to 7 oktas) with base at 1000 feet above the aerodrome SCT040CB - There will also be 3 to 4 oktas of cumulonimbus cloud with base at 4000 feet RMK - Remarks section follows FM030600 MOD TURB BLW 5000FT - From 0600 on the 3rd UTC, expect moderate turbulence below 5000 feet T 23 24 28 33 - Forecast air temperatures at 00, 03, 06 and 09 UTC are 23, 24, 28 and 33 Q 1012 1013 1014 1009 - Forecast QNH at 00, 03, 06 and 09 UTC are 1012, 1013, 1014 and 1009. TAF COR YMLT 212240Z 2200/2218 31015G28KT 6000 -RA BKN010 OVC100 TEMPO 2209/2218 2000 +TSRA BKN005 SCT040CB RMK T 25 21 18 15 Q 1014 1013 1013 1011 Decoded: TAF - Aerodrome Forecast COR - This TAF is a correction to the previously issued TAF YMLT - ICAO Location Indicator for Launceston Airport 212240Z - TAF issued at 2240 on the 21st day of the month UTC 2200/2218 - Validity period of TAF is from 0000 until 1800 on the 22nd of the month UTC 31015G28KT - Mean wind is expected to be from 310 degrees True at 15 knots with gusts to 28 knots 6000 - Visibility will be 6000 metres -RA - Weather will be light rain BKN010 - Cloud will be broken (5 - 7 octas), with base at 1000 feet above the aerodrome OVC100 - There will also be overcast cloud, with base at 10,000 feet above the aerodrome TEMPO 2209/2218 - There will be temporary variations (periods of 30 to 60 minutes), to the previously given mean conditions, during the period 0900 to 1800 on the 22nd. 2000 - Visibility will be 2000 metres +TSRA - Weather will be thunderstorms with heavy rain showers BKN005 - There will be broken (5 to 7 oktas) cloud with base at 800 feet above the aerodrome SCT040CB - There will also be scattered (3 to 4 oktas) cumulonmbus cloud with base at 2000 feet above the aerodrome RMK - Remarks section follows T 25 21 18 15 - Forecast air temperatures at 06, 09, 12 and 15 UTC are 25, 21, 18 and 15 Q 1014 1013 1013 1011 - Forecast QNH at 06, 09, 12 and 15 UTC are 1014, 1013, 1013 and 1011 TAF AMD YMML 292330Z 3000/3106 14008KT 9999 NSW SCT030 FM301100 14003KT 3000 HZ BKN009 PROB40 3017/3023 0400 FG RMK T 14 15 17 14 Q 1016 1014 1013 1014 Decoded: TAF - Aerodrome Forecast AMD - This TAF amends the previously issued TAF YMML - ICAO location indicator for Melbourne Airport 292230Z - TAF issued at 2230 on the 29th day of the month UTC 3000/3106 - Validity period of TAF is from 0000 on the 30th until 0600 on the 31st UTC 14008KT - Mean wind is expected to be from the southeast (150 degrees True) at 8 knots 9999 - Visibility will be 10 kilometres or more NSW - There will be nil significant weather SCT030 - Cloud will be scattered (3 to 4 oktas), with base at 3000 feet above the aerodrome FM301100 - Significant new mean conditions are expected from 1100 on the 30th UTC; 14003KT - Mean wind is expected to be from 150 degrees True at 3 knots 3000 - Visibility will be 3 kilometres HZ - Weather will be haze BKN009 - Cloud will be broken (5 to 7 oktas), with base at 900 feet above the aerodrome PROB40 3017/3023 - There is a 40% probability of conditions being the following during the period 1700 to 2300 on the 30th: 0400 - Visibility of 400 metres FG - Fog RMK - Remarks section follows T 14 15 17 14 - Forecast air temperatures at 00, 06, 09 and 12 UTC are 14, 15, 17 and 14 Q 1016 1014 1013 1014 - Forecast QNH at 00, 06, 09 and 12 UTC are 1016, 1014, 1013 and 1014
