Terminal Aerodrome Forecast


  • Terminal Aerodrome Forecasts (TAFs) are concise statements of the expected meteorological conditions within a 5 SM radius from the center of an airport's runway complex
  • TAFs can be found on the National Oceanic and Atmospheric Administration's (NOAA's) website at or through use of the java tool here
    • TAFs can be retrieved in the raw coded format or a translated (decoded) format [Figure 1]
  • TAFs and Routine Aviation Weather Reports (METARs) are very similar but deviate as wind shear, temperature, icing, and turbulence groups are added to the TAF, when applicable
Figure 1: Raw or Translated TAF Query Raw or Translated TAF Query

Issuance & Validity:

  • TAFs are scheduled four times daily (0000Z, 06000Z, 1200Z, 1800Z)
  • At most locations, TAFs have a 24 hour forecast period
  • However, TAFs for some locations have a 30 hour forecast period
  • These forecast periods may be shorter in the case of an amended TAF
  • Data is forecasted
Figure 2: TAF Example
TAF Example


  • TAFs are issued in the following format:
    • [Type of Report] [ICAO Station Identifier] [Date and Time of Origin] [Valid Period Date and Time] [Forecast Meteorological Conditions]
  • TAFs use the same codes as METAR weather reports

Type of Report:

  • There are two types of TAF issuances:
    • Routine forecast issuance (TAF), and;
    • Amended forecast (TAF AMD)
  • An amended TAF is issued when the current TAF no longer adequately describes the on-going weather or the forecaster feels the TAF is not representative of the current or expected weather
    • Corrected (COR) or delayed (RTD) TAFs are identified only in the communications header which precedes the actual forecasts

GROUP 1: Message Heading:

  • Begins with the four-letter ICAO location identifier
    • In the contiguous 48 States, the 3−letter domestic station identifier is prefixed with a "K;" i.e., the domestic identifier for Seattle is SEA while the ICAO identifier is KSEA
    • Elsewhere, the first two letters of the ICAO identifier indicate what region of the world and country (or state) the station is in
    • For Alaska, all station identifiers start with “PA;” for Hawaii, all station identifiers start with “PH”
    • For a complete worldwide listing see ICAO Document 7910, Location Indicators
  • Next comes TAF and any modifiers


  • Forecast Time

    • The date and time element is the date and time the forecast is actually prepared
    • Laid out in the DTG group (dd/hh/mm)
    • Two-digit date with a four-digit time group appended with Z to denote the time (UTC)
      • Example: 091730Z
        • TAF posted on the 9th day of the month at 1730 Zulu
    • Valid times may not be for 24 hours if previously amended, corrected, or delayed
    • Military TAFs will report the forecast period prior to the date and time
    • USN/USMC will append a remark as appropriate as well
      • Example: AMD2218
        • The TAF was amended at 2218Z
  • Valid Period Date and Time:

    • The UTC valid period of the forecast consists of two four−digit sets, separated by a "/"
      • The first four−digit set is a two−digit date followed by the two−digit beginning hour, and the second four−digit set is a two−digit date followed by the two−digit ending hour
    • Although most airports have a 24−hour TAF, a select number of airports have a 30−hour TAF
      • In the case of an amended forecast, or a forecast which is corrected or delayed, the valid period may be for less than 24 hours
    • Where an airport or terminal operates on a part−time basis (less than 24 hours/day), the TAFs issued for those locations will have the abbreviated statement “AMD NOT SKED” added to the end of the forecasts
      • The time observations are scheduled to end and/or resume will be indicated by expanding the AMD NOT SKED statement
    • Expanded statements will include:
      • Observation ending time (AFT DDHHmm; for example, AFT 120200)
      • Scheduled observations resumption time (TIL DDHHmm; for example, TIL 171200Z) or
      • Period of observation unavailability (DDHH/DDHH); for example, 2502/2512)

Forecast Meteorological Conditions:

  • Forecast meteorological conditions consists of several elements which include:
    • Wind
    • Visibility
    • Weather
    • Sky condition, and
    • Optional data such as wind shear
  • Wind, visibility, and sky condition elements are always included in the initial time group of the forecast
  • Weather is included only if significant to aviation
  • If a significant, lasting change in any of the elements is expected during the valid period, a new time period with the changes is included
  • It should be noted that with the exception of a "FM" group the new time period will include only those elements which are expected to change, i.e., if a lowering of the visibility is expected but the wind is expected to remain the same, the new time period reflecting the lower visibility would not include a forecast wind
  • The forecast wind would remain the same as in the previous time period
  • Any temporary conditions expected during a specific time period are included with that time period
  • The following describes the elements in the above format:
    • GROUP 3: Wind:

      • Direction in tens of degrees from true north (first 3 digits)
      • Velocity in whole knots (next 2 digits)
      • Six-digits if wind speed is 3 digits
        • Example: 18010KT
          • wind one eight zero at one zero (wind is blowing from 180)
      • The contraction "KT" follows to denote the units of wind speed
        • Wind gusts are noted by the letter “G” appended to the wind speed followed by the highest expected gust
        • Example: 35012G20KT
          • Wind three five zero at one two gust two zero
      • Wind speed for the most recent 10 minutes is used to determine gusts and maximum peak is reported using two or three digits
      • A variable wind is noted by "VRB" where the three digit direction usually appears
      • Other countries may use KM / MPH / MPS
      • A calm wind (3 knots or less) is forecast as 00000KT
      • If wind varies by 60° or more and speed greater than 6 knots, a variable wind direction is reported as a remark
      • If wind direction is variable and speed 6 knots or less, replace wind direction with VRB, followed by wind speed in knots; or in more rare cases when it is impossible to forecast a single wind direction such as thunderstorms

      • Example: 27010KT
        • Wind from 270 at 10 knots
      • Example: WND 270V350
        • Wind variable 270 to 350
    • GROUP 4: Visibility, Weather, and Obstructions to Vision:

      Meters SM
      1,600 1
      3,200 2
      4,800 3
      6,400 4
      8,000 5
      9,600 6
      11,200 7
      12,800 8
      14,400 9
      16,000 10
    • The expected prevailing visibility up to and including 6 miles is forecast in statute miles, including fractions of miles, followed by “SM” to note the units of measure. Expected visibilities greater than 6 miles are forecast as P6SM (plus six statute miles)
      • Example: 1/2SM - visibility one−half
      • Example: 4SM - visibility four
      • Example: P6SM - visibility more than six
    • Civilian: forecasted prevailing visibility is reported in statute miles (SM)
    • Military: Forecasted prevailing visibility is reported in meters and rounded down to the nearest reportable value
    • Whenever the prevailing visibility is forecasted to be 9,000 meters or less (6 miles or less), the weather or obstructions to vision causing the reduced visibility will be included using the same notation as the METAR
    • 9999 indicates 7 miles visibility or greater is forecasted (unlimited visibility)
    • When appropriate, RVRs will follow immediately after the prevailing visibility
    • If any significant weather or obstruction to vision is forecasted it will be included after visibility using standard codes
    • Omitted if no weather is present
    • Weather Phenomena:

      • The expected weather phenomena is coded in TAF reports using the same format, qualifiers, and phenomena contractions as METAR reports (except UP). Obscurations to vision will be forecast whenever the prevailing visibility is forecast to be 6 statute miles or less. If no significant weather is expected to occur during a specific time period in the forecast, the weather phenomena group is omitted for that time period. If, after a time period in which significant weather phenomena has been forecast, a change to a forecast of no significant weather phenomena occurs, the contraction NSW (No Significant Weather) will appear as the weather group in the new time period. (NSW is included only in TEMPO groups)
      • NOTE− It is very important that pilots understand that NSW only refers to weather phenomena, i.e., rain, snow, drizzle, etc. Omitted conditions, such as sky conditions, visibility, winds, etc., are carried over from the previous time group
    • GROUP 5: Sky Condition Group:

      • Gives a description of the appearance of the sky, including cloud types/layers and sky coverage
      • Layers will be reported in ascending order up to the first overcast
      • Remember: a ceiling is defined as the first layer of broken or overcast
      • Clouds are reported by their base
      • All sky cover heights are reported in hundreds of feet above the ground level (AGL)
      • Reported in a 6-character group
      • For obscured sky:
        • VV = vertical visibility
        • VV is in hundreds of feet as well
        • More than 1 layer may be reported
      • Clouds may be followed by another modifier:
        • T = towering
        • CU = cumulus
        • CB = cumulonimbus
      • Cumulonimbus clouds (CB) are the only cloud type forecast in TAFs
      • When clear skies are forecast, the contraction “SKC” will always be used
      • The contraction “CLR” is never used in the TAF
      • When the sky is obscured due to a surface−based phenomenon, vertical visibility (VV) into the obscuration is forecast
      • The format for vertical visibility is “VV” followed by a three−digit height in hundreds of feet
        • As in METAR, ceiling layers are not designated in the TAF code
        • For aviation purposes, the ceiling is the lowest broken or overcast layer or vertical visibility into a complete obscuration
        • SKC . . . . . . . . . . . . . . “sky clear”
        • SCT005 BKN025CB . “five hundred scattered, ceiling two thousand five hundred broken cumulonimbus clouds”
        • VV008 . . . . . . . . . . . . “indefinite ceiling eight hundred"
      • Sky condition is reported in the format: Amount/Height/(Type) or Indefinite Ceiling/Height
      • The amount of sky cover is reported in eighths of sky cover, using the contractions:
        • SKC . . . . . . . . . clear (no clouds)
        • FEW . . . . . . . . >0 to 2/8
        • SCT . . . . . . . . . scattered (3/8s to 4/8s of clouds)
        • BKN . . . . . . . . . broken (5/8s to 7/8s of clouds)
        • OVC . . . . . . . . . overcast (8/8s clouds)
        • BB . . . . . . . . . . Cumulonimbus when present
        • TCU . . . . . . . . . Towering cumulus when present
      • NOTE−“SKC” will be reported at manual stations. “CLR” will be used at automated stations when no clouds below 12,000 feet are reported
      • NOTE-A ceiling layer is not designated in the METAR code. For aviation purposes, the ceiling is the lowest broken or overcast layer, or vertical visibility into an obscuration. Also there is no provision for reporting thin layers in the METAR code. When clouds are thin, that layer must be reported as if it were opaque
    • GROUP 6: Special Wind Shear:

      • The three digits before the slash indicate the altitude (AGL)
      • The characters followed the slash indicate wind direction and speed
      • Some stations will insert this group immediately after the cloud group when it is forecasted for altitude 2000' AGL and below
      • If wind cannot be forecast with accuracy, WSCONDS will be used with no numeric data
      • Group is omitted when no wind shear to be reported
        • Example: WS020/22030KT
          • Wind shear at 2000' with wind from 220 at 30 knots
        • Example: WSOCNDS
          • Wind shear present
      • Wind shear is the forecast of nonconvective low level winds (up to 2,000 feet). The forecast includes the letters “WS” followed by the height of the wind shear, the wind direction and wind speed at the indicated height and the ending letters “KT” (knots). Height is given in hundreds of feet (AGL) up to and including 2,000 feet. Wind shear is encoded with the contraction “WS,” followed by a three−digit height, slant character “/,” and winds at the height indicated in the same format as surface winds. The wind shear element is omitted if not expected to occur. WS010/18040KT − “LOW LEVEL WIND SHEAR AT ONE THOUSAND, WIND ONE EIGHT ZERO AT FOUR ZERO”
Figure 3: Weather Descriptors
Weather Descriptors
Figure 4: Aviation Services Sky Cover Contractions
Aviation Services Sky Cover Contractions

GROUP 7: Icing:

  • Consists of a six number group beginning with a 6
  • Forecasts non-thunderstorm icing
  • Omitted for no icing and repeated for multiple layers
  • 6 indicates that icing is forecasted
  • The next digit indicates the type of icing
  • The next three digits indicate the height of the base of the icing stratum in thousands of feet AGL
  • If the layer is thicker than 9,000', the icing group is repeated so that the base of the repeated group coincides with the top of the first
    • Example: 640003
      • Moderate icing at or below 100' AGL in a 3000' layer

IC Type of Icing B Type of Turbulence
Code Description Code Description
0 No icing 0 Light turbulence
1 Light icing 1 Light turbulence
2 Light icing in cloud 2 Moderate turbulence in clear air, occasional
3 Light icing in precipitation 3 Moderate turbulence in clear air, frequent
4 Moderate icing 4 Moderate turbulence in cloud, occasional
5 Moderate icing in cloud 5 Moderate turbulence in cloud, frequent
6 Moderate icing in precipitation 6 Severe turbulence in clear air, occasional
7 Severe icing 7 Severe turbulence in clear air, frequent
8 Severe icing in cloud 8 Severe turbulence in cloud, occasional
9 Severe icing in precipitation 9 Severe turbulence in cloud, frequent
X Extreme turbulence

GROUP 8: Turbulence:

  • Similar to the icing group
  • Consists of six characters following the same format, however, beginning with a 5
  • Turbulence group forecasts non-thunderstorm turbulence
  • It is implied thunderstorms will be turbulent
    • Example: 510302
      • Light turbulence from 3000' AGL in a 2000' layer

GROUP 9: Altimeter:

  • Forecasts the lowest expected altimeter setting in inches of Hg
  • Forecasted during the initial forecast and each subsequent BECMG and FM group
  • TEMPO groups do not forecast the altimeter
  • This group is useful for lost comm. in IMC
  • QNH indicates sea level pressure is being given
  • INS indicates inches
  • QNE is the standard datum plane, 29.92 in-Hg
  • QFE is the actual station pressure not corrected to sea level
  • International stations report in millibars (a.k.a. hectopascals, hPa)
  • Q indicates millibars
    • Example: QNH2981INS
      • 29.81 in-Hg
    • Example: Q1013
      • 1013 millibars

GROUP 10: Remarks:

  • Noted with an RMK
  • Includes clarifying or augmented data
  • VC is used to indicate any condition within the forecasted area, 5 to 10 SM
  • A temperature group may be forecasted to facilitate VSTOL aircraft
  • Uses the same format as a METAR temperature remark

Figure 5: Change Group Terminology
Change Group Terminology

Change Group Terminology:

  • A new line of forecasted text is started for each change group
  • More than one change group may be reported
  • From (FM) indicates a quick change
  • Becoming (BECMG) indicates a change over time
  • Temporary (TEMPO) indicates a temporary or non-permanent change to the overall weather pattern, usually no longer than 3 hours
  • The TAF is valid from the time mentioned up to, but not including, the "to" time
  • The following change indicators are used when either a rapid, gradual, or temporary change is expected in some or all of the forecast meteorological conditions. Each change indicator marks a time group within the TAF report
  • FM Group:

    • The heading FM is followed by a time (hours and minutes) indicating the forecast time
    • All previously forecasted conditions are superseded by the conditions forecasted on this line
    • FM includes all normal forecasted items as required
      • Example: FM1200
        • From 1200Z to end at 00Z
    • The FM group is used when a rapid change, usually occurring in less than one hour, in prevailing conditions is expected. Typically, a rapid change of prevailing conditions to more or less a completely new set of prevailing conditions is associated with a synoptic feature passing through the terminal area (cold or warm frontal passage). Appended to the “FM” indicator is the six−digit date, hour, and minute the change is expected to begin and continues until the next change group or until the end of the current forecast. A “FM” group will mark the beginning of a new line in a TAF report (indented 5 spaces). Each “FM” group contains all the required elements−wind, visibility, weather, and sky condition. Weather will be omitted in “FM” groups when it is not significant to aviation. FM groups will not include the contraction NSW
      • EXAMPLE−FM210100 14010KT P6SM SKC − “after 0100Z on the 21st, wind one four zero at one zero, visibility more than six, sky clear"
  • BECMG Group:

    • A four-digit time code will be used, the first two indicate the beginning hour and the next two indicate the ending hour
    • The duration of this change is normally about 2 hours, 4 at the most
    • A group not edited from a previous line will be the same
      • Example: BECMG 1718
        • From 1700Z to 1800Z
    • The BECMG group is used when a gradual change in conditions is expected over a longer time period, usually two hours. The time period when the change is expected is two four−digit groups separated by a “/”, with the beginning date and hour, and ending date and hour of the change period which follows the BECMG indicator. The gradual change will occur at an unspecified time within this time period. Only the changing forecast meteorological conditions are included in BECMG groups. The omitted conditions are carried over from the previous time group
      • NOTE−The NWS does not use BECMG in the TAF
      • EXAMPLE− OVC012 BECMG 0114/0116 BKN020 − “ceiling one thousand two hundred overcast. Then a gradual change to ceiling two thousand broken between 1400Z on the 1st and 1600Z on the 1st"
  • TEMPO Group:

    • Followed by a four-digit time group to indicate conditions that will occur briefly and will not represent a permanent change to the overall forecast weather pattern
    • Tempo is used when the condition will be in the area less than half of the time
      • Example: TEMPO 1902
        • Temporarily between 1900 up to, but not including, 0200Z
    • The TEMPO group is used for any conditions in wind, visibility, weather, or sky condition which are expected to last for generally less than an hour at a time (occasional), and are expected to occur during less than half the time period. The TEMPO indicator is followed by two four−digit groups separated by a “/”. The first four digit group gives the beginning date and hour, and the second four digit group gives the ending date and hour of the time period during which the temporary conditions are expected. Only the changing forecast meteorological conditions are included in TEMPO groups. The omitted conditions are carried over from the previous time group
      • EXAMPLE−1. SCT030 TEMPO 0519/0523 BKN030 − “three thousand scattered with occasional ceilings three thousand broken between 1900Z on the 5th and 2300Z on the 5th"
      • EXAMPLE-2. 4SM HZ TEMPO 1900/1906 2SM BR HZ − “visibility four in haze with occasional visibility two in mist and haze between 0000Z on the 19th and 0600Z on the 19th"
  • Figure 6: Airport Facility Directory (A/FD) TAF Decoder
    Airport Facility Directory (A/FD) TAF Decoder
  • Probability (PROB) Group:

    • The probability group references the chance of thunderstorms or other precipitation events occuring, along with associated weather conditions (wind, visibility, and sky conditions)
    • Begins with PROB and a two-digit percentage
      • The PROB40 group is used when the occurrence of thunderstorms or precipitation is in the 30% to less than 50% range, thus the probability value 40 is appended to the PROB contraction
    • This is followed by two four−digit groups separated by a “/”, giving the beginning date and hour, and the ending date and hour of the time period during which the thunderstorms or precipitation are expected
      • PROB30 1014 1SM -TSRA: There is roughly a 30 percent chance of 1SM visibility with thunderstorms and light rain between 1000 and 1400Z
    • NWS does not use PROB 40 in the TAF. However U.S. Military generated TAFS may include PROB40
    • PROB30 will not be shown during the first nine hours of a NWS forecast
    • EXAMPLE−PROB40 2221/2302 1/2SM +TSRA “chance between 2100Z and 0200Z of visibility one−half statute mile in thunderstorms and heavy rain.” PROB30 3010/3014 1SM RASN . “chance between 1000Z and 1400Z of visibility one statute mile in mixed rain and snow"


  • The U.S. uses the ICAO world standard for aviation weather reporting and forecasting
  • The World Meteorological Organization's (WMO) publication No. 782 "Aerodrome Reports and Forecasts" contains the base METAR and TAF code as adopted by the WMO member countries