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AERODROME FORECASTS

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Title: AERODROME FORECASTS


1
AERODROME FORECASTS
PART B TAF
  • FOURTH EDITION
  • August 2005

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2
AERODROME FORECASTS - TAF
  • Aerodrome forecasts (TAFs) are complete
    descriptions of the meteorological elements
    expected at and over the aerodrome throughout the
    whole of the forecast period.

3
AERODROME FORECASTS - TAF
  • Aerodrome forecasts (TAFs) are complete
    descriptions of the meteorological elements
    expected at and over the aerodrome throughout the
    whole of the forecast period.
  • TAFs describe the forecast prevailing conditions
    at an aerodrome and cover a period of 9 to 24
    hours.

Short TAF
Long TAF
4
AERODROME FORECASTS - TAF
  • TAF contain specific information presented in a
    fixed order
  • IDENTIFICATION GROUPS
  • SURFACE WIND
  • PREVAILING VISIBILITY
  • WEATHER
  • CLOUD (or vertical visibility)
  • EXPECTED SIGNIFICANT CHANGES

5
AERODROME FORECASTS - TAF
  • IDENTIFICATION GROUPS
  • This contains seven parts
  • The aerodrome forecast code name (TAF) included
    at the beginning of an individual aerodrome
    forecast and at the beginning of a bulletin
    consisting of one or more aerodrome forecasts
  • The code word AMD if the TAF amended
  • The code word COR if the TAF corrected
  • The ICAO location indicator of the aerodrome (ex.
    OJAM)
  • The date and time of issue of the forecast
  • The period covered by the forecast
  • The code word CNL if the TAF is cancelled.

6
AERODROME FORECASTS - TAF
  • Example1
  • TAF AMD OJAM 171620Z 171212 CNL
  • Example2
  • TAF OJAM 171125Z 171212

7
AERODROME FORECASTS - TAF
  • SURFACE WIND
  • Normally this is a five-figure group followed
    by an abbreviation to indicate the wind speed
    units used. The first three figures indicate the
    wind direction from true north and the last two
    the mean wind speed. (ex. 32014KT)
  • If the wind is expected to be gusty and the
    maximum gust speed exceed the mean speed by 10 kt
    or more. (ex. 32014G28KT)
  • The encode VRB is used only if
  • The mean wind speed is less than 3 kt. or
  • The variation of wind direction is 180 or more.
    or
  • It is impossible to forecast a single wind
    direction, for example during a thunderstorm.
  • When a wind speed of 100 kt or more is forecast,
    it should be indicated as P99 kt. (ex. 320P99KT)

8
AERODROME FORECASTS - TAF
  • Example
  • TAF OJAM 171125Z 171212 32012G25KT

9
AERODROME FORECASTS - TAF
  • VISIBILITY
  • Forecast prevailing visibility is encoded as a
    four-figure group, the figures are the expected
    values in meters.
  • If the prevailing visibility is 10 km or greater,
    it is encoded as 9999.

10
AERODROME FORECASTS - TAF
  • Example
  • TAF OJAM 171125Z 171212 32012G25KT 5000

11
AERODROME FORECASTS - TAF
  • WEATHER
  • Forecast weather phenomena given in the next
    table, which are expected to cause a significant
    change in visibility, using one or more, up to
    maximum of three.
  • If no significant weather, as defined above, the
    group is omitted.
  • If the weather stop to be significant, the
    weather group is replaced by NSW (Nil Significant
    Weather)

12
AERODROME FORECASTS - TAF
QUALIFIER QUALIFIER WEATHER PHENOMENA WEATHER PHENOMENA WEATHER PHENOMENA
Intensity or proximity Descriptor Precipitation Obscuration Other
- Light Moderate (no qualifier) Heavy VC (in the vicinity) MI Shallow BC Patches PR Partial DR Low drifting BL Blowing SH Shower(s) TS Thunderstorm FZ Freezing DZ Drizzle RA Rain SN Snow SG Snow grains IC Ice crystals PL Ice pellets GR Hail GS Small hail UP Unknown precipitation BR Drizzle FG Fog FU Smoke VA Volcanic ash DU Widespread dust SA Sand HZ Haze PO Dust/sand whirls SQ Squalls FC Funnel cloud(s) SS Sandstorm DS Dust storm
13
AERODROME FORECASTS - TAF
  • Example
  • TAF OJAM 171125Z 171212 32012G25KT 5000 SHRA

14
AERODROME FORECASTS - TAF
  • CLOUD or VERTICAL VISIBILITY)
  • The group of cloud information is consists of six
    characters
  • The first three indicating the expected cloud
    amount, using the abbreviations
  • FEW Few 1/8 to 2/8
  • SCT Scattered 3/8 to 4/8
  • BKN Broken 5/8 to 7/8
  • OVC Overcast 8/8
  • The last three figures indicate the expected
    height of the base of cloud, in units of 100 ft.
  • Only the cloud type cumulonimbus (CB) is
    indicated.

15
AERODROME FORECASTS - TAF
  • CLOUD or VERTICAL VISIBILITY)
  • When the forecaster expects more than one layer
    or mass of cloud, additional cloud groups are
    given in accordance with the following
  • The lowest individual layer of any amount (FEW,
    SCT,BKN,OVC)
  • The next individual layer covering more than 2/8
    (SCT,BKN,OVC)
  • The next individual layer covering more than 4/8
    (BKN,OVC)
  • Cumulonimbus cloud (CB) when forecast, if not
    already in one of the groups above.

The number of groups will not exceed three except
that CB will always be included if forecast
16
AERODROME FORECASTS - TAF
  • When clear sky is forecast, the abbreviation SKC
    is used.
  • When the sky is expected to be obscured and
    information on vertical visibility is available
    (VVhshshs).
  • CAVOK shall be used if
  • Visibility is 10 km or more
  • No clouds below 5000 ft, and no CB
  • No significant weather phenomena is indicated.
  • When no cumulonimbus or clouds below 5000 ft,
    NSC (Nil Significant Cloud) is used

17
AERODROME FORECASTS - TAF
  • Example
  • TAF OJAM 171125Z 171212 32012G25KT 5000 SHRA
    FEW005 FEW010CB SCT018 BKN025
  • TAF OJAM 171125Z 171212 32012G25KT CAVOK
  • TAF OJAM 171125Z 171212 32012G25KT 5000 HZ NSC

18
AERODROME FORECASTS - TAF
  • INDICATION OF SIGNIFICANT CHANGES
  • When one set of prevailing weather conditions is
    expected to change significantly, the time
    indicator group FMGGgg is used to indicate the
    beginning of a self contained part of the
    forecast.
  • The groups BECMG GGGeGe indicate a regular or
    irregular change to the forecast meteorological
    conditions expected within the period GG to GeGe.
    This period will normally not exceed two hours
    but in any case will
  • never be more than four hours.

19
AERODROME FORECASTS - TAF
  • The groups TEMPO GGGeGe indicate temporary
    fluctuations in the forecast meteorological
    conditions which may occur at any time during
    the period GG to GeGe. The meteorological
    conditions following these groups are expected to
    last less than one hour in each instance and in
    aggregate less than half the period GG to GeGe.

20
AERODROME FORECASTS - TAF
  • When the confidence in forecasting alternative
    values is not high, yet the forecast element
    being considered is significant to aircraft
    operations, the groups PROBC2C2 GGGeGe are used.
  • - C2C2 indicates the percentage
    probability of occurrence, with only the values
    30 or 40
  • - The number of change and probability
    groups should not exceed five groups

21
  • Example
  • TAF OJAM 171125Z 171212 32012G25KT 5000 SHRA
    FEW005 FEW010CB SCT018 BKN025 PROB30 TEMPO 0512
    31010KT 7000 NSC

22
AERODROME FORECASTS - TAF
THIRD EDITION July 2001 FOURTH EDITION August 2005
WIND Visibility Weather Clouds VRB (3kt or less) - - - - VRB (less than 3kt) In speed more than 100 kt (P99) - Up to max. 3 phenomenas -
23
AERODROME FORECASTS - TAF
THE END
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