TAF

TAF (Terminal Aerodrome Forecast) is a weather forecast specifically for airports, detailing expected meteorological conditions relevant to flight operations. It predicts changes in specific weather parameters over a defined forecast period, which may vary from 9, 12, 18, or 24 hours, depending on the airport. The TAF is updated at regular intervals to ensure accuracy.

The structure of a TAF follows similar coding to a METAR, using ICAO standard abbreviations.

Example TAF:

DAAG 041100Z 0412/0518 22020G35KT 9999 SCT040
TEMPO 0412/0416 22030G40KT SHRA BKN030CB
BECMG 0418/0420 22015G25KT
TEMPO 0510/0518 26020G35KT SHRA BKN030CB
PROB30 TEMPO 0512/0518 TSRA

Components of a TAF

Each TAF report consists of different sections:

Base Status

The initial conditions of the forecast, including:

• Surface wind (direction, speed, gusts if applicable)
• Horizontal visibility
• Significant weather phenomena
• Cloud cover and types

This section also includes:

• ICAO airport identifier (e.g., DAAG for Algiers Houari Boumediene)
• Report creation time (041100Z means 4th day of the month at 11:00 UTC)
• Forecast validity period (0412/0518 means valid from the 4th at 12:00 UTC to the 5th at 18:00 UTC)

The initial conditions in the TAF usually align with the latest METAR at the time of issuance.

Change Groups

TAFs contain specific codes indicating expected changes in weather conditions over time. Changes are only noted when they exceed certain predefined thresholds.

TEMPO (Temporary Changes)

• Indicates temporary fluctuations expected during the specified period.
• Each fluctuation lasts no longer than half of the given time range.
• Example:

  TEMPO 0412/0416 22030G40KT SHRA BKN030CB
  

  This means that between the 4th at 12:00 UTC and the 4th at 16:00 UTC, temporary rain showers (SHRA) and broken cumulonimbus clouds (BKN030CB) are expected, with wind gusts up to 40KT.

BECMG (Becoming)

• Indicates a gradual change in conditions starting at the first listed time and completed by the second.
• After this period, the new condition is considered the new base status.
• Example:

  BECMG 0418/0420 22015G25KT
  

  This means that between the 4th at 18:00 UTC and the 4th at 20:00 UTC, wind speeds will reduce to 15 knots with gusts of 25 knots.

PROB (Probability)

• Used only with TEMPO to indicate a 30% or 40% probability of temporary changes.
• Example:

  PROB30 TEMPO 0512/0518 TSRA
  

  This indicates a 30% probability of temporary thunderstorms with rain (TSRA) occurring between the 5th at 12:00 UTC and the 5th at 18:00 UTC.

FM (From)

• Indicates an abrupt change expected at a specific time.
• Example:

  FM1200 28015KT CAVOK
  

  This means that from 12:00 UTC onward, the wind will shift to 280° at 15KT, and conditions will be CAVOK (clear skies and good visibility).