What is a TAF in aviation weather?

A TAF (Terminal Aerodrome Forecast) is a standard format used in aviation to forecast meteorological conditions within a 5-statute-mile radius of an airport runway complex, typically covering a 24 or 30-hour period.

What does FM mean in a TAF?

FM (From) indicates a rapid and significant change in the meteorological conditions, occurring within less than an hour. All forecast parameters after this indicator completely replace the previous ones.

What is the difference between BECMG and TEMPO?

BECMG (Becoming) indicates a gradual transition of meteorological conditions over a period of 1 to 2 hours. TEMPO (Temporary) describes expected intermittent fluctuations that last for less than one hour in each instance and cover less than half of the specified time period.

Understanding TAF Reports

A TAF (Terminal Aerodrome Forecast) is a meteorological report that outlines forecasted weather parameters near a specific airport runway terminal area, vital for pre-flight planning and alternate routing selection.

Key Differences from METAR

While a METAR provides the observed, current weather conditions, a TAF presents structured predictions. TAF reports are compiled by professional meteorologists and are typically updated every 3 or 6 hours, providing coverage periods spanning 24 or 30 hours.

Understanding Weather Change Indicators

Because weather is dynamic, TAFs segment their forecasts using specific transition indicators:

FM (From): Indicates a rapid, permanent transition to new weather conditions occurring within less than an hour. All parameters following this code replace previous entries.
BECMG (Becoming): Describes a steady, gradual transition of meteorological conditions over a designated period (usually 1 to 2 hours).
TEMPO (Temporary): Indicates temporary fluctuations of weather conditions that are expected to persist for less than an hour at a time and cover less than 50% of the specified timeframe.
PROB30 / PROB40 (Probability): Indicates a 30% or 40% probability of occurrence for a specific meteorological hazard (such as thunderstorms, wind shear, or low visibility) during a specified window.

Practical Decoded Example


                    TAF LBSF 152300Z 1600/1700 24008KT 9999 FEW030 TEMPO 1604/1608 4000 BR BKN012 FM161200 32015G25KT SCT040

How to break this down:

LBSF: Forecast is for Sofia International Airport.
152300Z: Issued on the 15th day of the month at 23:00 UTC.
1600/1700: Forecast validity starts on the 16th at 00:00 UTC and ends on the 17th at 00:00 UTC.
24008KT 9999 FEW030: Initial baseline weather forecast of wind from 240° at 8 knots, visibility 10 km or more, and few clouds at 3000 feet.
TEMPO 1604/1608 4000 BR: Temporarily between 04:00 and 08:00 UTC on the 16th, visibility may drop to 4000m due to mist (BR) with broken clouds at 1200 feet.
FM161200 32015G25KT: From 12:00 UTC on the 16th onwards, weather rapidly changes to gusty northwest winds (320° at 15 knots, gusting to 25 knots) with scattered clouds at 4000 feet.