A Terminal Aerodrome Forecast (TAF) is a concise weather prediction for a specific airport and its immediate surrounding area, typically within a five-statute-mile radius. This forecast provides essential meteorological information that enables safe and efficient flight operations, covering expected conditions like wind, visibility, cloud cover, and various weather phenomena.
Scheduled Issuance
Terminal Aerodrome Forecasts are issued routinely on a predetermined schedule, typically four times daily, every six hours. Standard issuance times are 0000, 0600, 1200, and 1800 Coordinated Universal Time (UTC). All aviation weather reports use UTC, also known as “Zulu” time, to maintain a global standard. Forecasters usually prepare and file these routine TAFs 20 to 40 minutes prior to their scheduled release times.
Unscheduled Updates
Beyond the regular schedule, TAFs can be amended at any time if significant changes in weather conditions occur or are anticipated. These unscheduled updates, known as TAF amendments, are issued when the current forecast no longer accurately represents the expected weather. Forecasters continually monitor conditions to maintain accuracy.
Specific criteria trigger these amendments. For instance, a TAF is amended if the actual mean wind direction differs from the forecast by 30 degrees or more, especially with a mean wind speed of 13 knots or greater. Similarly, an amendment is warranted if the forecast mean wind speed changes by 10 knots or more, with an original or newly expected mean wind speed of 12 knots or greater.
Significant changes in visibility also prompt amendments, such as when it falls below or increases to specific thresholds like 5, 3, 2, 1, or ½ statute miles. The occurrence or non-occurrence of forecasted thunderstorms, freezing rain, freezing drizzle, or ice pellets necessitates an amendment, as do changes in their intensity. Amendments are also issued for changes in ceiling, particularly if it drops below or rises above specific altitudes like 3000, 2000, 1000, 600, or 200 feet.
Forecast Validity
Each TAF covers a specific duration, known as its validity period. Most TAFs are valid for either a 24-hour or a 30-hour period, indicating the duration for which the forecast meteorological conditions apply. For example, a TAF issued at 0000 UTC might be valid until 0000 UTC the following day for a 24-hour forecast. An amended TAF may have a shorter validity period compared to a routine forecast.
Why Timing Matters for Users
The timely issuance and updating of TAFs are paramount for their primary users, including pilots, airline dispatchers, and air traffic controllers. These aviation professionals rely on current and accurate weather information for effective planning and informed decision-making. Access to the latest TAF ensures flight routes, fuel requirements, and alternate airport selections are based on the most up-to-date weather outlook. This data is fundamental to maintaining safety and efficiency across all phases of flight.