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To address the current difference between Australian TAF and METAR/SPECI boundaries, it is proposed that the Bureau aligns the TAF boundary with the METAR and ICAO practices.
The Bureau recommends that:
This change would allow the Bureau to align TAF and METAR/SPECI boundaries to ICAO requirements, as noted in ICAO Annex 3 and Document 8896 Manual of Aeronautical Meteorological Practice.
Implementing this change will allow the Bureau to conform with requirements set in ICAO Doc 8896.
The Bureau is currently seeking feedback on this proposed change. Submissions will be reviewed in January 2023.
Concerns around inconsistencies in boundaries between the TAF and METAR/SPECI have been raised with the Bureau. ICAO states that weather phenomena included in TAFs are for the area at the aerodrome, i.e., the area within a radius of approximately 8 km of the Aerodrome Reference Point (ARP). The word “approximately” is used to cater for aerodromes that have perimeters which are not precisely a radius of 8 km from the ARP.
In Australia, the TAF "is a statement of meteorological conditions expected for a specific period in the airspace within a radius of 5 n mile of the ARP”. It's likely 5 n mile was chosen as it is based on the aircraft using Distance Measuring Equipment (DME) which measures in n mile and was historically used in most of ICAO Standards and Recommended Practices (SARPs) and associated guidance material.
The Bureau provides observations at aerodromes and disseminates these as METAR/SPECI. METAR/SPECI provide users with information on actual meteorological conditions and are one of the many sources of observations that support the TAF issuance and amendment service.
Meteorological equipment that enables the provision of METAR/SPECI are sited in accordance with ICAO and the present weather information is intended to be representative of conditions at the aerodrome (i.e., within a radius of approximately 8 km from the ARP) and, for certain specified present weather phenomena, in its vicinity, i.e., the area that lies within a radius of approximately 8 km and 16 km of the aerodrome reference point.
In Australia distances for METAR/SPECI are with respect to the Automatic Weather Station location, not the ARP. The Bureau recommends that the TAF boundary be modified from 5 n mile to 8 km, to align with METAR and ICAO practices.
The Bureau is currently seeking feedback on this proposed change, from all users of the TAF. If supported, the Bureau will plan the implementation of the necessary changes, including documentation updates, user education and training.