World Meteorological Organization

The Manual on the Global Telecommunication System (WMO-No. 386) was published by WMO to facilitate cooperation in respect of meteorological telecommunication between WMO Members and specify obligations in the implementation of the World Weather Watch Global Telecommunication System (GTS). It provided detailed guidelines for practices and procedures, including abbreviated headers and related specifications, used by the International Civil Aviation Organization (ICAO) for exchanging aeronautical meteorological data through its Aeronautical Fixed Service (AFS). 

However, according to the WIS 2.0 implementation plan, the Global Telecommunication System (GTS) will be decommissioned by 2033, and National Meteorological and Hydrological Services will use the WIS 2.0 platform for data exchange instead. 

In 2024, at the seventy-eighth session of the WMO Executive Council, Resolution 16 (EC-78) stated that "...the Manual on the Global Telecommunication System (WMO-No.386) will no longer be updated from 31 December 2024” and also requested WMO “…​to liaise with ICAO in respect of an extant requirement for Attachment II-5. Data designators T1T2A1A2ii in abbreviated headings of the Manual on the Global Telecommunication System.” 

Consequently, WMO's Infrastructure Department has created a webpage here to ensure the exchange of aeronautical meteorological data over the ICAO AFS is not affected by the freezing and subsequent deprecation of WMO-No. 386 and WMO-No. 9 Volume C1. 

https://community.wmo.int/en/activity-areas/wis/iwxxm/ahl-icao-data

Requests for additions or revisions to the abbreviated headings will be managed by the WMO Task Team on Aviation Data (TT-AvData) of the Infrastructure Commission (INFCOM) based on ICAO requirements. 

Further assistance or questions for clarification can be sent to TT-AvData via email.