WMO PUBLICATION No. 306 - MANUAL ON CODES
Several international code forms, in particular those needed for the functioning of basic systems in meteorology, contain provisions for regional or national options in the use of certain figure groups or the specification of certain symbolic letters. Volume II of the Manual on Codes contains information on the use made by regional associations and individual Meteorological Services of these options. It also contains full descriptions of additional code forms adopted by regional associations for use within the Region and inventories of those national code forms which might be of interest to other countries.
Publication details: https://community.wmo.int/activity-areas/wis/wis-manuals