World Meteorological Organization

Migration to Table-driven Code Forms (TDCF)

     The Fourteenth WMO Congress (Cg-XIV), held in 2003, supported the conclusions of the Commission for Basic Systems (CBS-XIII) that the Table-driven Code Forms (TDCF) are the solution to satisfy the demands of rapidly evolving science and technology, in view of their self-description, flexibility and expandability.

     Both Table-driven Code Forms: FM94-BUFR and FM95-CREX, offer great advantages in comparison with the Traditional Alphanumeric Codes (TAC) such as FM12-SYNOP and FM35-TEMP. The reliability of binary data transmission (BUFR) provides for an increase in data quality/quantity received at meteorological centres, which would lead to the generation of better products.

     Cg-XIV noted also with satisfaction that CBS had developed a thorough plan for a WMO-wide Migration to Table-driven Code Forms. The goal of the plan was the replacement of TAC for observational data exchange by the binary code BUFR. Cg-XIV noted that the plan was ensuring a smooth transition without negative impacts on the World Weather Watch operations. The basic principles of the plan were:

a.   The migration process was flexible. Within the target dates defined in the plan (spanning from 2005 to 2015 depending on the data type), WMO Members could choose their own timetable for the migration. It was the data producer, not the user, who was the initiator of the migration process;

b.   The use of CREX was an interim step in the migration to BUFR;

c.   Data users must have access to new data produced in BUFR or CREX and be able to receive data exchanged in BUFR or CREX; data users should have first priority for training; data users should implement BUFR and CREX decoders as soon as possible; dual transmission (initially in BUFR and TAC, later in BUFR and CREX) should be provided, where data users were unable to receive or process BUFR or CREX;

     Cg-XIV was pleased that ECMWF and some WMO Members would make software for encoding/ decoding BUFR/CREX available free of charge for WMO Members and with limited remote assistance. It also noted that some other WMO Members would make their encoding/ decoding software available at request. Cg-XIV recognized that the costs involved in the implementation of the Migration Plan should be compensated by the benefits to be gained, noting that the Migration Plan allowed sufficient time and flexibility for implementation.

     Cg-XIV endorsed the Migration Plan developed by CBS and urged every WMO Member country to develop as soon as possible a National Migration Plan, derived from the International Plan, with analysis of impacts, costs, solutions, sources of funding (as necessary), national training, technical planning and schedule.