The WMO FM-94 BUFR, Binary Universal Form for the Representation of Meteorological data, is a binary code designed to represent, employing a continuous binary stream, any meteorological data. It has been designed to achieve efficient exchange and storage of meteorological and oceanographic data. It is self defining, table driven and very flexible data representation system, especially for huge volumes of data.
ECMWF provide BUFR User's Guide (pdf) and BUFR Reference Manual (pdf) that describes latest BUFR tables and ECMWF observation types and subtypes. For each subtype there is a template describing the observation.
The first version of ECMWF BUFRDC software was designed and implemented in 1987. A great deal of experience has been gathered in handling binary coded observations since then.