This section explains how to represent the WIGOS station identifier in WMO standard code forms.

Reducing ambiguity through systematic use of WIGOS station identifiers

An observing facility may have several WIGOS station identifiers. Using OSCAR, it is possible to discover all the WIGOS station identifiers associated with that facility. In theory, this allows any of the possible WIGOS identifiers to be used in a report of an observation, but in practice, doing so would result in a lot of additional work for all users of the observation. A disciplined approach to using WIGOS station identifiers in a report will reduce the work for end-users.

Choosing which WIGOS station identifier to use

The following practices will make it easier for users of observation reports to link observations from a single observing facility:

1. Use the same WIGOS identifier for all reports of the same type from that observing facility. For example, always use the same identifier for surface synoptic reports;
2. If there is one, use the WMO Programme station identifier that is associated with the type of observation being reported to derive the WIGOS station identifier. For example, a WIGOS station identifier associated with the World Weather Watch land-station identifier would be used for surface synoptic reports;
3. There is no requirement to introduce new WIGOS station identifiers if the observing facility already has one. For example, whatever type of observation is reported, if the facility has a WIGOS identifier derived from a World Weather Watch station identifier, then that WIGOS identifier may be used for reporting any type of observation. However, following practice (a) above, different types of reports might use different pre-existing identifiers.

Messages containing only reports from stations that have a pre-existing station identifier for the type of report being exchanged

In many cases, such as for surface observations from World Weather Watch land stations that existed before the introduction of WIGOS station identifiers, no change is needed to report from those stations in BUFR or CREX. The existing identifier should be reported as in the past.

Nevertheless, it is good practice also to report the derived WIGOS station identifier.

Messages containing reports from stations that do not have a pre-existing station identifier for the type of report being exchanged

New observing facilities, or those reporting new types of observations, will need to report the full WIGOS station identifier. BUFR and CREX messages that include reports from stations that do not have a pre-existing station identifier appropriate to that type of report have to include the BUFR/CREX sequence 3 01 150 to represent the WIGOS station identifier.

If there is no pre-existing identifier, the value for the station identifier in the standard BUFR/CREX sequence should be set to the value representing "missing".

Reporting the WIGOS station identifier in a BUFR/CREX message

When constructing a BUFR or CREX message that refers to WIGOS station identifiers, the sequence 3 01 150 must appear in the message before the sequence describing the information from those stations.
That is, the message contents should be in the order:
< sequence for the WIGOS station identifier (3 01 150)>
< sequence for the data being reported>

Reporting the WIGOS station identifier when the reporting environment can only handle traditional alphanumeric codes

Traditional alphanumeric code forms cannot represent WIGOS station identifiers. Furthermore, observations can only be exchanged in traditional alphanumeric code if the observing facility has been allocated a conventional World Weather Watch station identifier. Observation facilities that have not been allocated a World Weather Watch station identifier must exchange their observations using the Table Driven Code Forms.

In some circumstances, however, it may be necessary to report observations internationally from stations that do not have a pre-existing World Weather Watch station identifier and for which the technical environment only supports the traditional alphanumeric codes.

The recommended approach in this case is to agree on a national practice that meets the local technical constraints to identify the observing station in reports (or a bilateral practice where an arrangement is made to translate traditional alphanumeric code to Table Driven Code Format for international exchange). These national reports must be converted to Table Driven Code Format before the international exchange; the conversion must include a translation from the method of identifying the station used in the national report to the WIGOS station identifier for that station. Extreme care must be taken to ensure that the national report is not distributed internationally.

Examples of a possible national practice for a surface synoptic report might be to use five alphabetic characters for the identifier, or a numeric identifier in the range 99000 to 99999 (only two identifiers in that range, 99020 and 99090, were recorded in Weather Reporting (WMO-No. 9), Volume A, in April 2016). A look-up table from that identifier to the WIGOS station identifier would allow the translating centre to insert the WIGOS station identifier.

The situation is more complex for upper-air reports. In this case,the WMO Secretariat should be asked for assistance.