using WMO Identifiers, which had the form of 5-digit numbers for synoptic and climate stations. Many countries ran out of numbers within their allowable ranges and were unable to register additional stations. The new WIGOS Station Identifiers (WSI) were created with a structure of 4 blocks, using digits and alphanumeric characters that allow essentially an unlimited number of stations to be registered. The 4 parts of WSI are identifier series - issuer - issue number - identifier. Existing WMO id's were migrated to the WSI format, eg "0-20000-0-72295" for LAX. "20000" is the issuer code for WMO itself, and countries use their 3-digit ISO code as issuer code A presentation at the WMO site explains: A critical component: WIGOS Station Identifiers Basic concept of the WIGOS Station Identifiers (WSIs): Many countries have run out of numbers within their allowable ranges and are thus not able to register additional stations Created to allow essentially an unlimited number of stations to be registered in WIGOS Its implementation by Members is mandatory, as part of the WIGOS Technical Regulations, including the WIGOS Metadata Standard WSIs should not have meaning in themselves: Users should not look for metadata in the patterns of a WSI, they should go to OSCAR/Surface for the metadata of the station associated with that WSI Assigning of WSIs (A) For “new stations” (those that started to operate or became affiliated with a WMO Program after 1 July 2016)–to develop and document their WSI national schemas, meaning: using the 3-digits ISO Country code in the Issuer of Identifier (2nd block) and defining the national rules for distributing the numbers in the 3rd and 4th blocks (Issue Number and Local Identifier) for the stations in their territory For stations registered in WMO-No.9 Volume A prior to July 2016: They have been migrated into OSCAR/Surface with their traditional 5-digits WMO identifiers being automatically converted into WSI: range 20000-20010 in 2nd block, “0” in 3rd block and the traditional WMO ID in 4th block. United States weather agency identifiers The National Weather Service uses several schemes for identifying stations. It typically relies on the ICAO and WMO identifiers, although several weather forecast offices (WFOs) and weather radar sites that have moved away from airports have been given their own codes which do not conflict with existing codes. These typically end in X, such as where Birmingham, Alabama (BHM) had its radar site replaced by