Appendix 1: Additional information for aviation weather reports (METAR)
The airports produce two different kinds of weather reports: aviation weather reports (METAR) and weather observations. Aviation weather reports (METAR) are generally compiled from the data collected by the airport's various observation equipment in compliance with the regulations in ICAO Annex 3*. Weather observations refer to data collected by certain observation equipment at an airport. Due to different calculation methods and deduction chains, the differences between an aviation weather report (METAR) and a weather observation at an aerodrome can be quite large.
The Finnish Meteorological Institute has been appointed as the designated producer of aviation weather reports in the Finnish Flight Information Region until 31 January 2010 (Decision of the Finnish Ministry of Transport and Communications, 5 March 2013, record number LVM/1185/02/2012).
ICAO Annex 3* establishes specific formal and material requirements for METAR weather reports.
Applications containing aviation weather reports (METAR) should contain the following disclaimer: "METAR reports may be missing or available later than in the Aeronautical Fixed Telecommunication Network (AFTN)"*Annex 3 to the Convention on International Civil Aviation – Meteorological Service for International Service for International Air Navigation