Aviation Metereology
As a pilot you always need to know in what weather conditions you will be flying.
The International Civil Aviation Organization (ICAO) has devised a system to record and report weather conditions to pilots, in a highly standarised format, which allows it to be understood throughout most of the world.
METAR is the format for reporting weather information. A METAR weather report is predominantly used by pilots and by meteorologists, who use aggregated METAR information to assist in weather forecasting.
Origination
METAR reports typically come from airport or permanent weather observation stations. Reports are generated at different intervals, typically once an hour, or when conditions change significantly.
Some reports are encoded by automated airport weather stations, located at airports, military bases, and other sites.
Some locations still use augmented observations, which are recorded by digital sensors, encoded via software, and then reviewed by certified weather observers or forecasters prior to being transmitted. Observations may also be taken by trained observers or forecasters who manually observe and encode their observations prior to transmission.
History
The METAR format was introduced 1 January 1968 internationally and has been modified a number of times since.
The World Meteorological Organization (WMO) keeps record of the base METAR code as adopted by the WMO member countries. (publication No. 782 "Aerodrome Reports and Forecasts")
Naming
The name METAR is commonly believed to have its origins in the French phrase “message d’observation météorologique pour l’aviation régulière”
The United States Federal Aviation Administration (FAA) lays down the definition as “aviation routine weather report” while the international authority for the code form, the WMO, holds the definition to be “aerodrome routine meteorological report.”
METAR is also known as Meteorological Terminal Aviation Routine Weather Report or Meteorological Aviation Report.