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The METAR format was introduced internationally on 1 January 1968, and has been modified a number of times since. North American countries continued to use a Surface Aviation Observation (SAO) for current weather conditions until 1 June 1996, when this report was replaced with an approved variant of the METAR agreed upon in a 1989 Geneva agreement.
The Citizen Weather Observer Program is a program to collect surface weather observations from thousands of privately operated weather stations, into the FindU database, and forward it to the Meteorological Assimilation Data Ingest System (MADIS Archived 2009-03-12 at the Wayback Machine), operated by the National Oceanic and Atmospheric Administration (NOAA).
The airport observations are then transmitted worldwide using the METAR observing code. METAR reports typically come from airports or permanent weather observation stations. Reports are generated once an hour; however, if conditions change significantly, they may be updated in special reports called SPECIs. [9] [10] [11] [12]
The present weather symbol depicts the current weather which normally is obstructing the visibility at the time of observation. The visibility itself is shown as a number, in statute miles in the United States and meters elsewhere, describing how far the observer can see at that time. This number is located to the left of the present weather ...
This is a code number from 0 to 4, with 0, 1 and 2 meaning data is included, and 3 and 4 indicating no precipitation data. i X is a code number indicating the manner of station operation, and the format used in group 7wwWW; codes 1, 2 and 3 indicate a staffed station, while codes 4 to 7 indicate an automatic station.
051730Z indicates that the report was issued on the 5th of the month at 1730 UTC (also known as Zulu, hence the Z). 0518/0624 indicates that the report is valid from the 5th at 1800 UTC until the 6th at 2400 UTC. The remainder of the first line contain the initial forecast conditions. Variations of the codes used for various weather conditions ...
A TTF is a professionally considered forecast for weather over a two-hour period, [1] and is based on an actual weather report, such as a METAR or SPECI and appended to the end of it. [1] A TTF is similar to or sometimes in addition to a TAF, a terminal aerodrome forecast, but during the TTF's validity period is considered superior to a TAF.
Airport observations can be transmitted worldwide through the use of the METAR observing code. Personal weather stations taking automated observations can transmit their data to the United States mesonet through the use of the Citizen Weather Observer Program (CWOP), or internationally through the Weather Underground Internet site. [ 7 ]