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Cloud-cover symbols used on weather teleprinters and aviation reports in the US [6] In the early 20th century, it was common for weather maps to be hand drawn. The symbols for cloud cover on these maps, like the modern symbols, were drawn inside the circle marking the position of the weather station making the measurements.
SIGMET, [1] or Significant Meteorological Information (AIM 7-1-6), [2] is a severe weather advisory that contains meteorological information concerning the safety of all aircraft. Compared to AIRMETs, SIGMETs cover more severe weather. Today, according to the advancement of technology in civil aviation, the SIGMET is sent as IWXXM model. [3]
In aviation, ceiling is a measurement of the height of the base of the lowest clouds (not to be confused with cloud base which has a specific definition) that cover more than half of the sky (more than 4 oktas) relative to the ground.
ICAO Meteorological Information Exchange Model (IWXXM) is a format for reporting weather information in XML/GML.IWXXM includes XML/GML-based representations for products standardized in International Civil Aviation Organization (ICAO) Annex III, such as METAR/SPECI, TAF, SIGMET, AIRMET, Tropical Cyclone Advisory (TCA), Volcanic Ash Advisory (VAA), [1] Space Weather Advisory and World Area ...
The laser is pointed upward, and the time required for reflected light to return to the station allows for the calculation of the height of the cloud base. Because of the limited coverage area (the laser can only detect clouds directly overhead), the system computer calculates a time-averaged cloud cover and ceiling, which is reported to ...
WXXM 1.0 was introduced in 2007, representing METAR, SPECI, TAF, SIGMET and other ICAO information as specified in International Civil Aviation Organization (ICAO) Annex III. WXXM 1.1 [1] was released in 2010 with a number of additional products beyond ICAO Annex 3. WXXM 2.0 was released in 2014 as a major update.
VFR / VMC visibility requirements in the US. In aviation, visual meteorological conditions (VMC) is an aviation flight category in which visual flight rules (VFR) flight is permitted—that is, conditions in which pilots have sufficient visibility to fly the aircraft maintaining visual separation from terrain and other aircraft.
A World Area Forecast Centre (WAFC) is a meteorological centre that provides real-time meteorological information broadcasts for aviation purposes. These broadcasts are supervised by International Civil Aviation Organization (ICAO) in order to fulfill requirements of the ICAO Annex 3 covering meteorological information which is necessary for flights.