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Aviation Weather Observation and Reports

  1. What is the difference between meteorological observation and report?
  2. What is SYNOP?
  3. What is METAR?
  4. What is SPECI?
  5. How are METAR/SPECI and SYNOP reports exchanged internationally?

  6.  
    Written by: CHEUNG Ping      June 2012


    As the designated meteorological authority in Hong Kong, the Hong Kong Observatory provides the weather services for international air navigation in accordance with the standards and requirements of the International Civil Aviation Organization (ICAO) and the World Meteorological Organization (WMO).

    The aviation weather observation and reports are made round-the-clock by the weather observer at the Airport Meteorological Office located inside the Control Tower of the Hong Kong International Airport.  Since April 2000, the station of synoptic weather observation for international exchange has been relocated from the Hong Kong Observatory Headquarters in Tsim Sha Tsui to the Hong Kong International Airport at Chek Lap Kok.  The weather observer at AMO is now responsible for issuing weather reports to the aviation community as well as to the meteorological community.


  1. What is the difference between meteorological observation and report?


  2. Meteorological observation is the evaluation of one or more meteorological elements, while a meteorological report is a statement of observed meteorological conditions related to a specified time and location.


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  3. What is SYNOP?


  4. Synoptic weather observation is a surface meteorological observation made at internationally agreed standard times, e.g. 00, 06, 12, 18 UTC (HKT = UTC + 8 hours).  The meteorological elements observed at a particular location and time are encoded in agreed formats of a meteorological report called SYNOP for the exchange among countries of the world at periodic times such as 3-hourly and 6-hourly.  The data are used for weather forecasting or climatological studies.


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  5. What is METAR?


  6. METAR is an aviation routine weather report issued at hourly or half-hourly intervals. It is a description of the meteorological elements observed at an airport at a specific time.  The elements include surface wind, visibility, runway visual range, present weather, clouds of operational significance, air temperature, dew-point temperature and atmospheric pressure.

    The aviation weather report also includes a section containing the trend forecast, which indicates the expected change in meteorological conditions in the next two hours.


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  7. What is SPECI?


  8. SPECI is aviation special weather report issued when there is significant deterioration or improvement in airport weather conditions, such as significant changes of surface winds, visibility, cloud base height and occurrence of severe weather. The format of the SPECI report is similar to that of the METAR and the elements used have the same meaning. The identifier METAR or SPECI at the beginning of the weather report differentiates them.


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  9. How are METAR/SPECI and SYNOP reports exchanged internationally?


  10. METAR/SPECI are exchanged internationally through the Aeronautical Fixed Telecommunication Network (AFTN).  This aging system is gradually being replaced by the Aeronautical Message Handling System (AMHS) which supports higher bandwidth and the transmission of binary data.  As for the data format, the aviation community is also moving from alpha-numeric to XML which is more friendly to automatic systems and support future data-centric operation of aviation users.

    SYNOP reports are exchanged internationally via the WMOs Global Telecommunication System (GTS).  The times of observations, the format of data and messages, the schedule of exchange and the responsibility of the reporting station are coordinated in the system.  To enhance regional and global connectivity and information management, the WMO Information System (WIS) is being built upon the GTS and will be the core information system in the future.  It makes use of dedicated telecommunication means such as data networks and satellite-based telecommunications to ensure service quality, as well as the Internet to enable flexible data delivery service.  As for the data format, table-driven code form will still be used for the exchange of SYNOP reports.


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Last revision date: <27 Dec 2012>