SYNOP is a numerical code
A code is a rule for converting a piece of information into another form or representation , not necessarily of the same type....

 (called FM-12 by WMO
World Meteorological Organization
The World Meteorological Organization is an intergovernmental organization with a membership of 189 Member States and Territories. It originated from the International Meteorological Organization , which was founded in 1873...

) used for reporting weather
Weather is the state of the atmosphere, to the degree that it is hot or cold, wet or dry, calm or stormy, clear or cloudy. Most weather phenomena occur in the troposphere, just below the stratosphere. Weather refers, generally, to day-to-day temperature and precipitation activity, whereas climate...

 observations made by manned and automated weather stations. SYNOP reports are typically sent every six hours on shortwave
Shortwave radio refers to the upper MF and all of the HF portion of the radio spectrum, between 1,800–30,000 kHz. Shortwave radio received its name because the wavelengths in this band are shorter than 200 m which marked the original upper limit of the medium frequency band first used...

 using RTTY
Radioteletype is a telecommunications system consisting originally of two or more electromechanical teleprinters in different locations, later superseded by personal computers running software to emulate teleprinters, connected by radio rather than a wired link.The term radioteletype is used to...

. A report consists of groups of numbers (and slashes
Slash (punctuation)
The slash is a sign used as a punctuation mark and for various other purposes. It is now often called a forward slash , and many other alternative names.-History:...

where data is not available) describing general weather information, such as the temperature, barometric pressure and visibility at a weather station.

Message format

This is the general structure of a SYNOP message. Numbers shown here are fixed (group indicators), numbers replacing the x's contain the weather data plus information about the station's position (and speed and direction where applicable).

xxxxx xxxxx 99xxx xxxxx xxxxx xxxxx 00xxx 1xxxx 2xxxx 3xxxx 4xxxx 5xxxx
6xxxx 7xxxx 8xxxx 9xxxx 222xx 0xxxx 1xxxx 2xxxx 3xxxx 4xxxx 5xxxx 6xxxx
70xxx 8xxxx
333 0xxxx 1xxxx 2xxxx 3xxxx 4xxxx 5xxxx xxxxx 6xxxx 7xxxx 8xxxx 9xxxx

External links

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