SYNOP (surface synoptic observations) is a numerical code used for reporting weather observations made by manned and automated weather stations.

It isn't a Aeronautical Bulletin but is a Statistic Bulletin.
SYNOP reports are typically sent every six hours.
This Bulletin contain information about visibility, ceiling, clouds and pressure and AWOS systems are able to compile automatically.  

Synop 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



​

Example

 

AAXX 13064  16194  41660  80502 10235  20140  40086  57007  78082  8693/  333  20201  30020  82930  85635  





Code   Symbol                        Significance​

AAXX      MiMiMjMj                      SYNOP Bulletin
13064    YYGGIw                         day 13 at 06 UTC Wind is observed by anemometer (Iw=4)
16194     Iiiii                              On the Italian, Greek or Maltese station  (16) number 194
41660    IrIxhVV                         There are no data about precipitation because reading is not executed (Ir=4)        .                                              The station is manned by staff (not automatic) in the first section contains data                      .                                              about the present and past (Ix = 1) The base of low clouds is between 1000 and                                                       .                                              1500 meters (h=6 ) Minimum Visibility is 10 Km ( VV=60 )
80502    Nddff                           Sky coverage is 8/8 ( N=8 ) Wind direction = 50° Wind speed = 2 KN (ddff = 0502)
10235    1SnTTT                         Air Temperature = +23,5°C  
20140    2SnTdTdTd                   Dew Point = +14,0°C
            3PoPoPoPo                    Atmospheric Pressure = N.A.
40086   4PPPP                          QNH = 1008,6 hPa
57007    5appp                          The barometric trend is decreased and the pressure change in thelast three hours .                                              was 0.7 hPa
            6RRRtr                          Precipitation = N.A
78082   7wwW1W2                      Weather Condition : light rain ( -RA) and in the last three hours occurred showers .                                               (2= Not Significant Data )
8693/   8NhClCmCh                     Cloud Coverage : consists of 6/8 of low clouds type of cumulonimbus anvil with . .             .                                               presence of high and undetectable altocumulus clouds
333                                           Section number 3
20201   2SnTnTnTn                     Minimum Temperature was 20,1°C
32020   3ESnTgTg                       Ground Status = wet
82930   8NsChshs                       Other Clouds CB with coverage equal to 2/8
85635   8NsChshs                       Other Clouds : SC  with coverage equal to  6/8