Observation stations within the Ship SYNOP station network transmit their observations in the form of a Ship SYNOP message, also referred to as FM 13-IX SHIP message. Hourly measurements are taken worldwide from sea based stations (ships, rigs, platforms and moored buoys) , and the report is transmitted at 6-hourly intervals at the standard hours of observation which are: 0000, 0600, 1200, and 1800 UTC. The Ship SYNOP message contains observed elements such as weather, cloud, temperature, precipitation, wind, visibility, and pressure.

In order for a Ship SYNOP message to be transmitted by an observation station, specific instruments are required to perform to certain standards. These include an anemometer, thermometer, station observer, visiometer, barometer, hygrometer, and raingauge.