The Seatrack Web (STW) oil drift calculation system is the official HELCOM drift model/forecasting and hindcasting system which is used for calculating the fate of oil spills. It is available online for national authorities and certain research organisations.
STW has an important role in the response cooperation in the Baltic Sea region and is since the 1990s used by all Baltic Sea coastal states -in some cases in parallel with national systems.
STW started as a simple trajectory model developed in the 1970s by Sweden. By 1990s it had evolved to an operational oil drift forecasting system. The HELCOM Recommendation 12/6 (superseded by Recommendation 24/7), stating that every country around the Baltic Sea should have an operational oil drift forecasting system by 1993, enhanced the development further.
The system has been, and continues to be, developed by Sweden in close cooperation with the users and the number of functions has increased over the years. STW is today hosted by the Swedish Meteorological and Hydrological Institute (SMHI) and developed together by SMHI and a group of partner institutions around the Baltic Sea Denmark (FCOO), Germany (BSH) and Finland (FMI).
A completely overhauled version, with new web interface and enhanced model algorithms, was released in 2014.
Predicting the fate of oil slicks
The STW system is able to make forecasts of how a cloud of particles (e.g. oil) will be moving and behaving on the sea surface. In case an oil spill is detected, the system is used to predict where the oil will be after some hours. This enables combatting units to be able to plan where to be positioned to make the most use of their oil recovery equipment. On shore, cleaning units can plan where to move their units so they can protect the shorelines most probable of being affected by the oil.
Identifying illegal polluters
If it is an illegal spill it is of interest to identify the polluter. STW combines modeling run in a backtracking mode with the HELCOM AIS data in order to identify which ships have passed the track of the oil spill. This information is used to find possible polluters for further investigations.