Every Boxing Day, hundreds of sailors set off in the famous Rolex Sydney Hobart Yacht Race.
The race course from Sydney to Hobart is along the extension of the East Australian Current (EAC). The old racing trick was to sail southeast from Sydney and take the temperature of a bucket of seawater every hour or so.
If the temperature suddenly increased, sailors knew they had reached the EAC and turned south. They’d aim to ride this current all the way to Hobart.
However, oceanographers know that the EAC between Sydney and Hobart is not a straight conveyor belt. It involves a chaotic eddy field.
The optimal course is a skilful balance of present and future conditions along with the expected speed of the boat.
To find the present location of the eddies, sailors can use satellite information. These images show today’s temperature information over a much larger area than a thermometer in a bucket.
Savvy sailors can go one step further. They can consider the future wind and ocean conditions using output from numerical ocean forecasting models.
Ocean forecasts are provided by the Australian Bureau of Meteorology (BOM) using the Ocean Modelling Analysis and Prediction System (OceanMAPS).
These are freely available on the BOM website. The forecasts are updated daily with a new analysis of available data and will differ from day to day.
The science underpinning OceanMAPS is developed by the Bluelink partnership.
The Bluelink partnership produces ocean forecasts and data that are widely used by the Australian community: mariners, researchers, fisheries, the Royal Australian Navy, and search and rescue authorities.
At this time of year, Bluelink ocean science also serves the navigators eyeing the Sydney to Hobart trophy.
The 2021 Rolex Sydney Hobart Yacht Race will start at 13:00 hrs (02:00 hrs UK) on Sunday 26 December.