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22.12.2016 23:02 Age: 360 days
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IMOS OceanCurrent predicts speed for Sydney to Hobart yacht race

Ocean currents (on present indications) are favourable for a quick race, especially at first, when a tail current associated with a large anti-clockwise (warm-core) eddy off Sydney will add a few knots to the fleet's speed over the ground.

Map showing a small clockwise eddy south of Jervis Bay on (image: IMOS OceanCurrent 19 December)

Map showing the rhumbline cutting across a large but fairly weak clockwise eddy that is likely to persist until race day (image: IMOS OceanCurrent 21 December)

The challenge here will be deciding how far offshore it is best to go to optimise current as well as wind. The first image at right (click to expand) shows the cooler coastal temperatures that we often see under these conditions and associate with reduced southward speed (see map updates here). This eddy has been off Sydney since about 7 Dec and is quite likely to still be there on race day.

The first image at right also shows a small clockwise eddy south of Jervis Bay. This will either grow in place or be swept southwards in coming days. In either case, it will mean that inshore and offshore yachts may experience very different currents off southern NSW while also dealing with the southerly wind change presently forecast.

Currents east of Bass Strait do not appear to be particularly strong this year. The rhumbline (2nd image at right) presently cuts across a large but fairly weak clockwise eddy that is likely to persist until race day.

As in past years, anyone wishing to overlay the yachts' positions on our maps of ocean currents can do this using Google Earth.

We wish the competitors a safe but exciting race, and cross our fingers that our computers keep running unattended through our Christmas Shutdown. If our images stop updating, it probably means there has been a power interruption in Hobart.


This article, by David Griffin, originally appeared on the news page of IMOS OceanCurrent