Sydney to Hobart 2013: Massive swell forecast Crews in the Sydney to Hobart yacht race have been warned to expect boat- and bone-bruising swells by the weekend, with waves reaching 10 metres in Bass Strait and 12 metres in southern Tasmania. While the maxi yachts in the 94-strong fleet can expect a smoother run south, the smaller boats are in for a far more challenging passage to Hobart, according to the Bureau of Meteorology's Andrew Treloar in his final weather briefing to sailors this morning. For the start, at 1pm, the forecast was for south to south-easterly winds of 10 to 15 knots outside the Heads - "maybe a little less in the harbour" - and a swell of one to two metres. A crew member makes final adjustments prior to the 2013 Sydney to Hobart yacht race. Lighter winds are forecast further south by Friday morning when a north-easterly picks up and strengthens by Saturday. The maxis should pass before the heavy weather, but from Saturday winds should increase from strong to gale force and seas will increase. Treloar said that from Saturday: "The winds running down the coast will start to get quite strong. We are looking at 15 to 20 knots up in the northern parts of the race course ... getting to 20 to 30 knots near Gabo Island. There will be a wind warning out for NSW waters ... and seas will be picking up according to wind strength increasing ... up to two to two-and-a-half metres and that easterly swell pushing in at about a metre or so. However, Treloar said the big change will come late Saturday evening. We are looking at gale-force winds, west to south-west of about 30 to 40 knots. They will probably come through with quite a thump too because you are going from the north to north-easter round to the west south-wester. The race leaders round the first mark. The seas with those winds will get up to three to four metres, that is the wind-driven wave. Initially when that change goes through, we will still have the remnants of that easterly swell. There won't be much westerly swell because we haven't enough time for that. The Wild Oats XI crew hard at work on deck as the fleet leaves Sydney Harbour. Conditions could be quite choppy and messy ... you will have the good sea wave from the wind. But on Sunday morning, said Treloar, winds should pick up to 35 to 45 knots, with gusts hitting at 40 to 60 knots "on top of the average wind." Treloar said a westerly swell should then build to about three metres. "That will be on top of that sea wave of three to four metres," he said. If you put those two wave trains together you will get a significant wave height of about five to six metres. We are looking at some pretty big waves, with the occasional big wave coming of about 10 metres or so. Treloar said that as the race heads to south-east Tasmania gale-force winds will continue with "probably pretty similar conditions with regards to sea and swell, if not maybe just a little bit higher down there." "Down to the south of Tasmania, south east, you are looking at about seven or more metres for a combined wave height ... treacherous conditions as far as the winds and the waves go," Treloar said. He added that by Monday the combined wave heights could be up to six metres "with a maximum wave height of about 10 to 12 metres."