American super-yacht Comanche was leading the fleet in Australia's Sydney to Hobart on Saturday, after bolting out of the harbour at the start of the gruelling 628-nautical-mile (1,163 kilometre)race.

Australian rival and 2014 line honours winner Wild Oats XI had initially led in the moments after the starter's horn blew, but was overtaken by supermaxi Perpetual Loyal before Comanche took the lead.

Officials have warned of thunderstorms and gales later Saturday as the fleet travel down the east coast of Australia, saying those at the back of the pack will see the worst of the weather.

"For the leading boats, the further south they can get the better," Michael Logan from the Bureau of Meteorology said.

"But for the back boats that looks like where the gales are and where the change will pack its strongest punch. And the boats furthest south will get the moderating breeze first."

Three yachts were early retirements, including one which was withdrawn after a collision in Sydney Harbour, bringing the fleet down to 105 boats.
Ark323 was one of two Chinese entries and one of 27 foreign boats in the race which draws spectators on land and in boats in Sydney on Boxing Day.

"Ark323, one of two Chinese entries, retired following a collision 300 metres after the start. All on board were safe," race organisers said in a statement.

Australian boat Cougar II retired at about the same time with damage to her starboard quarter while the British entry Lupa of London retired with unspecified damage.

Forecasters expect north-easterly winds to strengthen to 20 knots or 30 knots during Saturday evening, with thunderstorms and some gusts reaching well over 30 knots.

The strength and duration of the southerly winds is expected to be crucial in determining the winner of the race organised by the Cruising Yacht Club of Australia.

The winds are expected to ease on Sunday, and will be light off the coast of Tasmania as the boats head to Hobart's Constitution Dock.

"The maxis could get away from us in the light winds, but every corner has a chance this year," said Roger Hickman, skipper of Wild Rose which won the race on handicap last year.

Storms are part and parcel of the race, with six men dying, five boats sinking and 55 sailors rescued on a fatal night in 1998 when a deep depression exploded over the fleet in the treacherous Bass Strait.

Wild Oats holds the race record of one day, 18 hours, 23 minutes and 12 seconds set in 2012.
Source: AFP