'Sleepless forecast' for Sydney to Hobart, with smoke haze and winds to play havoc with race

Uncertain weather conditions mean the bumper 157-strong fleet is preparing for a tough grind.

Black Jack leads the fleet through Sydney Heads during the start of the Sydney to Hobart Yacht 2018 race. Source: AAP

Crews are bracing for some of the most challenging Sydney to Hobart conditions in years after the Bureau of Meteorology delivered a "sleepless forecast" for next week's race.

Officials say they have contingency plans in place to combat Sydney's smoky haze while uncertain winds have skippers tipping one of the more unpredictable races for the 75th staging of the ocean classic.

After having to cancel this month's Big Boat Challenge due to extremely poor visibility, the Cruising Harbour Yacht Club on Friday welcomed the expected clear blue skies for the Boxing Day start.

But with Gabrielle Woodhouse from the Bureau of Meteorology unable to pinpoint when a southerly change would follow the north or north-easterly winds forecast for Boxing Day, the bumper 157-strong fleet were preparing for a tough grind.

"It's a sleepless forecast,' said Adrienne Cahalan, skipper of the 62-footer Chinese Whisper.

"Navigators are going to be up all night. It's going to be a very tactical race.

"This looks like a busy, busy race, this one - but a good one because it's always nice to know when it's all not set in stone because there's still lots of uncertainty.

"It's going to be hard to say which size boat the (overall) race winner is going to come out of as we sit here today."

While the super-maxis have traditionally dominated the race, Andrew Buckingham, skipper of 32-footer TSA Management, said the unusual forecast offered "some belief that it gives the little boats a chance" to claim handicap honours.

CHYC commodore Paul Billingham was confident the club wouldn't have to activate their contingency plans because of the bushfire-driven haze.

Firefight douse a home lost to a bushfire on Hassall Road in Buxton, New South Wales. Source: AAP

"It's obviously a difficult time here in NSW with fire surrounding Sydney and more to come tomorrow so our thoughts as a club and a race are with the firefighters," Billingham said.

"There's a lot more uncertainty this year than perhaps there has been in the past so we'll keep a weather eye on what's happening and make our decisions as the week goes by."

Infotrack skipper Bradshaw Kellett said he didn't anticipate any boats threatening LDV Comanche's 2017 race record of one day, nine hours, 15 minutes and 24 seconds.