Black skies hang over the 2013 Rolex Sydney Hobart fleet ahead of the race start
Weather forecaster Andrew Treloar, presented a grim picture to skippers at the final briefing for the 2013 Rolex Sydney Hobart Race.
A front which is expected to hit the fleet on Saturday night will bring head winds winds gusting to 60kts and with seas of 7 metres and more off the Tasmanian coast.
Conditions at the start are expected to be 10-15kts, with a low pressure are moving away quite quickly.
Andrew Treloar conducting an earlier weather briefing for the 2013 Rolex Sydney Hobart Race
At 11.00am today the low pressure system is morning away from the coast of NSW, with a High in the Australian Bight, and a series of fronts coming through just to the south of Western Australia.
Tonight that weather pattern continues, with the low moving further away, the High and fronts all advancing towards Tasmania.
At 11.00am on Friday as the boats make their way down the coast. The boats will encounter a north easterly stream which will freshen up during the day. And by the evening could be fresh to strong. The first front from Western Australia will slip down to the south of Tasmania.
Friday evening a second front approaches to the south of the Australian Bight. A good northeasterly wind stream continues.
At 11.00am Saturday the main feature is the front moving up from the Bight. The boats are expected still to be on the NSW coast in a fresh NE breeze. Forecasters have the front to the west of Bass Strait at 11.00am on Saturday. By 11.00pm, 12 hours later the front will have moved into Bass Strait. The front is expected to hit boats in that area on Saturday evening.
Forecasters state that there is quite a vigorous flow behind the front, with winds of at least gale force predicted. A low pressure centre to the south of Tasmania will bring up SW gales as well.
Strong to gale force winds will continue around Tasmania through Sunday.
Conditions will ease in Bass Strait on Monday, with strong to gale force winds around Tasmania.
At race start, temperatures of 26 degrees are expected, with a S-SSE breeze of 10-15kts and seas of 1-2 metres, with an easterly swell of less than a metre.
These conditions are expected to continue for the first night of the race.
On Friday as the fleet moves from the SE to NE flow, winds may lighten, offshore there may be a little more breeze as the boats transition from the SE to NE flow. On Friday night the NE starts to freshen and swings to the North 10-15kts and seas about 1-2metres.
The swell of 1 metre will start to pick up.
On Saturday, winds running down the NSW coast will get reasonably strong with winds of 20-30kts around Gabo Island and Green Cape at the entrance to Bass Strait.
A strong wind warning for NSW waters is expected to be issued about that time with the seas increasing with the increase in wind strength.
The big change comes through Saturday evening, with the change expected by 11.00pm, and 6.00pm to 9.00pm around Green Cape.
A gale force W-SW wind of 30-40kts is expected. Due to the rapidity of the change there is expected to be a big initial thump from the change. A Gale Warning will be issued for that change later today or early tomorrow (Friday).
Sea are expected to be 3-4 metres for the wind driven wave, due to the remnants of the easterly swell coming through, there will be opposing seas initially.
Isobar and wind map - Bass Strait area 0800 Sunday December 29, 2013 - showing a low to the SE of Tasmanian and funnelling winds though Bass Strait
On Sunday winds are expected to be 35-45kts, with an average speed of 30-40kts and gusts of up to 60kts possible. The westerly swell will build to 3-4 metres or more, coupled with swells a total wave height of five metres is expected, with the occasional big wave of 10 metres or so.
In SE Tasmania, there are expected to be SW gales and similar sea conditions.
Conditions were described as 'treacherous' by the forecast officials.
For the next few days conditions are expected to moderate but still stay around gale force with waves of 10-12 metres.
In terms of the tides and current, waves moving through Bass Strait will be opposing the current, and running at 2-3kts offshore.
Race Chairman Andrew Fox said that the navy have two helicopters on standby and are capable of winching at day or night, and they will effect night rescues if required.
Wind maps from www.predictwind.com showing the front advancing onto the SE Australian coast late Saturday night and early Sunday morning, and overcoming the incumbent Northerly wind
Colour coded wind scale - Yellow is 15kts average to Black at 50kts average - 2013 Rolex Sydney Hobart Race - Predictwind
2300hrs on Saturday with the Northerly still fresh and no sign of the advancing front - 2013 Rolex Sydney Hobart Race - Predictwind
0200hrs on Sunday as the Northerly is confronted by the advancing SW gale - 2013 Rolex Sydney Hobart Race - Predictwind
0500hrs on Sunday - with the change firmly in place - 2013 Rolex Sydney Hobart Race - Predictwind