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#246262 - 16/12/2004 17:23 Sydney Hobart race
squared Offline
Junior Member

Registered: 16/12/2004
Posts: 3
Loc: Sydney
Any of you gurus willing to have a stab at the conditions for the 26-30th yet?
:wave:
DD

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#246263 - 16/12/2004 17:31 Re: Sydney Hobart race
Craig Arthur Offline
Wind hazard researcher

Registered: 08/05/2001
Posts: 3549
Loc: 149.152009°E 35.187056°...
Hi squared,

As yet, I'm not willing to attempt an indepth forecast, as the race is still a long way off. Certainly closer to the date I'll put up a fairly detailed forecast of my expectations (probably on Christmas Eve with a chance I'll update on Christmas Day or early Boxing Day, depends if my better half will allow me near a computer at the time wink ). I'll be making use of the numerical modelling I've been working on and I'd like to see just how well it goes compared to the BoM models.

At this stage, I'll hazard a guess at a fairly warm start, maybe low-to-mid thirties with a strong nor'east sea breeze starting up around 11am EDT. Expect a front to pass southeast Australia maybe overnight on Boxing Day or sometime on Mon 27th. Can't tell at this stage just how strong that front may be though.

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#246264 - 21/12/2004 09:54 Re: Sydney Hobart race
thermalben Offline
Weather Freak

Registered: 17/04/2001
Posts: 769
Loc: Tweed Coast
This period is really shaping up to be quite dynamic. A decaying SWT looks like pasing through Melbourne on Xmas Day, but with little effect in the lower Tasman beside a small increase in groundswell from an earlier incarnation of the storm. However, there is strong agreement between EC and GFS for a significant cold outbreak across the region sometime during Mon 27th. Such a setup would deliver very strong and squally SSW winds to the Syd-Hob course, along with very large waves. I'll be watching this space closely over the next few days - at this stage, it appears that the timing couldn't be any worse (or better, depending on whether you're interested in good yacht racing - or severe marine weather that's likely to be well documented for a change wink

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#246265 - 21/12/2004 10:37 Re: Sydney Hobart race
barstardos Offline
Junior Member

Registered: 18/03/2004
Posts: 9
I was just looking at the models too and definitely looks like a major cold outbreak for the 27th with strong S-SE winds. Things could also get interesting for all the bushwalkers in Tasmania as potential low level snow and howling gales. I am also watching closely to see how much rain for western Tassie and if we will have the almost traditional flooding on the Franklin River for the Christmas-new year trips

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#246266 - 21/12/2004 16:59 Re: Sydney Hobart race
Milky06 Offline
Member

Registered: 11/08/2003
Posts: 863
Loc: Rockhampton, Qld - 23.2S 150.3...
This has come out of today WeatherZone Breaking Weather:

Flashback - Sydney to Hobart Yacht Race
Scott Rowe, Tue 16:36 EDT

The 1998 Sydney to Hobart yacht race was marred by a series of tragic events that lead to the death of 6 sailors attempting to complete the race. The primary cause of what unfolded 6 years ago was a small, deep low that quickly formed in the Tasman Sea during the early stages of the event. The low helped stir very rough seas and gale force winds which battered the yachts and caused many competitors to pull out.

Early indications from models for this year’s event show a similar setup. A low is predicted to form in roughly the same location and at the same time as six years ago, but it looks likely not to be as strong as in 1998. Models are disagreeing this far out on the position and intensity, however it will prove to be an event to watch as Boxing Day approaches.

Michael.

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#246267 - 21/12/2004 18:20 Re: Sydney Hobart race
teckert Offline
Weatherzone Moderator

Registered: 27/05/2001
Posts: 17706
Loc: NE suburbs, Adelaide, South Au...
Interesting to note that it has disapeared from Breaking Weather less than 2 hours after it was posted. Probably a good thing... not the greatest piece of writing IMO... frown

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#246268 - 22/12/2004 18:33 Re: Sydney Hobart race
Gulf Lines Offline
Banned member

Registered: 01/02/2001
Posts: 6369
I thought it was ok. I also liked the "ridiculous temps" as well (which was edited).

Seems that Scott might be a bit flamboyant for TWC. But I reckon he's great! Puts some life into the breaking weather stuff. laugh

Syd - Hobart - is not looking good for them. Time will be of the essence. I guess the sad thing is that the bigger yachts maybe back in port before the baddie arrives. The smaller guys may cop it tho! frown

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#246269 - 23/12/2004 09:22 Re: Sydney Hobart race
squared Offline
Junior Member

Registered: 16/12/2004
Posts: 3
Loc: Sydney
Thanks for all the replies.

Looks like the will be a considerable westerly componenent in the wind on the tassie coast for us at least until the night of the 28th
Does anyone think there will be any lee depression effect on the tassie coast? Would this bend the wind?
The EACC is better offshore but a little moderation of the wind/sea and perhaps a more favourable wind direction could make it worthwhile staying closer to Tasmania.

Any thoughts?

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#246270 - 23/12/2004 14:27 Re: Sydney Hobart race
inversion Offline
Weather Freak

Registered: 24/12/2003
Posts: 530
Loc: Melbourne
The models certainly seem to be agreeing on an active long wave trough (marked nicely on the 500hpa charts) resulting in a surge of cold air and a low pressure system forming between two slow-moving highs.

I think it's way too early to be able to accurately pinpoint the position, intensity and meso-scale effects of this low pressure system, but, going by the model agreement, we can probably fairly confidently expect strong to gale force winds at this stage (which are by no means abnormal for eastern Bass Strait)

However, mesoscale fluctuations can occur rapidly an unexpectedly in these sorts of systems, and so I will be keen to see what the meso-scale models do with the low, closer to the event

The lesson for this is indeed the 1998 event, where the broader-scale models didn't pick up the multiple meso scale low pressure centres which formed rapidly within the overall system and which strongly affected the wind intensity.

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#246271 - 23/12/2004 18:24 Re: Sydney Hobart race
Adiabatic Offline
Member

Registered: 01/09/2001
Posts: 14190
Loc: Knoxfield 96m: 120.2mm
Looking definantly like gales for this race, minimum 35-40 knot winds being an average and swells to about 5-6m. Some really rough conditions at this stage but it should be watched as invy said for changes to the meso-scale setup closer to the event, the chance that if the structure changes that winds will upgraded on the western side of this Tasman Low.

Karl smile

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#246272 - 24/12/2004 01:00 Re: Sydney Hobart race
majorowe Offline
Weather Freak

Registered: 27/01/2002
Posts: 242
Loc: SE France
I agree strongly with PaulM. I found the story informative and if it gets people interested in this sort of thing then that has to be a good thing. I am certainly going to watch what happens. Usually the leather and willow takes priority to the sea spray, but after reading about the 98 event and seeing the setup, I will pay more attention this year.

I would think 40C heat at 9:40am is ridiculous heat too.

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#246273 - 24/12/2004 20:04 Re: Sydney Hobart race
Craig Arthur Offline
Wind hazard researcher

Registered: 08/05/2001
Posts: 3549
Loc: 149.152009°E 35.187056°...
Certainly not looking as nasty as it was 24 hours ago. GFS has backed off considerably on the strength of winds along the TAS east coast on Monday night.

Currents
There's a strong southerly current flowing along the NSW coast - probably somewhere around 4 knots over the shelf off Jervis Bay - Batemans Bay - Narooma. Mainly due to a region of higher elevation centred 36S/152E. A small depression in sea level off Gabo Island means the current is almost reversed once you enter Bass Strait proper. However right in close to Gabo Is, there appears to be a narrow jet of southerly current - mainly between Merimbula and the NSW/VIC border. East of Flinders Island, the current swings back around to a southeasterly current. It's at this time hard to say what's going on close to the Tassie Coast with regard to the current.

Synoptic pattern
Sunday:
A weak high will bedeveloping over the NSW coast in the wake of the southerly change, and a trough will remain along the NSW ranges into northeastern VIC. The ridge will be very weak across VIC, with a deepening low pressure system centred southwest of TAS. This low will move rapidly east on Sunday afternoon, with the associated change lying through central Bass Strait (Melb-Devonport) by around 9Z-12Z. At this time, the ridge off the NSW coast will have strengthened slightly, increasing the pressure gradient between it and the trough over the western slopes. By 12Z the low should be south of TAS and deepening (central pressure ~995 hPa).
Monday:
LAPS is indicating the low won't intensify significantly as it passes south of TAS, but the high to the west will intensify to around 1028 hPa by 00Z Monday. The trough axis will be over the NSW south coast by this time, with a secondary weak trough lying over northeastern TAS. GFS on the other hand keeps the low significantly further south and faster-moving, although much deeper (~984 hPa).
Tuesday onwards:
The high pressure system should remain fairly slow moving in the Bight but will edge east, and the trough in the Tasman will deepen, so a persistence of the strong southwesterly flow can be expected. It should ease off slightly from the peak of the storm through Tuesday, as the high slowly edges east.

Winds
Sunday:
MLAPS has a light E/SE flow along most of the NSW coast on Sunday 00Z - around 15 kts (MLAPS is IMO notorious for under-predicting surface winds). Further south along the coast, with the developing ridge along the coast and the deepening inland trough, winds should trend around to the northeast in the afternoon, probably around the same speed. The synoptic set up doesn't look conducive to strong sea breezes, so it'll be mainly a gradient breeze and hence reasonably consistent offshore as well as in close. This also means the breeze should persist at a similar speed into the evening. Later in the evening I'd expect the winds to swing to the NW at around 10/15 kts, lighter and more variable inshore.
Monday:
As the main trough crosses VIC, NNW winds will slowly build through the early part of Monday monring probably up to 20/25 kts by dawn. LAPS shows the wind change reaching Gabo Is by 8am EDT (21Z Sun), similarly with GFS. It's difficult to say just how abrupt this change will be, but I'd err on the side of a gradual turning. The change will push up the coast in the following hours, and should be at Sydney by midday (01Z).
Both LAPS and GFS are indicating it could shift around to the SW immediately behind the change too, before veering to the WSW for a few hours and builds strength to 30/40 kts.
As the low slows down into later Mon, winds will back to the SW again and should continue to build slightly to a peak of 50 knots. GASP indicates a much more southerly scenario and potentially stronger winds, maybe mean winds up near 60 knots but this'll be into Tuesday morning.

As always, gusts are likely to be up to 50% more, so anything up to about 60 knots is probable on Mon afternoon and evening.

I tend to think that Monday will see the worst of the conditions, as the high will begin to dominate by Tuesday. I'm less a fan of GASP in general and prefer the GFS solution.

Seas/swell
Obviously, pretty big if it gets around to the south. With the current meandering around through Bass Strait and along the TAS coast, there's unlikely to be the steep waves develop that far south, so the bigger boats will fare better. Along the NSW coast though, there is a fair chance there will be some of those 'backless' waves due to the strength of the current. Sig wave heights are likely to be around 7 metres at the peak. Should be some huge surf along the NSW coast next week too. wink

I do think there'll be a significant lee trough off the TAS east coast if the low stays well south - that would lead to a more westerly flow across TAS and more likelihood of the lighter winds in close to the coast. If it's more the GASP/LAPS scenario with a dead southerly stream, then there's unlikely to be much protection along the east coast.

I'd be looking at getting as far south as possible before the initial change (obviously). That means getting offshore for the first few hours and out into the current. As the wind backs through to NW overnight Mon, track closer to the coast. I don't think it'll be too bad, as since the winds will be gradient as opposed to a sea breeze, they won't die out overnight. Only problem with that is it'll be a bit more flukey in close. I feel being in close early after the change will be better, as the seas will remain flatter but winds will be reasonably consistent across the track. Also, the core of the current is close to the coast near Gabo Is.

Crossing Bass Strait, there'll be no where to hide, because for a large part of the fleet, this is where they will encounter the strongest southerly winds. If the progs head for a more southerly stream on Mon/Tues, then heading towards the Flinders Group will probably be a slightly safer bet. If it's W/SW staying nearer the rhumb will be better to set you up for keeping off the TAS coast (avoiding the lee wave)a bit and in more consistent winds.

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#246274 - 24/12/2004 21:59 Re: Sydney Hobart race
bogong Offline
Weatherzone Addict

Registered: 05/10/2001
Posts: 1398
Loc: Canberra ACT (Higgins - NW Can...
Very interesting read Craig - will watch the models and developments with interest over the next 72 hours...

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#246275 - 25/12/2004 20:29 Re: Sydney Hobart race
thermalben Offline
Weather Freak

Registered: 17/04/2001
Posts: 769
Loc: Tweed Coast
Great write-up Craig - I'm most interested in the time frame between 12Z Mon and 00Z Tues, with the potential for an embedded secondary front within the SW'ly flow. As you mentioned, this is the period most likely to deliver the most damaging winds, and the smaller boats trailing at the back of the fleet are likely to be hit hardest, especially if the wind veers more southerly in direction. EC is suggesting another burst of squally S'ly winds for the race region later Wed too!

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#246276 - 25/12/2004 22:45 Re: Sydney Hobart race
squared Offline
Junior Member

Registered: 16/12/2004
Posts: 3
Loc: Sydney
Well I asked for gurus.
Thanks everybody, for the valuable information. Keep your eyes on Loki and see if we get it right.
Maybe I should have asked for a magician instead.... eek

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#246277 - 26/12/2004 09:39 Re: Sydney Hobart race
terrified Offline
Weatherzone Addict

Registered: 06/12/2001
Posts: 2131
Loc: Nowra nsw
Gday to All; :wave:

Firstly,hope you all had a nice christmas.. :wave:

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#246278 - 26/12/2004 18:11 Re: Sydney Hobart race
majorowe Offline
Weather Freak

Registered: 27/01/2002
Posts: 242
Loc: SE France
Fantastic write up Craig, well worth the read.

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#246279 - 26/12/2004 21:29 Re: Sydney Hobart race
Thunderstruck Offline
Lightning man

Registered: 10/05/2001
Posts: 15024
Loc: Seaford Meadows, SA
Skandia is a top yacht and I tip it to win again....pretty much best goin round atm with a top crew.

Skandia from Konica Minolta again, Nicorette not far behind them in 3rd.

For anyone interested there is a nice tracking site here of the positions of all the yachts.

http://rolexsydneyhobart.com/yacht_tracker.asp

TS cool

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#246280 - 28/12/2004 05:40 Re: Sydney Hobart race
terrified Offline
Weatherzone Addict

Registered: 06/12/2001
Posts: 2131
Loc: Nowra nsw
Morning to all;

The Super maxi "SKANDIA" was forced to retire from the race after damaging the keel. eek

Craig

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#246281 - 28/12/2004 09:24 Re: Sydney Hobart race
terrified Offline
Weatherzone Addict

Registered: 06/12/2001
Posts: 2131
Loc: Nowra nsw
Konica Minolta another casualty eek

Craig

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