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Old 28-07-2018, 08:02   #1
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Weather across the Great Australian Bight,

These are a few piccys of the wave heights and winds forecasts for the next week,
Across The Great Australian Bight,

Its the ocean underneath the Southern Coast of Australia,
Its apparently an unnamed Ocean as Its not the Southern Ocean as I thought it was,
Only ocean in the world with no name, hahahahaha

Taken at 1600 each day, The wave heights are in metres,
Roughly, Multiply by 3 to get approx feet,
Its a prediction put out by the Burue of Meteriology, Australia, Its their Maps,
Its a govt Department,

They are not in order, But you can see by the dates on them which ones are which,
This is one ocean that I am very wary of, And picking good weather windows to cross it is a must,
It does get some very big waves across there,

The south east coast of Australia has 1 metre waves for the next week,

Its just a point of interest,

Cheers, Brian,
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Old 28-07-2018, 08:46   #2
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Re: Weather across the Great Australian Bight,

See International Hydrographic Organisation S-23 Limits of Oceans and Seas.


It's a sub-division of the Indian Ocean - specifically, 5.17 The Great Australian Bight.
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Old 28-07-2018, 09:43   #3
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Re: Weather across the Great Australian Bight,

It gets a bit conflicting,
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Old 28-07-2018, 15:51   #4
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Re: Weather across the Great Australian Bight,

Quote:
Originally Posted by Mr B View Post
It gets a bit conflicting,

Yep, it depends on who you ask. The International Hydrographic Organisation (IHO) Limits of Oceans and Seas is generally recognised as an authoritative source, but it's not definitive.

According to the IHO 1928 delineation, it was part of the Southern Ocean.
According to the 1937 delineation, it was a separate entity, the Great Australian Bight.
According to the 1953 delineation, it is still the Great Australian Bight but also became past of the Indian Ocean. (And there is no such thing as the Southern Ocean)
According to the draft 2002 delineation, it is still the GAB, but sailing south, you go from the GAB to the Indian Ocean then the Southern Ocean as you head towards Antarctica.

But not everyone works according to the IHO delineations. The Australian Government and hence the Australian Hydrographic Service (part of the Navy) being dissenters



To them, it's still part of the Southern Ocean in accordance with old Australian legislation. To quote the official Australian Government, Geoscience Australia website:


Australian Ocean Governance and Relevant Legislation - Geoscience Australia


"The extent of Oceans and Seas are described in the International Hydrographic Organisation publication 'limits of the Oceans and Seas 1953'(S23). Australia disagrees with limits of the Southern Ocean as defined in this publication."
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Old 28-07-2018, 16:04   #5
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Re: Weather across the Great Australian Bight,

Quote:
Originally Posted by StuM View Post
To them, it's still part of the Southern Ocean in accordance with old Australian legislation.
Yes, that's it ... the Aussie adherence to the philosophy of empty nominalism, the idea that if the Aussie parliament passes a law (about an ocean, citizenship, etc) then it must be true.

See: Can I refer to my catamaran as a ship?
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Old 28-07-2018, 16:24   #6
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Re: Weather across the Great Australian Bight,

You are right Mr B, there are some big waves out there!
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Old 28-07-2018, 16:43   #7
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Re: Weather across the Great Australian Bight,

Quote:

To them, it's still part of the Southern Ocean in accordance with old Australian legislation. To quote the official Australian Government, Geoscience Australia website:


Australian Ocean Governance and Relevant Legislation - Geoscience Australia


"The extent of Oceans and Seas are described in the International Hydrographic Organisation publication 'limits of the Oceans and Seas 1953'(S23). Australia disagrees with limits of the Southern Ocean as defined in this publication."
Yet the Australian Antarctic Division ( folks who actually know something about the subject!) says that the SO's northern limit is at 40 deg S. in most areas. Don't these guys talk to each other?

Actually, I can understand not wanting to talk to Parliamentarians! As a retired boffin, I remember disliking such conversations!

Jim
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Old 28-07-2018, 17:08   #8
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Re: Weather across the Great Australian Bight,

Quote:
Originally Posted by Jim Cate View Post
Yet the Australian Antarctic Division ( folks who actually know something about the subject!) says that the SO's northern limit is at 40 deg S. in most areas. Don't these guys talk to each other?

They actually talk about the Southern Sub Tropical Front as the northern boundary. According to the American Meteorological Society:


In the Southern Hemisphere, the subtropical front can be traced from 40°S at the east coast of South America across the Atlantic into the Indian Ocean and across the Great Australian Bight, where it shifts to 45°S to pass south of Tasmania and reach the southern tip of New Zealand's South Island. It continues in the Pacific Ocean from the Chatham Rise east of New Zealand near 40°S and reaches the west coast of South America near 30°S.

Had me worried there for a while. that 40° put Tassie and the South Island of NZ squarely in the Southern Ocean
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Old 28-07-2018, 17:20   #9
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Re: Weather across the Great Australian Bight,

I guess we've hijacked Mr B's thread enough now.

Back to the waves....

That forecast didn't seem too bad to me until I realised that the BOM uses different scales in different places. That yellow 5-6 metres would only be 2-3 metres on the forecasts I generally look at:
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Old 28-07-2018, 17:43   #10
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Re: Weather across the Great Australian Bight,

Quote:
Originally Posted by StuM View Post
I guess we've hijacked Mr B's thread enough now.

Back to the waves....

That forecast didn't seem to bad to me until i realised that the BOM use different scales in different places. That yellow 5-6 metres would only be 2-3 metres on the forecasts I generally look at:
Yep, that has caught me too (but in reverse)!
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Old 28-07-2018, 17:53   #11
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Re: Weather across the Great Australian Bight,

Quote:
Originally Posted by StuM View Post
I guess we've hijacked Mr B's thread enough now.

Back to the waves....

That forecast didn't seem to bad to me until i realised that the BOM use different scales in different places. That yellow 5-6 metres would only be 2-3 metres on the forecasts I generally look at:
Bom use the same scales all around OZ, But the East coast of OZ, usually a really big wave is around 4 metres,
6 metres in a cyclone,
Normally the east coast of oz is around a metre or two, Pleasant sailing in most weathers,

GAB, is an ocean on its own, Forty foot and above waves are common down them,
It can also be a millpond, With no wind to sail in,

Watch a few youtube video's, Crossing the Bight in bad weather on a cat or a Yacht,

The Princess of Tasmania coming thru the Rip in Bad weather is a good one,
The video was taken from the cliffs at Portsea,
I bet every one on board was chucking their guts on that trip, Hahahaha
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Old 28-07-2018, 18:05   #12
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Re: Weather across the Great Australian Bight,

Wave heights at the eastern limits of the Indian Ocean......
BoM - Cape Sorell Waverider Buoy Observations
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Old 28-07-2018, 19:34   #13
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Re: Weather across the Great Australian Bight,

Port Philip Heads, The regulars, Is a very good video on Youtube,
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Old 28-07-2018, 20:27   #14
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Re: Weather across the Great Australian Bight,

Quote:
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Bom use the same scales all around OZ, But the East coast of OZ, usually a really big wave is around 4 metres,
6 metres in a cyclone,
Sorry, I didn't mean different places around Oz, I meant different places on their website. i.e. AUSWAVE v MetEye charts. Both are waveheight charts around Oz, but the colour scales are very different.
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Old 29-07-2018, 03:03   #15
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Re: Weather across the Great Australian Bight,

I departed Fremantle going north to passage across the top back to Queensland during July last year and during the good weather windows I was using to get north the weather forecast from BOM was predicting 5.5m - 6.5m with their usual warning that wave heights could be up to 40% higher than the averages given.

Once I got into deep water they were not too scary however from Fremantle to Geraldton there is a coastal shelf and when the damned things hit the shelf they get slowed down and steepen and the height increases.

I came out of Jurian Bay after a four day SW blow and I'll swear the damned things were 10m high where passing onto the 12m-15m water depth of the shelf. However, since the tops were not in any way starting to curl over I decided that I'd have a go and see if the boat would actually climb over them. The interesting thing is that the boat did not appear to slow down at all. The scariest part was when I was on the top of the wave and looked down the back side and saw the next one coming.

I am not going back to that place ever again during the winter months.
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