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#493785 - 09/07/2006 00:25 I am backing another weak La nina
*Runoff* Offline
Member

Registered: 24/01/2005
Posts: 2209
Loc: Whitsundays
After seeing a warming across most of the equatorial pacific over the last few months the trend seems to be reversing. Stormsurf's comparisons to this time last year show some strong similarities albeit slightly warmer. If these large high pressure systems keep going through until spring , my guess is we will have another reasonably wet summer.

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#493786 - 14/07/2006 21:24 Re: I am backing another weak La nina
Inclement Weather Offline
Meteorological Motor Mouth

Registered: 07/03/2006
Posts: 5373
Loc: Diamond Valley
I hope you're right runoff . . .
_________________________
The original donut hole

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#493787 - 14/07/2006 21:55 Re: I am backing another weak La nina
Peng Offline
Member

Registered: 13/01/2006
Posts: 2122
Loc: Monash Uni Clayton/Sale, Victo...
Maybe we could base a decision on the outcome of this current rain event in Eastern Australia... wink

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#493788 - 17/07/2006 07:54 Re: I am backing another weak La nina
*Runoff* Offline
Member

Registered: 24/01/2005
Posts: 2209
Loc: Whitsundays
A BoM employee made the comment this week that it is most unusual to see high pressure systems centred so far south at this time of year. The current high is forecast to peak at 1037hpa in the Tasman sea and direct further showers on to the east coast. He also said that although the remaining winter rainfall outlook is below average , the chances of showers continuing along the tropical east coast are above average. Over the past fortnight these SE trade winds have further reduced the warming trend in the equatorial pacific.

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#493789 - 17/07/2006 09:28 Re: I am backing another weak La nina
Rainy Night Offline
Weatherzone Addict

Registered: 01/02/2004
Posts: 4267
Loc: Jindalee, Brisbane
It would also be helpful if the SOI were to return to positive values - however it is quite commonly negative at this time of year. The key time for a rise in the SOI is between usually between August and November to be helpful towards a La Nina situation and enchancement of summer/tropical wet season rainfall. As you mention, the current situation is encouraging - also perhaps a La Nina is overdue, since there have been mostly either neutral or El Nino conditions in the last decade or so - so you may well be right there - let's hope so! smile

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#493790 - 17/07/2006 22:50 Re: I am backing another weak La nina
adon Offline
Meteorological Motor Mouth

Registered: 19/08/2004
Posts: 5339
Loc: Not tellin!
Hopefully the next La Nina is a strong one. Maybe that will break this pattern of late breaks and drier springs. I remember a climate discussion a while ago that said that neutral conditions could be no better than El Nino for some parts of the country. Reckon this area must be one of the parts! La Nina has to be overdue. We have not seen the creeks in the Mallee run since I finished school (10 years ago). The current phase we are in has to change soon surely.

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#493791 - 18/07/2006 15:50 Re: I am backing another weak La nina
eternal rain Offline
Member

Registered: 10/07/2004
Posts: 5685
Loc: the great sydney desert
Yeah runoff, your forecast and guesses seem about right to me. I ran some AVN plots last night for the broad central pacific area and what it seems to be saying is that this strong high is one of many which will dominate the south pacific starting from next week. should this happen we will see rapid strengthening of the trade winds from east to west. In the northern hemisphere the north pacific is also under the influence of a strong high which is helping with the trade winds. Another thing of interest is the strength of the jet stream over central australia atm, brisbane sounding registered 150 knots at 300hpa, very strong and unusual. These jets will help pull the easterly winds further and help warm our oceans too. In the last 3-5 days, SSTs around the country have started to warm up considerably which may be the sign of things to come. We made similar forecasts last year and the wet season didnt deliver much, lets hope this one does.

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#493792 - 18/07/2006 16:24 Re: I am backing another weak La nina
Keith Offline
Meteorological Motor Mouth

Registered: 16/12/2001
Posts: 6453
Loc: Kings Langley, NSW
As much as I hate to be a wet blanket, the latest tropical climate update here says that we are showing signs of a weak El Nino, just as it was showing a weak La Nina some time back. The outlook is for essentially neutral conditions, although there's a sign that the warming in the eastern Pacific has peaked. So Boris I hope you are right!
:cheers:

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#493793 - 18/07/2006 16:37 Re: I am backing another weak La nina
*Runoff* Offline
Member

Registered: 24/01/2005
Posts: 2209
Loc: Whitsundays
I am basing my belief on the warming having peaked. I hope it has. Still early days yet but these large highs might just help shove things back the other way. Also the cooling on the east pacific thermocline appears to have intensified over the past fortnight. As you mentioned Keith there is a weak warm pool off Sth America , however there was last year also. Though it wasn't as strong.

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#493794 - 18/07/2006 17:57 Re: I am backing another weak La nina
sugar mill tour guide Offline
Member

Registered: 09/07/2004
Posts: 1817
Loc: Proserpine North qld
okay well cainfarmers here r sniffing a early wetseason. I reckon the same thing as the water temp off our coast in majorily warmer than usal. Im fellin rather worried cause that means my job on the line

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#493795 - 23/07/2006 11:20 Re: I am backing another weak La nina
eternal rain Offline
Member

Registered: 10/07/2004
Posts: 5685
Loc: the great sydney desert
Well as i said in my post a few days ago about the strong highs which will establish themselves over the south pacific to help get the trade winds going. The predicted strong high has emerged and is sitting over that exact forecasted spot as 1041hpa. It has weakened to 1040hpa this morning but still remains a strong system.

Just to give u an idea of what im talking about, heres the plot i ran:

http://nomad3.ncep.noaa.gov/tmp/ATEST23377.png

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#493796 - 23/07/2006 11:33 Re: I am backing another weak La nina
adon Offline
Meteorological Motor Mouth

Registered: 19/08/2004
Posts: 5339
Loc: Not tellin!
How long is that forecasted to be there Bokkey? Certainly is a big bugger!

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#493797 - 23/07/2006 12:07 Re: I am backing another weak La nina
eternal rain Offline
Member

Registered: 10/07/2004
Posts: 5685
Loc: the great sydney desert
Well that set up remains unchanged in the forseeable future, the big high in the northern hemisphere and a few coupled in the southern hemisphere, so hopefully it stays that way for a longer time smile

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#493798 - 25/07/2006 23:57 Re: I am backing another weak La nina
adon Offline
Meteorological Motor Mouth

Registered: 19/08/2004
Posts: 5339
Loc: Not tellin!
That high in the Pacific doesn't seem to be making a huge diff to the SOI. Looks like it is still going in the same pattern it has for ages now.

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#493799 - 26/07/2006 08:35 Re: I am backing another weak La nina
Tempest Offline
Weatherzone Addict

Registered: 17/11/2001
Posts: 3633
It seems as though a weak el-nino is building rather than la nina.

SST\'s

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#493800 - 26/07/2006 12:28 Re: I am backing another weak La nina
eternal rain Offline
Member

Registered: 10/07/2004
Posts: 5685
Loc: the great sydney desert
The east pacific has warmed recently to weak el nino status, but the sub-surface temp anomaly maps indicate a cooling in that sector of the ocean atm and also indicate a cooler upwelling starting to occur from a mass 50-150metres below this. Charts still forecast highs to linger across south pacific and a strong high in the north. hopefully they are strong enough to force these winds westward which should already be flowing that way.

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#493801 - 26/07/2006 16:23 Re: I am backing another weak La nina
*Runoff* Offline
Member

Registered: 24/01/2005
Posts: 2209
Loc: Whitsundays
Yeah I saw that too Bokkey. The footprint for a La nina is looking less convincing though. Although the trop note did mention that they felt the warming had peaked in June. Fingers crossed.

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#493802 - 26/07/2006 22:34 Re: I am backing another weak La nina
adon Offline
Meteorological Motor Mouth

Registered: 19/08/2004
Posts: 5339
Loc: Not tellin!
Prolly not the right place to ask this but how does the Pacific cool at depth? Is it Because of upwelling due to warmer water being moved by wind or is it just pooling under warmer water with a cold current?

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#493803 - 27/07/2006 14:29 Re: I am backing another weak La nina
*Runoff* Offline
Member

Registered: 24/01/2005
Posts: 2209
Loc: Whitsundays
You are in the right place Adon. It is a combination of a number of things including all that you mentioned above. The water movement on the thermocline at around 150 mtrs deep plays the biggest role. However strong surface winds are a significant factor also. For us to have a real chance at a decent wet we need to see the surface winds of Sth America start blowing back towards Australia. This will push the warm surface water back towards us and enable the cold water (currently suppressed beneath the warm pool) to surface. Strong westerly wind burst up around the solomons have an opposite effect. They drive warm water down to the thermocline which then moves east and surfaces on the equator off the coast of sth America .As this warm pool spreads back toward the centre of the pacific it increase our chances of an El Nino forming. It is actually the strength of the event that determines how much rain we will get or miss out on . A weak el nino has little bearing on Australia's rainfall. The warm water needs to spread back to near the dateline for there to be a major effect on our weather. There are many more factors that affect it , but anyway I hope this sheds some light.

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#493804 - 27/07/2006 16:11 Re: I am backing another weak La nina
Proteus Offline
Member

Registered: 08/08/2005
Posts: 702
Loc: Paynesville on the Gippsland L...
Necrotising arachnidism usually associated with an over active Cheliceraeis is one of the best indicators of SST anomilies I've seen. However if the Epigynum twitches periodically except when
an Epigastric furrow is evident then your really back to square one.

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