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#1447940 - 08/01/2018 09:06 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
ozone doug Offline
Weatherzone Addict

Registered: 06/11/2006
Posts: 1808
Loc: Roma SW QLD Eye to the West...
Nice links guys ,Some good discussion going on here.
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#1447949 - 08/01/2018 11:10 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Mike Hauber Offline
Weatherzone Addict

Registered: 13/07/2007
Posts: 3123
Loc: Buderim
Tropical convection looks to be going very strong in the Indian Ocean (chart)

Solid high pressure in Pacific pushing trades all the way through the far north Australian region, suppressing the monsoon and feeding into the activity in Indian Ocean. Little change in the forecast period. Some spill of tropical activity into west Australia, eg the charts Mega posted where the Indian Ocean activity has weakened a bit, before it surges again later in the forecast (at 10 days questionable reliability).

More La Nina like would be to have the low pressure region over Australia and not over the Indian Ocean. SOI has dropped like a stone with 30 day now at 0.6, and judging by forecasts might go -ve in the next few days as this pattern continues in at least the short term. MJO forecast to move steadily towards Australia in EC which should shift the pattern, but GFS has it stalling in Indian.

Curiously with strong activity in the Indian, SSTs are on the cool side IMO. A balance between warm and cool, hard to tell which is dominant, but most of the time recently Indian has been a lot warmer. As well as the frequently discussed IOD aspect, I've seen research suggesting warm Indian ocean overall makes Australian drought more likely and cool is favourable for rain. Maybe its a case of enhanced Indian Ocean activity causing the SSTs to cool. But then what causes the enhanced Indian Ocean activity if not warm SSTs?

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#1448023 - 08/01/2018 21:37 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: snowbooby]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7468
Loc: Central Adelaide Hills
Originally Posted By: snowbooby
Also changes in phase of AMO->intensification of Pacific ST High->stronger than average background Trades->strengthening ST Pacific coupling(wind-evaporation-sst feedback)->ST Pacific Precursors more capable of penetrating into deep tropics

Bold - Yes smile , may also be known as the WES Feedback, probably related to the seasonal migration of the ITCZ (from what I've read). May bring the Bjerknes Feedback into the picture more.


Edited by Seira (08/01/2018 21:46)
Edit Reason: Name Correction
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#1448026 - 08/01/2018 22:21 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: Seira]
snowbooby Offline
Weather Freak

Registered: 11/05/2016
Posts: 170
Originally Posted By: Seira
Originally Posted By: snowbooby
Also changes in phase of AMO->intensification of Pacific ST High->stronger than average background Trades->strengthening ST Pacific coupling(wind-evaporation-sst feedback)->ST Pacific Precursors more capable of penetrating into deep tropics

Bold - Yes smile , may also be known as the WES Feedback, probably related to the seasonal migration of the ITCZ (from what I've read). May bring the Bjerknes Feedback into the picture more.

That work I was attempting to summarise - unfortunately the links I've since found no longer allow successful download - it was a journal publication and I wonder it may be restricted or subscription access now.

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#1448037 - 09/01/2018 00:21 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: snowbooby]
marakai Offline
Weatherzone Addict

Registered: 05/01/2006
Posts: 1841
Loc: Maryfarms NQ
Quote:
OK. I'll see if I can sort that out - I downloaded it myself but it was some months ago

Alternately "Precursors of Enso beyond the tropical Pacific"
Jin-Yi Yu and Houk Paek may find it if you wish to try different link


https://www.ess.uci.edu/~yu/PDF/Yu.US%20CLIVAR%20Variations.2015%20winter.pdf


Edited by marakai (09/01/2018 00:22)

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#1448058 - 09/01/2018 08:26 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
CoastalStorm22 Offline
Weatherzone Addict

Registered: 10/07/2006
Posts: 2806
Loc: Lane Cove, Sydney, NSW
Whether it holds or not the reversal of the SOI in the last 30 days has been rather dramatic.
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#1448230 - 10/01/2018 03:14 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Dusty Rusty Offline
Cloud Gazer

Registered: 30/01/2017
Posts: 13
Loc: Capricorn Region
All indications suggest that the wet season is over, it was weak & short lived.
Time to get back to business now the wet season is over. Time to plough the bottom paddock. BOM has no idea what they are doing, forecasting La Niņa during one of the dryest Januarys on record.

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#1448232 - 10/01/2018 06:28 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Chris Stumer Offline
Weatherzone Addict

Registered: 28/01/2010
Posts: 1790
Loc: Kingaroy
We still have February, March and April, there is still time. GFS still has that trade burst going on so La Nina could start to strengthen hopefully.

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#1448243 - 10/01/2018 09:02 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Petros Offline
Meteorological Motor Mouth

Registered: 30/12/2002
Posts: 7058
Loc: Maffra, Central Gippsland, Vi...
It seems that the warm water/persistent troughing around NZ encourages that coastal ridge along Qld coast. Seems that the ridge will return again for a period later this week into early next week before weakening allowing a wetter period from mid next week to set in over larger areas of Qld.

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#1448264 - 10/01/2018 11:42 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
ashestoashes Offline
Weather Freak

Registered: 22/10/2017
Posts: 365
Loc: Voyager Point (South West Sydn...
Apparently the monsoon trough is supposed to lengthen to bring rainfall fingers crossed for you Far North Queenslanders this eventuates.
Weekly Tropical Note BOM

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#1448266 - 10/01/2018 11:56 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Mike Hauber Offline
Weatherzone Addict

Registered: 13/07/2007
Posts: 3123
Loc: Buderim
30 day SOI down to -4.5. Monthly SOI for December was -1.4. SOI is by far the best indicator of ENSO influence on Australian rainfall, and the December SOI suggests a weak dry influence.
The problem with SOI is that it can turn on a dime and is much harder to predict than nino 3.4 etc, which is why all the discussion and modelling is usually on the SSTs.

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#1448268 - 10/01/2018 11:59 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Kino Offline
Weatherzone Addict

Registered: 10/08/2017
Posts: 2267
Loc: Wollongong, NSW, Aus
SOI will change markedly by next week - monsoon trough here and going to deepen; MJO pushing here and persistent low pressure near Darwin. Watch it bounce back dramatically.

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#1448269 - 10/01/2018 12:03 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: Petros]
Mega Offline
Meteorological Motor Mouth

Registered: 03/02/2003
Posts: 7018
Loc: Maryborough, Wide Bay, QLD
Originally Posted By: Petros
It seems that the warm water/persistent troughing around NZ encourages that coastal ridge along Qld coast. Seems that the ridge will return again for a period later this week into early next week before weakening allowing a wetter period from mid next week to set in over larger areas of Qld.


Honestly that troughing seems to be there whether the waters in that area are warm or not. Not sure why. Next big shortwave conveniently stays south as it's passing across southern Australia but then magically amplifies once it's hit the Tasman Sea on the weekend. As a result we're left with more drier SSE'lies pushing up from Antarctica behind the stupid low followed by more weak high pressure cells in the northern Tasman (when they should be further south). I was under the impression that La-Nina was supposed to encourage ridging through the southern Tasman Sea which then feeds into troughing over Australia...which mostly isn't happening (the coast is doing better under thunderstorms from W > E shortwave troughs) but the long onshore flows which lead to big rain events seem to be missing at the moment.

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#1448270 - 10/01/2018 12:16 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: Mega]
Kino Offline
Weatherzone Addict

Registered: 10/08/2017
Posts: 2267
Loc: Wollongong, NSW, Aus
Originally Posted By: Mega
Originally Posted By: Petros
It seems that the warm water/persistent troughing around NZ encourages that coastal ridge along Qld coast. Seems that the ridge will return again for a period later this week into early next week before weakening allowing a wetter period from mid next week to set in over larger areas of Qld.


Honestly that troughing seems to be there whether the waters in that area are warm or not. Not sure why. Next big shortwave conveniently stays south as it's passing across southern Australia but then magically amplifies once it's hit the Tasman Sea on the weekend. As a result we're left with more drier SSE'lies pushing up from Antarctica behind the stupid low followed by more weak high pressure cells in the northern Tasman (when they should be further south). I was under the impression that La-Nina was supposed to encourage ridging through the southern Tasman Sea which then feeds into troughing over Australia...which mostly isn't happening (the coast is doing better under thunderstorms from W > E shortwave troughs) but the long onshore flows which lead to big rain events seem to be missing at the moment.


Models are going to dynamically change IMO as there's a huge surge of cold ne'er's heading our way from the South China sea, significantly amplifying the monsoon trough. Expect Hadley Cell (read STR as well) to then push further south.

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#1448278 - 10/01/2018 12:46 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
NotsohopefulPete Offline
Weatherzone Addict

Registered: 24/12/2008
Posts: 1194
Loc: Toowoomba
Well Mega, when I saw the latest EC upper pattern and even with my limited ability to read them and the huge upper trough/low that surges out into the Tasman and stays forever I thought of you. You seem to understand the devastating effects it has on rain over SE QLD and NE NSW. You can get 20 cyclones over the Gulf that will move west and hit WA and 20 over the Coral sea and they will all roar off to the SE, then New Zealand. Of course, I am hoping like crazy, that the others like Kino are right and this pattern ends soon.
Cheers


Edited by NotsohopefulPete (10/01/2018 12:48)

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#1448285 - 10/01/2018 13:49 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Mike Hauber Offline
Weatherzone Addict

Registered: 13/07/2007
Posts: 3123
Loc: Buderim
According to the models the surge of NEs won't do anything noticeable to push the Hadley Cell further south, and at the end of the run the Ridge stays firm which holds the westerlies near the equator as they start to enter the West Pacific for possibly the next WWB.

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#1448286 - 10/01/2018 14:02 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Kino Offline
Weatherzone Addict

Registered: 10/08/2017
Posts: 2267
Loc: Wollongong, NSW, Aus
BoM disagrees:

Originally Posted By: BoM
The focus of tropical rainfall during much of the coming week will be in the region affected by the developing tropical low over Western Australia. Model guidance generally indicates that a weak monsoon trough will persist over northern Australia during this period. There are also indications that a surge of wind through the South China Sea (not observed in recent days) may develop and cross the equator and feed into the pre-existing monsoon trough in the Australian region. Depending on the status and location of the potential tropical cyclone over Western Australia, this wind surge could potentially invigorate the monsoon trough and lead to some widespread rainfall across northern Australia later in the week.

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#1448290 - 10/01/2018 15:06 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Mike Hauber Offline
Weatherzone Addict

Registered: 13/07/2007
Posts: 3123
Loc: Buderim
Widespread rainfall across northern Australia or invigoration of the trough does not mean the Hadley Cell will push south or that the ridge will weaken, or that westerlies can't enter the western Pacific.

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#1448291 - 10/01/2018 15:11 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: Mike Hauber]
Kino Offline
Weatherzone Addict

Registered: 10/08/2017
Posts: 2267
Loc: Wollongong, NSW, Aus
Originally Posted By: Mike Hauber
Widespread rainfall across northern Australia or invigoration of the trough does not mean the Hadley Cell will push south or that the ridge will weaken, or that westerlies can't enter the western Pacific.



The dynamics of the Hadley Cell and it's relationship with the monsoon trough absolutely mean the Hadley Cell will dip south - the 2 are inextricably linked.



Edited by Kino (10/01/2018 15:13)

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#1448294 - 10/01/2018 15:48 Re: Climate Driver Discussion 2018 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Mike Hauber Offline
Weatherzone Addict

Registered: 13/07/2007
Posts: 3123
Loc: Buderim
Models show no general southward movement of the monsoon trough, so no pressure on the Hadley Cell to move south. Invigoration of the trough does not mean it has to move south.

In many cases when the Monsoon trough moves south it does so locally and the High pressure belt responds by thinning to the south, and thickening further east and west without necessarily moving further south. Some of the N-S circulation gets transferred to E-W circulations.

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