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#1437472 - 16/10/2017 11:23 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: Mega]
Locke Offline
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Registered: 27/12/2007
Posts: 4361
Loc: Brisbane
Originally Posted By: Mega
GFS Extended has been predicting a fairly large WWB at the end of its run for a few days now. Let's hope it doesn't eventuate.


Just took a look at the most recent extended GFS run. In the shorter term the trades are pretty solid but turn to week westerlies for a few days at about 2 weeks out before the trades kick back in at the end of the run.
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This post and any other post by Locke is NOT an official forecast & should not be used as such. It's just my opinion & may or may not be backed by sound meteorological data. For official information, refer to Australian Bureau of Meteorology products.

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#1437481 - 16/10/2017 11:54 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
CoastalStorm22 Offline
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Registered: 10/07/2006
Posts: 2703
Loc: Lane Cove, Sydney, NSW
If the forecast MJO comes to fruition then I would not expect "weak" westerlies, Locke. It's a worry regardless given now quick it warmed after a simple easing of the trades recently.

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#1437484 - 16/10/2017 12:08 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
GringosRain Offline
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Registered: 19/06/2007
Posts: 1331
Loc: Quorrobolong NSW
what happens when those westerlies blow directly over where the coldest subsurface anomalies are? Can it drag them to the surface?

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#1437505 - 16/10/2017 14:12 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: GringosRain]
Mike Hauber Offline
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Registered: 13/07/2007
Posts: 2757
Loc: Buderim
Originally Posted By: GringosRain
what happens when those westerlies blow directly over where the coldest subsurface anomalies are? Can it drag them to the surface?


Short answer no.

First Coriolis force deflects the push at nearly 90 degrees, similar to how the push from high pressure towards low pressure results in winds nearly 90 degrees to the pressure gradient. This means that easterly winds to south of equator push water towards the south, and north of the equator push water towards the north. This creates a gap for cold water to come from beneath and results in a tongue of cool water along the equator.

With westerly anomalies the cooling effect of water from below is reduced or even blocked completely, and the sun warms up the water towards its more normal equatorial temperature of 30 degrees or so (water in the cool tongue can be as cool as 20 degrees in the far east). The cooling due to evaporation also reduces (except possibly in the case of extremely strong westerly wind bursts), and the currents bringing cooler water from the east weaken or reverse.

Strong westerly winds will be trying to push water from north and south towards the equator, and the cool subsurface water can be pushed deeper, where it is closer to the average temperature and so the subsurface cool pool can be weakened.

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#1437506 - 16/10/2017 14:23 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
ColdFront Offline
Meteorological Motor Mouth

Registered: 29/06/2008
Posts: 17918
Loc: Wide Bay..Near the beach
I wouldn't be getting too concerned about the effects of a forecast WWB any time soon. If it has an affect it will likely be very temporary.

Meanwhile cooling in the Southern Pacific has contiued the past 4 weeks and the cool anomalies have spread almost as far west as PNG. This bodes very well for the wet season in Nth Eastern Australia if it continues.

https://coralreefwatch.noaa.gov/satellit...fic_930x580.gif

30 day SOI now at +10.41 .
90 day SOI now at +7.47

Both well above BoM's LaNina threshold. Still a more than reasonable chance that they will call a La Nina very late, however BoM's rainfall forecast for the next 3 months does not support a response typical of La Nina. Though I tend to take them with a grain of salt that far out at this time of the year.

From BoM.

While unusual, it is not unheard of to see La Niña develop this late in the year. Of the late-developing La Niña events, their effect on summer rainfall has been mixed, with some leading to widespread above-average falls across eastern Australia, and others having minimal effect. The current 3-month rainfall outlook suggests only a 50% likelihood of wetter conditions in many parts of the country.
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#1437519 - 16/10/2017 16:14 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
CoastalStorm22 Offline
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Registered: 10/07/2006
Posts: 2703
Loc: Lane Cove, Sydney, NSW
On the other hand BOM also say this..

"Tropical Pacific Ocean temperatures may approach La Niña levels over the coming months. However, the corresponding warm sea surface temperatures that typically develop to the north and northwest of Australia during La Niña events are less likely to develop. This means that overall, effects upon Australia are likely to be reduced."

They are referring to late developing Nina's I believe.


Edited by CoastalStorm22 (16/10/2017 16:15)

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#1437527 - 16/10/2017 16:38 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7166
Loc: Adelaide Hills.
#1437353 - Yes smile ; I believe that is accurate.
Belinda Meneghini, Ian Simmonds and Ian N. Smith
[INTERNATIONAL JOURNAL OF CLIMATOLOGY Int. J. Climatol. 27: 109 – 121 (2007).]

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#1437554 - 16/10/2017 18:00 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: CoastalStorm22]
ColdFront Offline
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Registered: 29/06/2008
Posts: 17918
Loc: Wide Bay..Near the beach
Originally Posted By: CoastalStorm22


They are referring to late developing Nina's I believe.


Yes, and the rainfall in an "average" La Nina response is less likely in Western Qld and further west thereof as a result of the Indian Ocean. It could go either way in eastern Qld. Personally I feel it will be wet along the east coast if the current setup is maintained. The Indian Ocean is having little bearing on what is happening in Eastern Qld at the moment.
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#1437557 - 16/10/2017 18:24 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
CoastalStorm22 Offline
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Registered: 10/07/2006
Posts: 2703
Loc: Lane Cove, Sydney, NSW
Originally Posted By: ColdFront
Originally Posted By: CoastalStorm22


They are referring to late developing Nina's I believe.


Yes, and the rainfall in an "average" La Nina response is less likely in Western Qld and further west thereof as a result of the Indian Ocean. It could go either way in eastern Qld. Personally I feel it will be wet along the east coast if the current setup is maintained. The Indian Ocean is having little bearing on what is happening in Eastern Qld at the moment.


In your opinion how do you think it's looking for us poor parched southerners?

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#1437559 - 16/10/2017 18:37 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: CoastalStorm22]
ColdFront Offline
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Registered: 29/06/2008
Posts: 17918
Loc: Wide Bay..Near the beach
Originally Posted By: CoastalStorm22
Originally Posted By: ColdFront
Originally Posted By: CoastalStorm22


They are referring to late developing Nina's I believe.


Yes, and the rainfall in an "average" La Nina response is less likely in Western Qld and further west thereof as a result of the Indian Ocean. It could go either way in eastern Qld. Personally I feel it will be wet along the east coast if the current setup is maintained. The Indian Ocean is having little bearing on what is happening in Eastern Qld at the moment.


In your opinion how do you think it's looking for us poor parched southerners?


Averaged out your region doesn't enjoy the same benefit of Lanina nor the hindrance of El Nino that most of eastern Australia is affected by so it is difficult to know CS22.

See the map El Nino and La Nina
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#1437611 - 17/10/2017 02:45 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Bala26 Offline
Cloud Gazer

Registered: 23/09/2017
Posts: 2
What's the Latest MJO by BOM

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#1437617 - 17/10/2017 07:16 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Locke Offline
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Registered: 27/12/2007
Posts: 4361
Loc: Brisbane
Most of the latest model runs seem to have it weakening as it enters phase 6.

Latest extended GFS shows weakening of the trades as the MJO passes through but no WWB that I can see. Some strong trades prior to this.
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This post and any other post by Locke is NOT an official forecast & should not be used as such. It's just my opinion & may or may not be backed by sound meteorological data. For official information, refer to Australian Bureau of Meteorology products.

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#1437618 - 17/10/2017 07:19 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
mammatus meestrus Offline
Cloud Gazer

Registered: 20/11/2008
Posts: 40
Loc: lennox head
If it looks like a duck and quacks like a duck it's close enough to a duck for me.

Global SST anoms, current deep easterly moisture infeed.
Feels like a full blown monsoonal pattern typical of a Nina year here right now.

And it's only October.

Any reversal is going to have a helluva time reversing this pattern.

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#1437621 - 17/10/2017 07:49 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: mammatus meestrus]
Kino Offline
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Registered: 10/08/2017
Posts: 1269
Loc: Wollongong, NSW, Aus
Originally Posted By: mammatus meestrus
If it looks like a duck and quacks like a duck it's close enough to a duck for me.

Global SST anoms, current deep easterly moisture infeed.
Feels like a full blown monsoonal pattern typical of a Nina year here right now.

And it's only October.

Any reversal is going to have a helluva time reversing this pattern.


Exactly - deep feed moist easterlies very symptomatic of La Niña type setup. As well, Western USA classic La Niña conditions. Hope it continues and pushes into central & coastal NSW where it’s dry dry dry frown

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#1437637 - 17/10/2017 09:16 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Mike Hauber Offline
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Registered: 13/07/2007
Posts: 2757
Loc: Buderim
Rapid cooling in the east again, and nino 3.4 is down to -0.38, which is 0.04 cooler than the previous lowest 5 weeks ago. Nino 3 has dropped to -0.39 which is 0.52 warmer than the previous coolest of three weeks ago. Overall the equatorial pacific is about the same temperature it was 4 weeks ago.

Nino 4 is still just barely positive at 0.04, so still no significant cooling far enough west to shift tropical convection west from its normal position and so sustain a La Nina atmospheric feedback. (Cool anomalies are in this region, but are not substantial enough to ofset the warm anomalies near the equator within the nino 4 measurement region) This is also the region that will influence the MJO as it enters the western Pacific.

MJO forecasts for the western Pacific for EC and CFS range from slight weakening to quite strong. Some others such as BOM are going for minimal MJO in west Pacific.

GFS forecasts westerly winds to appear as early as day 5 now. The westerlies back off but then reintensify and at day 13 they aren't strong, but quite extensive with westerlies reaching the dateline, which outside of the 97/98 event is rather uncommon.
EC Supports GFS to day 10 with just barely westerlies on day 5, and again on day 10. Warming does not require actual westerly winds, and even a reduction of trade winds to below average can be enough for warming, so just barely westerly is significant.

Finally CFS continues to forecast a very strong westerly wind burst throughout the Pacific in around 2 weeks time.

The last strong westerly wind forecast I commented on was not nearly as strong as forecast. I don't think it had the same level of model agreement, and did not have MJO support. It was still enough to almost totally wipe out the cool tongue within the space of about two weeks.

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#1437645 - 17/10/2017 09:57 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Locke Offline
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Registered: 27/12/2007
Posts: 4361
Loc: Brisbane
It didn't "almost totally wipe out the cool tongue". In fact it had minimal overall impact across a small portion of the overall area.

_________________________
This post and any other post by Locke is NOT an official forecast & should not be used as such. It's just my opinion & may or may not be backed by sound meteorological data. For official information, refer to Australian Bureau of Meteorology products.

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#1437648 - 17/10/2017 10:05 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: Mike Hauber]
Kino Offline
Weatherzone Addict

Registered: 10/08/2017
Posts: 1269
Loc: Wollongong, NSW, Aus
Originally Posted By: Mike Hauber
The last strong westerly wind forecast I commented on was not nearly as strong as forecast. I don't think it had the same level of model agreement, and did not have MJO support. It was still enough to almost totally wipe out the cool tongue within the space of about two weeks.


If this is "totally wiped out" then huh?

The issue I have is that the Nino areas are based on what, one or 2 buoys in the area? But as can be seen below, they may be in an eddy of warmer water while clearly the "zone" is colder?



Edited by Kino (17/10/2017 10:06)

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#1437649 - 17/10/2017 10:07 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Kino Offline
Weatherzone Addict

Registered: 10/08/2017
Posts: 1269
Loc: Wollongong, NSW, Aus
Interesting variance between NCEP and NOAA too in the SST's anomalies.

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#1437650 - 17/10/2017 10:07 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
ColdFront Offline
Meteorological Motor Mouth

Registered: 29/06/2008
Posts: 17918
Loc: Wide Bay..Near the beach
I bit my tongue.
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#1437652 - 17/10/2017 10:15 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Kino Offline
Weatherzone Addict

Registered: 10/08/2017
Posts: 1269
Loc: Wollongong, NSW, Aus
Hmmmmm NCEP has Coral Sea significantly warming whereas NOAA has it cooling in some areas.

And I would think the BoM's call for an average TC season is a significant over-reach IF the Eastern Indian continues the way it is. I'd say a another below-average season ahead unless there's a massive turnaround in a short time (the Leeuwin current / Indonesian flow-through appears to be having little influence as yet).

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