Current & Forecast Climate Drivers

Mega

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It’s incredible watching the forecast models chop and change each month. I feel like the whole atmosphere is hanging by a thread and it will only take another big easterly trade surge or two to tip us into another La Niña or a couple of strong WWB’s to quash the La Niña and rebound into a strong El Niño.
GFS has another incredibly strong trade wind burst coming up in a couple of weeks.
Not every agency thinks we are not in lanina atm. Recent flooding?
Yeah, looks and feels like an entrenched Nina worldwide despite the BoM claiming it has ended. And the consensus I've seen from those forecasters/mets/climos overseas is that La-Nina never really left to begin with.

The big Q I have is what happens to all that warm subsurface water during these big trade wind events? Some have said it will be upwelled to the surface but if that is really true then why are the mets all in agreement when they say that La-Nina will strengthen in the coming months? Or maybe they mean briefly strengthen before dissipating at the end of the year which will be when that warm water ends up surfacing? Dunno.
 

Craig B

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Warm water is already surfacing and will be drawn up more by this wind burst.

The difference in temps over the last month.

1657099642588.png


What happens from here on will be very interesting to watch. Do the westerly flowing surface currents upwell more of this warm water and spread it east?

Interesting to see the current CFS forecasts don't have the warm water signal that's already upwelled..

1657099788126.png
 
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Michael Hauber

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Surface temperature in far east Pacific is largely a combination of three factors - heating from the sun, evaporative cooling from the wind, and upwelling of cool water from below. There is also horizontal transfer of cooler water from the south from currents, but it takes a long time to move water a significant amount of distance (months to more than a year to cross the Pacific) and many people over estimate this factor.

If the subsurface is warm and upwelling is at average speed, then this upwelling warm water will cause surface cooling, but at a slower rate than normal. Therefore the balance between solar heating and subsurface cooling will tip in favor of solar heating and surface will warm. At the same time as average temperature is brought from below at average rates the subsurface warm anomalies will tend to ease.

If upwelling is fast enough then the cooling from faster upwelling may cancel out the reduced cooling from the subsurface water being warmer than normal and you still get surface cooling. Subsurface will tend to cool significantly as average temp water from below is moved up at a faster than normal rate.

If upwelling is slower than normal, then surface cooling from upwelling will weaken significantly further throwing the balance in favor of surface solar heating, and the surface will warm faster, and the subsurface may tend to warm as well as the rate of upwelling of cooler water from further down is reduced - this can only happen to a depth where solar radiation can provide heating, or if warmer water is available nearby to move in horizontally. Temperature gradients are stronger north to south than east to west so warmer water can move into the equator from north or south depending on currents/upwelling conditions.
 
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weathersourse

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Water along south America amon. Upwelling feeding cool water into the equator that eventually will be spreading across
3.4 with the trades surge. The pacific areas of interest both in the nth and south hem have high pressure driving trades across the cpac. https://apps.ecmwf.int/webapps/open...a-level-pressure:-weekly-mean-anomalies-87269 There are many things that should be looked @ ie high pressure and ridges and jet streams in the Northern hem. Until there is a reversal in the trades across 180 then it's just snooze time here for me.


sstaanim.gif


Anomalously cool water Chile to Argentina. Upwelling with ekman.
 
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weathersourse

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Cansips seasonal forecast for food for thoughts.

cansips-all-avg-pacwide-t2m_c_anom_season_mostrecent-1656633600-1661990400-1685577600-40.gif


It see's a cool anom flavour over our region well into mid next year. In a nutshell that a Nina flavour.

Kinda miss orebounds input on this thread he use to call things as they really are.


Anyways look back in again in few months. Good luck to all with their predictions however they pan-out or not.
 

Storm1

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Normally there is a lag isn't there between the atmosphere and ocean? The ocean should start to respond to the atmosphere shortly.
 
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weathersourse

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Normally there is a lag isn't there between the atmosphere and ocean? The ocean should start to respond to the atmosphere shortly.
Above its the other way around the atmosphere coupling is always the last thing needed to be declared in either phase.
SIO data supports it has not decoupled @ all.


Still be very weary myself of when we see another convectively coupled rossby kelvin-wave wave train forecast re: cfs plots passing over the maritime whilst the atmosphere is in this phase.


Screenshot_20220708_093829.jpg

Atmosphere is in the la-nina phase.
 

Mega

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The MJO keeps running into the Nina standing wave or 'brick wall'. I remember when we had that big pulse during January, there were many renowned mets (those we've quoted on here) who thought that would be the final nail in the coffin for this Nina but it clearly wasn't. Worth noting too that sourse was on the opposite end of the spectrum and wasn't convinced at all...looks like you were right.

I had a look at that NMME run last night, it's stronger again than either of its previous runs, and by a fair margin too.
 

weathersourse

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GFS has another incredibly strong trade wind burst coming up in a couple of weeks.

Yeah, looks and feels like an entrenched Nina worldwide despite the BoM claiming it has ended. And the consensus I've seen from those forecasters/mets/climos overseas is that La-Nina never really left to begin with.

The big Q I have is what happens to all that warm subsurface water during these big trade wind events? Some have said it will be upwelled to the surface but if that is really true then why are the mets all in agreement when they say that La-Nina will strengthen in the coming months? Or maybe they mean briefly strengthen before dissipating at the end of the year which will be when that warm water ends up surfacing? Dunno.
Good post this imo. The question (point you make). Who says big trade surge will upwell warm water to the surface?. It is the opposite to that moderate to strong trades upwell cool waters.

Screenshot_20220711_105025.jpg

Screenshot_20220711_105412.jpg

Just the very basics scheme of flow.
 

Michael Hauber

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Despite the current trade surge the east Pacific has continued to warm and is now firmly in neutral territory. Water near the dateline has cooled and is cool enough in my opinion to qualify for a modoki La Nina. Cool water in this region will help further trade wind surges but is no guarantee.

surface.png


I can see no possible explanation for the warming in the east other than a current downwelling wave, which is blocking the normal cooling effect of upwelling and allowing the sun to heat the surface.

subsurface.png


One thing that has puzzled me for a while is whether kelvin waves give rise to reflections. I have marked two possible reflections above. I often see patterns like this but am unsure whether the patterns are real, or just the natural tendency of the human brain to see patterns when things inevitably line up here or there due to coincidence.

The big issue is whether trade winds continue or not. Previous hints of a weakening of trade winds at the end of the forecast period went nowhere, and we have renewed hints of activity weakening at the end of both the current EC and GFS forecasts. Some weakening is probably inevitable and it may be short lived before a new strong burst, but if not then the currently definitely neutral SSTs in the east are not going to cool very much. Given the significant periods of weakened trade winds earlier this year with similarly cool SSTs further such episodes cannot be ruled out.
 

Long Road Home

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Despite the current trade surge the east Pacific has continued to warm and is now firmly in neutral territory. Water near the dateline has cooled and is cool enough in my opinion to qualify for a modoki La Nina. Cool water in this region will help further trade wind surges but is no guarantee.

surface.png


I can see no possible explanation for the warming in the east other than a current downwelling wave, which is blocking the normal cooling effect of upwelling and allowing the sun to heat the surface.

subsurface.png


One thing that has puzzled me for a while is whether kelvin waves give rise to reflections. I have marked two possible reflections above. I often see patterns like this but am unsure whether the patterns are real, or just the natural tendency of the human brain to see patterns when things inevitably line up here or there due to coincidence.

The big issue is whether trade winds continue or not. Previous hints of a weakening of trade winds at the end of the forecast period went nowhere, and we have renewed hints of activity weakening at the end of both the current EC and GFS forecasts. Some weakening is probably inevitable and it may be short lived before a new strong burst, but if not then the currently definitely neutral SSTs in the east are not going to cool very much. Given the significant periods of weakened trade winds earlier this year with similarly cool SSTs further such episodes cannot be ruled out.
If the amplitude were A = −50 cm/sec, so that the initial pulse elevates the thermocline, then nonlinearities decrease both the speed and zonal gradients across the pulse. Nonlinear effects such as these have been identified in numerical models and may contribute to discrepancies between observed and predicted Kelvin wave speeds.
Although observations that show eastward phase propagation along the equator are plentiful, it is difficult to find measurements that unambiguously show the presence of Kelvin waves. This is because the waves are superimposed on other waves and on time-dependent wind-driven currents (which have no dispersion relation) - ScienceDirect

Hopefully this clears some of that up.
 
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Long Road Home

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The big Q I have is what happens to all that warm subsurface water during these big trade wind events? Some have said it will be upwelled to the surface but if that is really true then why are the mets all in agreement when they say that La-Nina will strengthen in the coming months? Or maybe they mean briefly strengthen before dissipating at the end of the year which will be when that warm water ends up surfacing? Dunno.
It will make its way to the east Pacific. The decoupling still has to occur which takes months.
 
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Michael Hauber

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Some further observations on kelvin wave action, and differences between behaviour of warm and cool kelvin waves and associated el nino/la nina events.

Warm kelvin waves are easier to observe, and have the strongest impact at the far east. Here is an example of el nino development with the obvious presence of kelvin waves, and warming that starts on the eastern boundary and spreads west. At the same time direct warming occurs near the dateline and spreads east to merge with the kelvin wave induced warming in the east

el nino.png


In contrast here is an example of la nina development where cool kelvin waves are harder to differentiate. The subsurface impact is mostly central and has limited impact in the far east. Surface warming starts in the central east and spreads out in both directions. The spreading of cool waters to the east is associated with a strengthening of trade winds at the same time.


la nina.png



Other significant la ninas and el ninos show similar patterns.
 
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Long Road Home

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Keep in mind Kelvin waves, Sea height anomalies and wind anomalies are all different variables. I don't look too much into the models and obs due to the shear size of the Pacific hence less detail (much like isolated storm development along an east coast trough), the temp anomalies will always ebb and flow in both la nina and el nino.

What I'm looking at is the significant warm anomaly in the thermocline out west and then watch it progress east, which should be developing fairly soon.
 
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weathersourse

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Screenshot_20220711_142606.jpg





Below is just a example of when thresholds are met with a bonafide lanina modoki I used a bom example because that's
mostly all you guys look @ and take any notice off.
Example only not current. Used when there is warming on either side as show on last lower plot .






Screenshot_20220711_140626.jpg
Screenshot_20220711_142103.jpg

La nina modoki occurrences are indicated by cooling sst in central Pacific and warming sst in western and eastern equatorial pacific. Does plot1 sst in the post appear that way? to you.

JMA next enso update forecast should be out tomorrow.



May not be liked but above is the truth in ya face atm.
 
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Michael Hauber

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Just a quick question MH what cool modoki Nina thresholds being met are using to make your call.

Poor wording on my part as I didn't intend to say anything about formal declarations of anything. What I did want to highlight is that the nino 4 is cool enough to have a significant impact on atmospheric patterns. Latest weekly BOM is -0.51. Nino 4 temps have a lower variability, and absolute temps are much closer to the threshold of tropical convection at 28 C, so a lower change in temp will have a similar impact on tropical convection over that region to a change in temp over nino 3 or 3.4.
 

weathersourse

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Keep in mind Kelvin waves, Sea height anomalies and wind anomalies are all different variables. I don't look too much into the models and obs due to the shear size of the Pacific hence less detail (much like isolated storm development along an east coast trough), the temp anomalies will always ebb and flow in both la nina and el nino.

What I'm looking at is the significant warm anomaly in the thermocline out west and then watch it progress east, which should be developing fairly soon.
Myself think that boat sailed back in March when that kwave was disrupted by cooling. If you look back @ pentad you should see it quite easy. Myself look @ everything temps jets slp and sea heights over enso 3.4 is important.
 

Long Road Home

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Myself think that boat sailed back in March when that kwave was disrupted by cooling. If you look back @ pentad you should see it quite easy. Myself look @ everything temps jets slp and sea heights over enso 3.4 is important.
Yeah it's good to look at everything and also understanding why they all behave like they do. But not all changes in SST, Sea heights are due to Kelvin waves. It's only one variable in a more complex system.
For me the la nina continues until that build up likely creates a strong kelvin wave in months to come where the kelvin wave becomes a significant driver.
 
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weathersourse

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Sea height raises with warmer temps. Wespac is mostly always higher due to its warm temps. When Equatorial k/waves are generated in the kelvinwave generation area off eastern Indonesia it starts the downwelling rolling that moves across the eq.
Moderate to strong trades cause cause upwelling of cool water. In a nutshell if trades don't weaken or totally reverse @ the date line the cooler water will fracture the warmer thermo tongue of the west to east warming with it's upwelling.
So two engine's working against each other not in sync.
Everywhere in the world where there is warmer than average sst in any basin the sea heights are above regions of cooler temps. Expansion in a nutshell.


Definitely not trying to be a know-all just my 2cents.



Really nothing can be said. It's watch it play out and take notice of all official agency's updates on enso. Don't just go with blogs and social media posts. Have a look @ everything to do with la-nina in all regions not just our region.
 

Nature's Fury II

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In a nutshell if trades don't weaken or totally reverse @ the date line the cooler water will fracture the warmer thermo tongue of the west to east warming with it's upwelling.

Looks like this has just started happening already.

Check latest frames:

wkxzteq_anm.gif


If that upwelling strengthens and spreads, while the trades push the far eastern cold waters further west, you'll get basin-wide cool waters again and possibly quite rapidly. I can see why many of the models are going for a significant re-strengthening Nina.

Also, the extent to which the La Nina dissipates/western warm pool tracks east (as suggested by modelling during the summer) could well be critical in determining if eastern Aus gets another burst of flooding in the Jan-Apr period. Certainly would reduce the likelihood as the trade patterns and SSTs likely won't be as conducive to more dangerous events in that time frame.
 

Long Road Home

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Sea saw effect, after this burst of trades finishes, that downwelling out west has nowhere else to go but east - strong wave leading to strong el nino this time next year is my prediction. As for heavy rains and flooding in Eastern Aus, definitely potential for more into at least Feb due to the coupling of the atmosphere
 

Nature's Fury II

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Sea saw effect, after this burst of trades finishes, that downwelling out west has nowhere else to go but east - strong wave leading to strong el nino this time next year is my prediction. As for heavy rains and flooding in Eastern Aus, definitely potential for more into at least Feb due to the coupling of the atmosphere
Yes, the potential El Nino to come could be quite horrendous. One wonders if we're in for a spell of dry years ahead much like we saw in the back half of the 2010s after the double Nina.
 

Storm1

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Didn't the Millienum Drought start after the 1998/2001 La Nina? Perhaps we could be looking at something similar after this La Nina winds up.
 
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Locke

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Sea saw effect, after this burst of trades finishes, that downwelling out west has nowhere else to go but east - strong wave leading to strong el nino this time next year is my prediction. As for heavy rains and flooding in Eastern Aus, definitely potential for more into at least Feb due to the coupling of the atmosphere

But looking back, previous multi-yeat La Nina's haven't imediately been followed by strong El-Nino's.
 
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Long Road Home

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But looking back, previous multi-yeat La Nina's haven't imediately been followed by strong El-Nino's.
Its not unusual to have a slower reversal however due to this year being an unusually prolonged strong trade wind burst, my gut says it will reverse strongly. Could be wrong, but next 3 months or so will tell the story
 
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Naturestorms91

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El Niño followed in 2002 after the 1998/2001 La Nina.
Yep I was thinking about that before headed to this thread! So much coincidence. The 2002 El Nino was incredibly strong and severe despite after 3 years of La Nina. The year of 2000 was very cold especially in the winter like 2022 experiencing now.

2001 brought last hurrah of floods in early of the year before switch to dry in middle of the year that lead to El Nino conditions and positive IOD. 2001/2002 summer saw bushfires started before eased in late 2003. So definitely 2023 will be similar to 2001.
 

PeteJ

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Wasn’t it also up to about 2006‘ish that the dwindling dams in SE QLD were BIG news until it started to get wetter around 2007-2008.
 

Craig B

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Another thing that 2019 we had was incredibly dry as well. It like a role reversal to 2002. In between triple La Ninas.
That was linked to one of the strongest + Indian Ocean Dipole events on record, and then the Stratospheric Warming Event, and resultant + Southern Annular Mode into summer.

2002 was the only previous known Stratospheric Warming Event for the Southern Hemi.
 
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