Are we heading for a double-dip La Niña?
TL;DR
- El Niño events generally return to neutral the following year, unlike La Niña which has a 50% of returning back to La Niña
- This is called a double-dip La Niña
- A recent burst of west-flowing surface currents may be the catalyst for a double-dip La Niña
- The prediction is bolstered by a developing negative Indian Ocean Dipole event - which usually coincides with La Niña
- La Niña brings moisture to Australia, plus increased swell for the East Coast but a decrease in the southern states
The chances of back to back La Niña events (know as a double-dip La Niña) into the 2021/22 summer have just increased slightly.
This is great news for East Coast surfers though not what Victorian and South Australian surfers want to hear, especially with the last event being so fresh in their memories.
Before we get stuck in, it's worth noting that El Niño and La Niña don't swing back and forth like a pendulum, and that there's even a neutral phase between the two.
Historically, once a La Niña event has run its course the chances of back to back La Niña events is 50%, yet the same isn't true for El Niño. The reasoning behind this is explained in more detail below, but as we move through winter we're starting to see a few signals which are favouring a double-dip Niña event.
El Niño and La Niña events aren't symmetrical. Meaning they don't mirror each other from one side of the Pacific Ocean to the other.
We know that during La Niña events, warm water piles up in the western Pacific Ocean, bringing increased convection and moisture to the Australian region, with cooler waters upwelled to the east. El Niño is the opposite with warm water to the east, and cooler towards us in the western Pacific Ocean, leading to subdued convection and less moisture for our region.
Where the peak of this cool/warm (La Niña/El Niño) water anomaly sits across the Pacific varies between the two phases, and this is where the symmetry falls apart. La Niña's see the cold pool developing further west than where the warmer El Niño pool sits, which is further east (shown below). If all were equal we'd see the same region of ocean cycling between cold/warm events but they're slightly offset.
Also El Niño's are generally stronger regarding the shift in surface temperature from normal. That being the warm water anomaly for the ten strongest El Niño's is larger than the cool water anomaly.
The asymmetry between El Niño/La Niña events. Peak in temperature is in a different region, and El Niño's are stronger
So if the shift in sea surface temperature is larger for El Niño, then why don't we see back to back El Niño events compared to the relatively weaker La Niña signal?
The answer is in the strength of the feedback loop. During warmer water El Niño events, heat is released into the upper atmosphere and flows back to the poles. This feedback system is much greater than La Niña's helping it reset to neutral more quickly. La Niña's instead see a slower return to neutral and this in turn slightly primes the ocean and atmosphere for another La Niña event to kick back in the following year.
This phenomena is shown in the graph below which plots the change in sea surface temperatures across the Niño 3.4 sector (central) equatorial Pacific Ocean.
Every first year El Niño/La Niña is plotted from 1950 (left), with the following year's developments to the right.
Sea surface temperature anomalies for the Niño 3.4 region for all first year El Niño events (top) and La Niña events (bottom) and the following year. The statistical significant double-dip La Niña can be clearly seen
What these statistics show us is that during the year following an El Niño, conditions, on average, return to neutral and sea surface temperatures back to normal.
However, following first year La Niña events, conditions have a tendency to stay on the La Niña side, though on average not as intense as the previous year's event. This is known as a double-dip La Niña and statistically it's a 50% chance following the first year of La Niña.
Knowing this, we've been keenly observing events in the central Pacific Ocean regarding any sign of a double-dip La Niña, and in the past fortnight we've seen a few indications that increase the chance slightly above 50%.
Firstly, Kathleen Dohan from Earth and Space Research has done amazing work correlating surface current changes across the equatorial Pacific to the evolution of a La Niño/Niña event.
After filtering out seasonal differences, a clear signal appears which shows that following a westward surface current anomaly (flowing to the west and shown when the blue line dips negative) we see a shift in the Sea Surface Temperature (SST) anomaly the opposite way shortly after. This shift is positive (red line going positive). La Niña events are shown when the red SST line pushes above 1 standard deviation and El Niño events when it dips below -1.
This correlation plays out beautifully and you can clearly see last year's La Niña develop after the surface current dipped towards 2 standard deviations and the SST accordingly rose above 1 standard deviation.
First EOF modes of sea surface current anomaly (blue - positive = easward current) plotted and sea suface temperature anomlay (red). Source: Earth & Space Research
Looking at the past two decades, the strong 1997/98 El Niño clearly stands out, as well as 2010-12 La Niña and 2015/16 El Niño.
First EOF modes of sea surface current anomaly (blue - positive = easward current) plotted and sea suface temperature anomlay (red). Source: Earth & Space Research
This analysis gives us a slight heads up on a possible developing El Niño/La Niña event by monitoring the surface current changes from normal.
So coming back to recent observations, we can see SST (red line) is still returning slowly to neutral following last summers La Niña but with the recent westward surface current anomaly (negative dip in blue line) we can expect those surface temperatures to head back north over the coming weeks, towards La Niña thresholds.
This appears to further increase the chances for a double-dip La Niña. We also have a developing negative Indian Ocean Dipole event in the Indian Ocean (warm water off Indonesia, cooler towards Africa) and this usually goes hand in hand with La Niña.
As for swell, another La Niña would see a summer and autumn similar to the one just gone. It's a plus for those on the East Coast with an increase in swell energy from the east along with winds from the south-east to east, while a shift in the storm track further south brings less swell to the southern states and unfavourable south to south-east winds.
NOAA's Climate Prediction Centre has the chance of La Niña reforming at just over 50% this November/December/January in its latest update so we'll continue to keep a close eye on the developments throughout the Pacific Ocean over the coming months.
Comments
FFS Craig. I just went and bought some cool water wax. Lift your game!
Yes, that is an attempt at humour.
Surfing aside, I'm glad I'm selling my house because it was far too wet for me this year. Crazy amounts of rain like I've never seen and I thought it might be a few more years of drought until we have another onslaught like this 2020/2021. Mother Nature is pissed and she's just warming up (pun not intended)!
Blergh, add another 6 months onto my deck getting done.
Fantastic work Craig. Thanks for sharing your very impressive knowledge. A bit of a modern day prophet, ha. This is why I am a Swellnet subscriber.
Great article, Craig.
Poor fellow, my southern coastline.
Go East
There's waves in LaNina time,
Go East
Away from onshore slime,
Go East
Except maybe not to Sydney,
Go East
In LaNina where I'd rather be!
Sounds like you started lunch nice and early, VJ.....
I wont say no to another bout of La Nina. Nothing worse than a summer of relentless devil winds.
Very interesting. Another La Nina summer would be extremely helpful after the extreme heat and drought eastern Australia endured for several years up until about 15 months ago.
Can I have my donation back farmers?
Or have the mice eaten it?
Great article Craig, cheers.
I always thought a La Nina followed an El Nino but that appears not to be the case. Looking at the average sea temp anomaly for 3.4 region graphs above, it looks like El Nino Vs La Nina temp anomaly is about the same for each, but for the ten strongest its not, well it also looks like there is only about 10 La Nina in that graph vs maybe 20 El Nino's, with a ~50% double dip rate you would probably expect to see more la Nina's recorded, but maybe I am interpreting the graphs incorrectly.
Craig wrote :
"Also El Niño's are generally stronger regarding the shift in surface temperature from normal. That being the warm water anomaly for the ten strongest El Niño's is larger than the cool water anomaly."
Thanks guys,
JY, regarding the first point, the top ten strongest El Niño's are between 2.25 and 2.75 degrees C above normal, while the top ten La Niña's are only up to 2.25 degrees C below normal.
The second graph shows all first year events, weak to strong from 1950, and as El Niño's are more common than La Niña's that's why there are more lines/events shown for El Niño's compared to La Niña's.
Quote Craig- "As for swell, another La Niña would see a summer and autumn similar to the one just gone. It's a plus for those on the East Coast with an increase in swell energy from the east along with winds from the south-east to east, while a shift in the storm track further south brings less swell to the southern states and unfavourable south to south-east winds."
So NW Australia and mid west Australia will see another rarely surfable summer?
Even the magnets didnt get much swell untill about march even then small.
Waters still warm here but at the moment morning temps (air) have been around 2' - 6'C Too cold for me thanks.
Jeez it must be cold in the desert with these cold easterlies.
Yeah would expect similar if it develops but we'll see how things play out.
thanks Craig..will have to start fishing then.
"The chances of back to back La Niña events (know as a double-dip La Niña) into the 2021/22 summer have just increased slightly."
I remain somewhat sceptical and reckon "slightly" is the operative word.
Great article, though. Cheers, Craig!
"not what Victorian and South Australian surfers want to hear, especially with the last event being so fresh in their memories."
........and Covid life. Hopefully not.
Thanks Craig, great writing and forecasting.
My arms are cooked after last summer/autumn.
Thanks for this article Craig,
Great info as usual although these types of analysis do make my head hurt a little. Part of me wants to just skim it and get the takeaway while the pedantic part makes me delve into the details and understand what's going on. So thanks I think.
Living in Wellington NZ El Nino/lLa Nina seems to have a pretty ambivalent impact on our surf prospects, it seems to depend a lot on the unique characteristics of each event.
Really strong El Nino has at times had a diabolical impact on our south swells with just too much of a westerly driver, but not always.
Good article Craig.
Bring back the drought I say.
Great read Craig.. thanks again, hopefully it plays out that way, not just for the waves but the farmering industry etc .. cheers
Looks like the beer gut is gonna get bigger.
F#$K OFF La Nina!
NOAA have just issued a La Niña watch.. https://www.climate.gov/news-features/blogs/enso/july-2021-enso-update-la-ni%C3%B1a-watch
"As things stand with the El Niño-Southern Oscillation (ENSO), neutral conditions are currently present in the tropical Pacific and favored to last through the North American summer and into the fall. But forecasters at NOAA’s Climate Prediction Center have issued a La Niña Watch, which means they see La Niña likely emerging (~55%) during the September-November period and lasting through winter."
So maybe my shoulder surgery will be full healed once it lifts.
We're seeing more consensus between global climate models and government agencies regarding the increasing likelihood of a double-dip Niña event, and the latest data from Earth and Space Research also consolidates this. https://www.esr.org/data-products/monthly-enso-index/
We've had a further negative dip in the surface current anomalies (blue line), ie westward flowing surface currents from bursts of easterly trade-winds.
We then look to the red line (sea surface temperature anomalies) to jump back up in response and there's a tiny inflection on the graph here. Watch this space over the next few weeks.
We're seeing sub-surface (below surface) cool water temperature anomalies strengthening and nearing the surface over in the eastern Pacific Ocean. This will help feed any developing La Niña and won't take much of an easterly burst to upwell to the surface.
This is a cross section of the equatorial Pacific Ocean showing the water column from surface down to 450m depth..
oh facepalm
And here we go, that purple blob forecast from the 24-26th July is easterly wind anomalies over the eastern Pacific. Negative in value as we're looking at zonal (westerly winds) here, so + equates to an increase in the westerlies, while - equates to easterly winds.
Could be the final catalyst to kick off events..
Pretty tidy trade burst in the Nino 3.4 area right now Craig.
I'm starting to come on line to this bullish outlook for a double-dip.
Welcome aboard the double-dip Niña train Steve!
The dream continues…..double dip La Nina lockdown
Great read. Thanks.
BOMs already calling the negative IOD.
https://www.abc.net.au/news/2021-07-20/bom-declares-negative-indian-ocea...
And for what it's worth, it's pissing down here, has been for days, and no end in sight. Can't wait for another summer of howling South Easterlies on the south coast. :(
Could be an interesting rainfall outlook for the next 12 months as the Indian Ocean is already in a negative IOD condition.
https://www.abc.net.au/news/2021-07-20/bom-declares-negative-indian-ocea...
the observations here are of constant cloud bands from the west.
classic neg IOD signal.
Classic north-west in-feed here (yesterday morning)..
yep.
Interesting to listen to the daily Met wrap-up on the ABC rural report and hear the talk about rainfall on the western slopes of the ranges.
while we get the cloud but are in the rain shadow of the prevailing systems.
Here comes the upwelling.
Looks like we're certainly heading towards another La Niña looking at the evolution of the SST's across the equator over the past month..
The final image zoomed in..
New Zealand's NIWA (National Institute of Water and Atmospheric Research) has just gone into La Niña watch, in line with NOAA. Waiting for the BOM over the coming weeks.
I was skeptical after last year did not see the intensity of La Nina i was expecting ( yeah i'm focused on North and West Victorian Precip influence as opposed to Surf ) . Since i saw the breakdown of NW infeeds around July last year the summer didn't matter as much . Obviously the surf influence ( and Qld-NSW coastalfringe Precips were very visual and well documented .
Of interest i think that the Nth Hem influence initiated a ENSO teleconnection to the IOD and out of nowhere this cool subsurface pool looks like its going to supercharge things even more .
Even when NOAA announced a potential La Nina watch i wasn't even focused and was too interested in the IOD .
Funnily enough the recent dry/winter season rains in SE Qld were a tell tale that i was looking more at the Indian as the primary influence . But the Atmosphere is saturated , with water vapour being advected on all fronts .
God help people in low lying areas come storm season . This has the potential to outstrip 2010/2011 .
Usually the standard 18 mth cycle of La Nina is a fair bet . But looking at this now we are looking down the barrel of 54-56 or worst still 73-75 .
This is highly unusual but the SW land division ( SWA ) is usually bone dry during La Nina . Which re interates that the IOD has been triggered by the ENSO and will now bounce back to the East in its influence in Australia as the Negative IOD peaks and then the La Nina starts bearing its teeth come Oct .
Update:
Things are continuing to slowly bubble away with cool sea surface temperature anomalies setup through the central Pacific from anomalous easterly trade winds, warmer to the west.
The big key to the coming double-dip Niña is the sub-surface temperatures. They're cooler than normal and waiting to be upwelled with the next burst of easterly trades, which looks to occur over the coming week.
Here's the forecast wind anomalies at 1500m above the surface at the equator, showing we've got good easterly trades on the way (dark blue box) through the central and western Pacific which should help upwell that cooler water. Blue = stronger than normal east winds, red = west winds.
And finally NOAA is going a 70% (upgraded from 66%) chance of La Niña conditions through their winter, our summer.
Devastated. The water is beautiful right now. It’s a shame to take a retro step towards cold water again. The La Niña rains will be very welcome though.
Thanks for the update Craig.
Aren't they, took these shots last week, as good as it gets!
That is as good as it gets.
First swim in boardies for several months today. Wisteria budding up. Baby birds everywhere. The return of cold water will suck but the associated East swell is very anticipated.
Blowin, I think La Nina would be better for water temperature, but more rain would make the water more turbid.
It is the El Niño i.e a drought year, when you get relentless nor’easters and lots of cold dirty water upwellings plus the associated red weed, corn flakes etc
Edit: on north coast NSW anyway
Yep agree.
Cheers Distracted.
El Niño years sound like crap.
yep. La Nina is warm water.
local SST's gone back up to 21 after dipping to 19.
felt warmer today.
huge bait ball been hanging around the last few days.
Saw one guy surfing the back bank on his own right in the middle of it.
I don't want to jinx it but doesn't seem as many anecdotal GWS sightings as last year. Thoughts?
The Australian Bureau will update their climate driver outlook today. I wonder if they'll go on La Niña watch? http://www.bom.gov.au/climate/enso/outlook/
NOAA forecast models have strengthened a little, pointing to SST anomalies in the important Nino 3.4 region being about -1 below average into the end of the year. This is the threshold for La Niña.
Also the negative zonal (meaning easterly) wind forecast anomalies are expected to broaden across the Pacific into that 3.4 region (blue and purple shading).
This should lead to further upwelling of cool sub-surface temperatures, and really get things turning over. If this goes to forecast it looks like we'll be well under way into the middle of September..
Also as Steve has mentioned in his Forecaster Notes, the current setup developing for the East Coast looks like a classic Niña signal.
Interesting that despite the La Niña signals and the moisture being directed towards the east coast from the Tasman, it is relatively dry on the coast. Next week after the front passes on the weekend looks like a big high pressure system setting up over the mainland which will continue to keep things dry.
Well the La Niña hasn't developed yet, but it feels like there are signals out there in the synoptics.
Also, the IOD hasn't really played a part since July across the south-east of the country either..
We've just recorded the 4th warmest winter on record as well as a nation.
I certainly hear you Distracted - it looks green and healthy here, but the reality is the ground is quite dry. La Nina never hit here last year, missed most of SEQ I reckon aside from those coastal parts particularly around Gold Coast and hinterland. Venture a little inland and nothing much really, here just managed to achieve around average rainfall, on top of successive years of below average. So I feel we've still got a deficit going on.
just heard on ABC radio this morning that SEQ's main dam is at the lowest level in many years, and water restrictions will kick in by December if nothing changes. I'm hopeful if we get another La Nina this year it will shift its focus to these parts. Any evidence to support that hope Craig?
Yeah last Niña kinda skunked SE Qld hopefully this ones hits a bit better.
This looks to be the final trigger to set off this coming La Niña.
Those purple easterly wind anomalies (forecast into the middle of the month) should be the final kick to set things in motion proper. Though positioned a touch further west than ideal all the precursors are there ie cool sub-surface water.
Hi Craig,
This BOM link below is suggesting a fairly mild La Nina, which I think is what you've hinted. Is your sense it's unlikely to be as strong as last summer's?
http://www.bom.gov.au/climate/enso/#tabs=Pacific-Ocean
Yeah at least moderate. The latest NCEP modelling has it being nearly as strong as last seasons regarding the SST anomaly departure from normal. Usually the second is weaker than the first though.
Great, thanks Craig.
Great work Craig .
What are the chances of having a similar surf season as this year ?
Do I need to try and get to the East coast around May/June ?
Earlier if it comes off Hutchy, late summer and autumn.
Thanks Craig . Also thanks for posting that audio re the IPCC models . I learnt a lot ( have also done some additional research ) and now question my previous view re CO2 having no influence . I will do more work .
Saw a video on the huge warming period 55-60 million years ago . Went into detail of Ice Ages cycles and warm periods ie the big influences . It showed that smaller cycles could happen ( this one was 300000 years ) and their theory was CO2 changes . They were not sure what caused it though .
What we have here is a strong burst of anomalous easterly trade winds forecast along the equatorial Pacific and all important Nìno 3.4 region over the coming week (blue purple colours). Forecast runs from the black line downwards.
This looks to be the final trigger to kick of the coming La Nìna this summer. NOAA model forecasts have the threshold of -1 being easily met (second image) over the coming months. Bring it on.
Also those wanting to know how that sea surface current indicator is going, it's on the way back up (red line) owing to stronger, westward flowing currents from the easterly trade-winds..
NOAA now have a 70-80% chance of La Nìna developing through Nov/Dec/Jan.
The Bureau are finally coming to the party..
Craig was there a stage earlier in the year that you were calling the La Niña more for now (our spring)? Has this been pushed back a little?
Nah, they're always in summer, but the developing stages should hopefully have an effect on our spring and bring less of those northerlies like last year.
Thanks for the clarification mate. Probably just wishful thinking on my part. But glad it may limit the damage this spring if comes off!
Last Spring was great.
September is traditionally the driest month here and we may have to get through a bit of Spring before any moisture eventuates.
Looks like some drying winds ahead.
Yep looking like another one with plenty of trade-swell and winds more from the south-eastern quadrant.
Here's the long-range probability maps regarding Mean Sea Level pressure being higher/lower than the norm and what we can see is a favourable setup for the months Oct/Nov/Dec..
Even better and juicier for Nov/Jan/Dec with that cradling high and low pressure anomaly dip.
Update:
The Niño 3.4 index is plummeting from all that anomalous easterly trade-wind activity along the Equator.
Interestingly looking at the position of the cool water anomalies, they're quite far west which puts it in the La Niña Modoki category.
Modoki's usually see the rainfall across Australia more focussed towards the west, ie away from the East Coast and more towards central Australia, the NT and north-east WA.
Looking at the cool sea surface temperatures off south-east Qld this looks to correlate as well.
Rainfall correlation across Australia with La Niña Modoki left and traditional La Niña right (blue = rainfall increase)..
Craig ."Rainfall correlation across Australia with La Niña Modoki left and traditional La Niña right (blue = rainfall increase).."
Modoki is a term I am not familiar with .
Modoki is a La Niña/El Niño that is positioned further west compared to a normal Niña/Niño.
IE the signal across the Equatorial Pacific is shifted more west, hence the impacts to Australia are also shifted. For a La Niña it shifts the increase in rainfall from what would normally be the east, more to the west and central/northern Australia.
Nice one Craigos thanks for keeping us updated on this.
Do we have any idea of how the Modoki La Nina affects surf prospects? More close range E swell hugging the coast or can we expect more welcome Trough Blocks™
It would but not sure how. I'm constantly keeping an eye on the long-term outlooks and indicators.
Looking at the SST signature we might be looking at more long-range energy from south of Fiji, but in the Tasman Sea it's hard to say. It looks like less TC's in the Coral Sea immediately off Qld and an increase in activity off NW WA, the NT and around Fiji/Tonga/Samoa.
Nice one. Will be interesting to see how it unfolds. Hopefully it pans out nicely with regional travel back on the cards soon.
"more long-range energy from south of Fiji"
"less TC's in the Coral Sea immediately off Qld"
Beautiful!
The West of the US has experienced drought with this La Nina . Would the Modoki bring in the rain that fell this year in the Gulf of Mexico ?
Thanks for keeping us up to date on these important long term effects on our surf !
Here you go Hutchy, here are the latest outlooks for the US from Oct/Nov/Dec..
I hope I'm wrong, but that rain forecast looks suspiciously like dreaded northerlies for SEQ & NNSW
Thanks Craig . You are definitely an on the ball expert on the possible long term implications .
I was wondering about the effects next year with the Modoki on the west of USA . Will the jump to the west mean that the South West of US get more rainfall like the Gulf got this year ? Will it break the terrible drought they are now experiencing ?
Probably not would be my uninformed guess .
Ah sorry, here is a good, quick read comparing to past Modoki events, and no, only to the north-west there's an increase in rainfall, and across Mexico and Central America..
https://climateimpactcompany.com/daily-feature-la-nina-modoki-risk-later...
Oct-Dec
Gosh - what a font of information you are . Much appreciated .
Agreed, thanks Craig.
In addition to enjoying La Nina for great summer surf potential, I'm also hoping it eventuates because:
- I just planted our garden out
- it's f@cken stressful living down here south of the Royal NP when it's a dry summer (bushfires)
- looks like NW USA could get a good snow season and that's where I'd head if i could (sans family)
La Nina alert: http://www.bom.gov.au/climate/enso/outlook/
Yep, here's the latest update: https://www.swellnet.com/news/swellnet-analysis/2021/10/12/double-dippin...
thanks Craig