Recapping Our Double-Dip La Niña
La Niña.
At the very least, Swellnet readers should have learnt this tiny portion of Spanish over the past two years. Whether for the better or for the worst, most have felt the effects of back to back La Niña events across the country.
It's Spanish for 'the little girl', though it could well be the 'bearer of rain'.
The onset of the first La Niña saw pumping surf right across the East Coast just as the pandemic and lockdowns kicked off in earnest, way back in March 2020. In NSW, autumn and winter of 2020 were some of the most consistent and best seasons in recent memory, while relentless easterly swell provided non-stop surf further north in south-east Queensland throughout the autumn and summer of 2020/21.
That summer, drought-breaking rains turned tinder-dry rainforests back to glistening green wonderlands while also restoring soil moisture after record lows during the summer of 2019/20.
As we moved into autumn last year it became clear that we were in for back to back La Niña events - otherwise known as a double-dip.
Mid-latitude systems dominated the southern coasts of Western Australia, South Australia, Victoria, and Tasmania, while the East Coast continued to receive swell after swell.
Spring finally sprung, temporarily, across the East Coast through November and December last year with a run of strong northerly winds, but the tropical switch was flicked back on around Christmas with endless pulses of easterly swell energy and increasing rainfall totals across most of the Eastern Seaboard.
It also brought more favourable winds, with persistent coastal troughs and instability leading to variable winds across southern NSW, helped by weaker sea breezes due to the warmer sea surface temperatures flowing down the East Australian Current, while protected points faired best in northern NSW and south-east Queensland.
On the other end of the scale was Victoria and South Australia, discussed in more detail below.
Classic La Niña setup with cooler water in the central and eastern Pacific Ocean with warmer water to the west, flanking Australia and Indonesia
The catalyst for the increased rain and easterly swell is a build up of warm water around the north of Australia, created by stronger than normal easterly trade winds through the equatorial Pacific Ocean. Warmer water leads to increased convection (read moist, rising air), instability, and storms.
The increased instability and low pressure generated by this warmer water shifts the sub-tropical high pressure belt further south, exposing the East Coast to a moist onshore flow. What this does for the southern states is put a big block across the Southern Ocean, denying swell for the coasts that rely on it.
This can be seen clearly in the image below which depicts the Mean Sea Level Pressure (MSLP) anomaly for the summer just gone. That being the difference in surface pressure from the long term climate average, with red showing higher than normal pressure and blue/purple, lower than normal pressure.
Mean Sea Level Pressure (MSLP) anomaly for the summer just past
It also brings unfavourable winds from the south-eastern quadrant, but with the extra instability that La Niña produces inland across the country, winds have actually been more east across Victoria and South Australia. It's just the lack of quality swell that's been the main issue.
The blocking setup has kept Western Australia subdued as well. The South West has seen plenty of offshore days but with smaller swells, while the suppressed Southern Ocean activity isn't ideal for Perth and Mandurah which need an active westerly storm track to get going.
Also, persistent heat troughs forming inland were responsible for gusty offshore winds which brought in hot air from the desert and saw Perth register its hottest summer on record.
In Tasmania, the shift of the westerly storm track south is actually favourable as any polar frontal activity sits more ideally in its swell window. They were let down by flukey local winds, although the East Coast benefited from all the swell activity in the Tasman and Coral Seas.
Below I've attached the relative humidity anomaly chart for last summer, just to highlight how much wetter and humid it's been. Inland New South Wales tells the story, with the high rainfall totals contributing to a more humid and cooler summer - in terms of maximum temperatures - with this also spreading across most of the eastern seaboard.
Relative Humidity (%) anomaly for the summer just past
Looking at the surface wind anomaly chart, we can see the stronger than normal winds out of the south-east through the Tasman Sea and north of New Zealand as well as the easterly winds across southern Australia and south-west Western Australia.
Surface wind anomaly for the summer just past
The big question is how long the current La Niña will influence the weather and surf around Australia.
In short, its effects on rainfall look set to linger through autumn and into early winter with a wetter than average outlook forecast for most of the country by the Bureau of Meteorology (BOM) and European Centre for Medium Range Forecasts (ECMWF).
Surf wise, it looks like the blocking setup across the Southern Ocean will start to break down over the coming weeks bringing more swell-producing systems for the southern states, but winds look to be dominated by mid-latitude troughs and lows. This may initially spoil the swells into the end of the month, but we'll continue to provide more in depth analysis in the Forecaster Notes.
As for the outlook for next summer, most long-term seasonal models have us returning to neutral (neither La Niña or El Niño), but the model I've been monitoring and using over the past two summers has a third La Niña developing. A third La Niña would be a trifecta that hasn't occurred since the 1970's.
Keep an eye on the site through the coming months for more on this.
Comments
Wouldn’t mind some westerly winds to go with these easterly swells in nsw
wouldn't mind a surf
What he said...
Fucken oath, The belt has expanded, while shoulders and gonads have shrunk.
A triple dip.....aaarrggggghh.
Nice one Craig, those EC low pressure anomaly prog charts you posted right at the start of the season turned out to be right on the money too.
Didn't it..
Here's the forecasts for summer from UK Met and ECMWF, generated back in October.
UK Met Dec/Jan/Feb forecast:
ECMWF forecast:
And observed (as in article above):
Very good read Craig
Great article Craig ,,,,,whats scary is a the opposite of whats happening now and thats dry /drought conditions because of the unprecedented growth in the bush at the moment,, certainly a land of contrasts .
yep - pretty scary scenario we will be faced with soon enough. I know its bloody wet but I can almost smell the smoke.
worst SA summer since 2007.
As always, a fantastic insight and wrap up, thanks Craig I really get a lot out of these articles you produce. Be good if you shared them to mainstream sites as well so the average punter could understand about how the weather is actually behaving. But of course we all know it's a government conspiracy, hey-lol
Thanks Dave!
When the weather gets dragged into conspiracy circles, you know we're doomed ;p
Good read and explanation. Cheers!
Fantastic write up Craig, thanks mate but geez I hope you're wrong re a third La Nina next summer! That would suuuuck!
More to the point what is winter doing sounds like a shocker for the west vic coast the lack to NW and average or below swell. Could be alright for the east though, a whole week of surf last week, crook this week though. Any idea what the forecast in Cabo san Lucas is for the next few weeks Craig? Have a holiday booked.
I know it equates to swell but I reckon I’d be happy if the triple dip didn’t happen next summer.
Good read - maybe some of our leaders will read it too !
A 3rd La Niña will validate my decision to start kite boarding this summer…best we have an alternative
A triple dip could be scary. Observing the last couple of double dip events, the second summer of La Niña in a row seems to have more precipitation than the first. Be interesting to see all the data from double dip summers. If it is the case, could a third be wetter than the second year?
Anyway of digging up this data Craig?
The house my grandmother grew up in Coraki has been in the family for 100 years, never had water in it until this flood. 1.2m above the floor boards. Grandma had a print out of all the floods/heights from 1877 to mid 1990’s for Lismore and towns along the Richmond. 1880 being the biggest until 2022. Were some patterns in the data, where there were 3 - 5 year bursts of lots of major floods. 50’s and 70’s etc.
Some interesting history there. Craihg maybe you could look at 50's and 70's La-Nina/El Nino charts to see what was happening back then with back to back floods.
These charts are a great resource for a quick overview of the years and the difference in rainfall (deciles) from the climate average.. http://www.bom.gov.au/climate/history/rainfall/
Cool poster. You can see a couple of triple dips in there. :(
That Climate History link is very interesting. Comparing '74 and the damage done to local beachfronts back then and its associated "highest on record" rainfall. Another triple dip year from memory?
Yeah 73-76 was the only triple dip recorded regarding the current records.
Correction, 98-01 was a triple as well.
wow
Hey Craig, does el nino years have opposite affects on swell for southern states and east coasts. ( more swell southern ocean less east coast)
I did this article nearly seven years ago.. https://www.swellnet.com/news/swellnet-analysis/2015/08/05/el-nino-and-a...
Re-doing it now I'd have a much greater idea on the impacts for Australia surf though.
It's not quite opposite but the dominant swell direction across the East Coast swings from more easterly (associated with La Niña) to the south and that's owing to the more active Southern Ocean south-west of Victoria. So yes.
Craig, as you wrote previously, with double-dip El Ninos, the second dip is usually weaker than the first. Obviously, we have received more rainfall on the east coast with this second dip. You have probably covered this previously, but has the temp difference between the east and the west Pacific been bigger during this second dip when compared to dip one?
Across all the indicators in the Pacific Ocean, this year's was a touch weaker but across Australia we certainly did see more rainfall so while the second is usually a touch weaker this doesn't equate to less rainfall in our region as it's been shown.
Oceanic Niño Index (ONI) index
Nino 3.4 region anomaly..
Raw data here and you can zoom in on those charts, just grab with the cursor. https://www.ncdc.noaa.gov/teleconnections/enso/sst
Reckon the pressure anomalies were probably the key for this summer being wetter than last despite the weaker La Nina this year. I've been looking at MSLP charts for some 30years and I don't think I've ever seen H pressure systems centred at 50 degrees latitude or the monsoon trough consistently form a huge arc from the tropics down the East Coast which was so often the case this summer.
I think SAM was for the most part positive or neutral this summer (as would be expected with the persistent higher than average pressure in the Southern Ocean to the south of Australia), and it appeared that this contributed to allowing the monsoon trough to stay planted further south.
I wonder if perhaps the tightening pressure gradient as a result of Antartica being comparatively colder than the mid latitudes as the planet warms could be a contributor in exacerbating the severity of tropical climate drivers. The extreme positive IOD of 2019-2020 comes to mind as example of a driver that could be made all the more severe in combination with an increased frequency of a neutral/positive SAM.
Makes me think that as we increasingly upset the energy balance of the ocean/atmosphere system, it would seem all the more likely that known climate drivers will become more powerful through various positive feedbacks. Perhaps our understanding of what the probable effects of a weak/strong La Nina/El Nino/IOD, will have to change in time.
SDW or Craig, can you post up a chart of the H pressure system at 50 degrees south?
Are we seeing more meriodonal ridges and troughs? like the NHemi seeing the crazy meriodonal swings - eg that snow in Texas event.
Here it is, the MSLP anomaly for summer, and can see that big block at 50s..
And in regards to large swings in weather like in the NH, that's due to the polar vortex and it's strength.
We don't see as big oscillations across the SH due to the greater ocean landscape and lack of continental influences as seen throughout the NH.
Agreed.
I think the moisture transport between the west pacific warm pool and East Coast was greater this summer, due to the strength of the sub-tropical high pressure belt/ Hadley circulation.
And the amount of troughiness that this warm, moist air was feeding into was extreme.
I don't think models were quite able to resolve the sheer amount of water vapour being transported in a super-saturated atmosphere.
Whilst I absolutely detest this La Niña weather pattern, I really enjoy the way you explain it all Craig so I can understand it. Helps ease my agony as a west coast vic surfer
Thanks Craig, awesome stuff!
Bring on the triple dip, but hold the sky rivers please.
I've just had a shoulder reconstruction that has me out of the water for 12 months, so I'll be able to rack up the froth for my return next year!
“As we moved into autumn last year it became clear that we were in for back to back La Niña events - otherwise known as a double-dip.”
Hey Craig, your clarifications have confused me a little. I thought that La Niña and El Niño were largely summer phenomena for us (September to March) before they break down, and that even with this double dip the BOM doesn’t ‘call it’ until late winter to early Spring, while giving indications of likelihoods in their forecasts.
You seem to be suggesting that this third dip is possible based on readings now. Is that right?
I’ve also read that it looks like a wetter that normal Autumn and Winter here, but assumed that this wasn’t associated with La Niña on the basis that the phenomena breaks down in out autumn. Any brief explanations and or sources I can look at to clarify further? Cheers.
Yeah I saw the indicators in global, seasonal forecast models regarding the double-dip and the Pacific was primed for it, as well as the weather we were continuing to receive in the form of mid-latitude systems.
That was last year.
This year the signal is still strong throughout the Pacific, hence still affecting our weather and climate. Most models are sticking with a return to neutral but there is a bit of a cold pool starting to form in the sub-surface eastern Pacific and it won't take much increase in the trades heading into our winter/spring to kick it back over a third time.
Current forecasts have stronger than normal trades kicking back up over the next week or so, so it might be a case of just drawing out the tail of the double-dip but it looks like a Niña influence is here to stay through autumn and early winter..
Here are the surface heat anomalies from about a year ago through to now and you can see the surface has started cooling already after warming through the start of the year. Read it top to bottom timeline wise.
Such a fascinating thought process when the effect becomes the cause in a never ending spiral of events. Especially when you inject a little gut feel into the wheel.
Foreboding chart Craig. Can you stretch it back in time?
Unfortunately I can't find any archive charts or ones that go back beyond those dates.
Thanks for searching.
Where i live it rains about once every two months. all our water supply comes from underground and i cant understand how so much water is used and the water supply underground can supply everyones water use.(especially with reticulation supplying everyone's lawns and gardens.)
This summer was the hottest ive ever experienced (53 'C on christmas day and average of 41' C most days. great as i have a pool but for most people here way too hot to live comfortably.
Air conditioning is a must where i live.
Living just north of Coffs we’ve had 3 straight summers now with double the avg rainfall. This year has been very strange though. A mate in cairns has had a dry summer (below avg rain). Not a huge amount of cyclone activity for the eastern Australian tropics and coral
Sea this summer.
Yeah if there is a 3rd dip on the cards im dead set moving, no joke
Sorry about the endless rain.
From a purely selfish point, I'll very happily take another La Nina. It's been 5 months of perfect summer weather and non stop surf where we are.
Just call that 3rd one Craigos and I'm on the road, driving into the rising sun...
Hey Craig,
Quick question, slightly off-topic. Just wondering if you are mostly self-taught in relation to meteorology/oceanography or studied at a higher level?
Only asking as your science communication is exemplary.
Cheers for the informative and well-written articles.
Thanks LL.
I'm a University taught Oceanographer and Meteorologist, acquiring first class honours in Oceanography.
I started my path down an Engineering pathway (Computer Systems Engineering with Finance) but after completing 3/5 years, it wasn't for me so shifted Uni's to an Ocean and Climate Sciences degree at Flinders in South Australia.
If you'd stuck with your original pathway you'd be retired by now :-P
Lucky for us.
Haha, yep lifestyle choices!
I thought as much... Haha ahh surfing always influencing life decisions.
Yeah your writing is on point, especially where science communication is such a needed and under-appreciated tool to have in today's society.
"winds have actually been more east across Victoria and South Australia. It's just the lack of quality swell that's been the main issue."
If you live /surf on Vics surf coast east winds are still just plain crap.
Of course, but better than south-east which writes off everywhere. The Surf Coast is never decent through summer.
True - never great in Summer ...but I can't remember a summer worse than this on the surf coast !
If you call "decent" what it's usually like in winter then, yes, you're right. But there are still regularly good days with the hairdryer offshore N/NW blowing and a bit of swell, and we have only had a single one of them this Nov-March on NYE, and even then it wasn't a good one. Pretty much any swell has been corrupted with south/easterly wonk, and it's hardly been offshore.
True.
I'm pretty keen on a three peat
Cmon Huey, most cantankerous of lords, most recusant of deities, the definition of refractory, throughout this summer in Victoria indeed you've proven beyond any who would question or doubt that you are the supreme ruler of all who seek to master the wave energy flux and no Tulla Tub can ever replace thou who delivers the big juicy stuff
Now flip the faarken switch already
Lingering La Nina...
https://www.news.com.au/technology/environment/bureau-of-meteorology-say...
Yep, as mentioned above in a bit more detail in my response to Batfink. Will have an update today.
Can the update please be that it's moved away from southern coasts and surf coast is about to pump for months. Thanks
I might have asked this before, Craig, but with regard to the triple threat La Nina and it being in the mid-70s then late-90s.....
20 years or so ago, an old colleague of mine started a PhD on coastal erosion and used the Byron area as a case study. I'm not sure if he finished it but, essentially, his work was showing that the big erosion events seemed to operate on decadal cycles of 20-30 years. These triple-dip La Ninas would seem to support that to a degree. Do you know much about that as an actual or theoretical phenomenon? Apologies if I've asked that before.
Yes they would especially with the mean swell direction swinging from the south to more east, and also with more consistent storms. This would lead to erosion in those southern corners which are usually sheltered away from the main swell energy.
Thanks Craig. But I'm still wondering whether the decadal cycles are legit or a figment of his imagination....he was pretty out there at times.,,,,brilliant, but loose.
Hey @theswellnet team, hope you’re all well and tuck into plenty over the next east coast swell run!
Had a quick question in regards the extended double dip La Niña conditions and Fiji. Planning a possible trip to remote Fiji, the area receives the same swells at Namotu just shave 30-40% off the size however the season is traditionally October to April when the winds blow nor nor west offshore
Given the extended double dip La Niña conditions are you able to offer any advice on the likely hood of the wind conditions remaining generally favourable? In effect winds from the S is when the party gets spoiled.
Current on the ground reports from a mate near Namotu bode pretty well with both SP & WP having been offshore & on the pump! The area we were looking at require the same nor / nor west winds.
Thanking you in advanced.
Cheers, Leeroy
Ps. I wont hold you to anything :)
Bump!
Quick question but the answer unfortunately isn't an easy one to decipher. Would take a lot of research and investigation unfortunately.
It all depends on the position of the South Pacific Convergence Zone which is a tricky beast.
Thanks Craigo I figured as much. It’s a little bit of a mission to get to the area but might wing it for a few days and possibly mix up the rest of the trip with a few days around Namotu to be safe.
On anecdotal advice from a mate / surf guide near Namotu and a gut feeling I have a sneaking suspicion there’s a fair chance for favourable winds but it’s also another 5-6 weeks away so who knows. I’m certainly no weather / forecasting wizard particularly for that region.
I’ll keep my fingers crossed that winds remain prevalent out of the N / NW quadrant well into the season against the grain.
If you had to make a very brief judgment call what would be your gut feeling be? eg 25% 50% 75% chance?
Your hunch would add some body to the addition of my fingers been crossed