Double-dipping into La Niña

Craig Brokensha picture
Craig Brokensha (Craig)
Swellnet Analysis

If you've been reading Swellnet over the past few years, particularly our weather analysis articles, you may appreciate how certain global climate indices influence the seasonal surf in Australia.

The biggest player in this space is the El Niño-Southern Oscillation (ENSO) which develops along the equator throughout the Pacific Ocean. The ENSO signal starts to form during spring and influences our weather and surf into summer and autumn.

El Niño (Spanish for 'little boy' as Peruvian fishermen noticed it occured around Christmas) develops under a slackening and reversal of the easterly trade winds across the Pacific, which results in warm water building up in the central to eastern Pacific Ocean, with a corresponding cool water signal developing further west, closer to Australia.

The opposite is La Niña (the 'little girl') which sees stronger than normal easterly trade winds (blowing from east to west) cause an upwelling of cool water along the equator in the eastern to central Pacific Ocean, while warm water pools towards the west - meaning the north-east coast of Australia and around Indonesia. 

Neutral events are the most common state that the equatorial Pacific Ocean reverts to, with steady easterly trade winds and convection in the western Pacific Ocean.

Under La Niña setups, the cooler than normal water throughout the equatorial Pacific Ocean suppresses convection (storms/rainfall) in that region while to the west (i.e closer to the Australia) we see increased convection and instability due to the warmer than normal water. This brings increased rainfall to the continent, mainly focussed to the east and north.

El Niños see the opposite occur with a suppression of convection and rainfall in the Australian region (on average - we can still see wet El Ninos), with it enhanced further east towards Central and South America.

Now, not all La Niñas are equal and the same goes for El Niños, they come in different flavours and strengths.

As the the Niña/Niño signal develops across the equatorial Pacific Ocean during our spring, historically the cool/warm water anomaly (measuring the difference from normal) has been positioned towards the east. But over the past few decades we've seen the focus of the temperature anomalies developing further west towards the Date Line (180°).

What this does is shift the general circulation pattern further west, and with La Niña's this means the convection and rainfall is also shifted further west, away from the coastal locations along the East Coast, more inland towards the Murray-Darling Basin and the north-west of the continent.

This variation of the traditional La Niña/El Niño is given the name Modoki (Japanese for 'similar but different').

Following last year's La Niña, and after forecasting the probability of a double-dip La Niña (back to back) event this coming summer, we're currently on the cusp of it coming to fruition.

The difference this year is that we're set to see a bit of a Modoki flavour to the developing La Niña, with the cool sea surface temperature anomalies being strongest further west, towards the Date Line, compared to last year where they were focussed more towards 140-120W. You can see this shift in the two charts below, the first from 2020, the second from 2021. You can also notice the sea surface temperaures in both the Coral and Tasman Sea are a bit cooler than last year.

Last November's classic La Niña signal

This year's developing La Niña Modoki signal

This means that the coming summer and autumn should see moisture focussed more towards central and north-west Australia, however what does it mean for surf potential?

During La Niña, the increased convection and lower pressure across the north of the country shifts the sub-tropical high pressure belt further south during summer. This results in an increase in easterly swell energy across the East Coast, while suppressing the westerly storm track to the polar shelf, further south than normally seen during summer. Meanwhile, the southern states usually experience smaller, weaker swells, and unfavourable winds from the south-eastern quadrant, and that's just what happened across most locations through last summer.

So how does Modoki effect this outlook?

Despite the moisture being focussed more inland, surf wise it looks like we'll see a similar season to the last on the East Coast, with plentiful swell from the east along with more favourable winds (i.e not the usual northerly pattern).

Below is the sesonal forecast (provided by the UK Met Office) for the coming summer months (December, January, February). It shows the probability of lower/higher pressure during the coming three month period.

UK Met Office Mean Sea Level Pressure forecast for October/November/December

Victoria looks to fair a little better, with the position of the blocking high being more favourable than last summer, which was to the south-west of Western Australia. Current seasonal forecasts have it positioned more under Tasmania and across New Zealand which hopefully points to a little more swell action. 

Also, with lower pressure through central parts of Australia it'll hopefully tip winds towards a more east to north-easterly bias, with this hopefully also impacting South Australia.

Western Australia looks to be dry and hot with that low pressure anomaly indicating a semi-persistent heat-trough which will bring gusty offshore winds across the surfable regions, while swell wise they should do a little better than last summer with high pressure anomalies forming further west and east of its immediate swell window. This looks to bring energy more from the south-southwest though.

In summary, when looking at the broad scale synoptics it's looking like an active summer ahead . As always, we'll continue to provide updates on the coming summer season in the comments below.

Comments

Mcface's picture
Mcface's picture
Mcface Wednesday, 13 Oct 2021 at 10:41am

Unreal Craig. Welcome news after 100+ days confined to shit city breaks with out of control crowds.

Glad to hear that our southern brethren will also have a fair chance at scoring too, at least compared to what seemed like a tough year just gone.

blindboy's picture
blindboy's picture
blindboy Wednesday, 13 Oct 2021 at 10:41am

Thanks Craig. Love your work, particularly when it predicts a good season ahead!

christopher.jones's picture
christopher.jones's picture
christopher.jones Wednesday, 13 Oct 2021 at 11:04am

Are we just going to trust the science on this??! Shouldn't we get some Facebook opinions?

:P

freeride76's picture
freeride76's picture
freeride76 Wednesday, 13 Oct 2021 at 11:31am

I think the La Nina pattern is already manifesting quite solidly in the SW Pacific.

Middle of October and the North Coast/SEQLD is yet to get a sustained N'ly episode because alternating high pressure is moving in at the more S'ly latitude Craig mentions above.

Eggman's picture
Eggman's picture
Eggman Wednesday, 13 Oct 2021 at 11:45am

all I see are fractals

Craig's picture
Craig's picture
Craig Wednesday, 13 Oct 2021 at 12:42pm

Ha!

Pat Hollingworth's picture
Pat Hollingworth's picture
Pat Hollingworth Wednesday, 13 Oct 2021 at 2:18pm

yes that NOAA image looking very Mandelbrotlian

sdizzle80's picture
sdizzle80's picture
sdizzle80 Wednesday, 13 Oct 2021 at 4:43pm

same, look pretty awesome

batfink's picture
batfink's picture
batfink Thursday, 14 Oct 2021 at 4:42pm

Exactly Eggman. Note the cold water upswellings which also resemble a very disordered swell, and also clouds that often form at the front of a thunderstorm. Have seen these many times.

Craig's picture
Craig's picture
Craig Thursday, 14 Oct 2021 at 5:17pm

Kelvin Helmholtz instability.

batfink's picture
batfink's picture
batfink Thursday, 14 Oct 2021 at 5:37pm

Ha, thanks Craig, of course there’s a name for it, and of course you knew what it was. 10/10 :-)

Good ole Kelvin, wonder what board he rides these days?

Eggman's picture
Eggman's picture
Eggman Thursday, 14 Oct 2021 at 6:20pm

I thought I was being really cool with fractals but Kelvin takes the cake.

Island Bay's picture
Island Bay's picture
Island Bay Wednesday, 13 Oct 2021 at 11:52am

That looks like SE winds where I am. And we'll take that, thank you very much.

Cheers Craig

Yendor's picture
Yendor's picture
Yendor Saturday, 16 Oct 2021 at 9:32am

The blocking high looks pretty suck for us down here though. Curses! Victoria wins we lose.

Craig's picture
Craig's picture
Craig Wednesday, 13 Oct 2021 at 12:50pm

For those interested in ECMWF's seasonal forecast outlook, here are the probabilities regarding Mean Sea Level Pressure for the according months.

November/December/January

December/January/February

January/February/March

February/March/April

andy-mac's picture
andy-mac's picture
andy-mac Wednesday, 13 Oct 2021 at 1:26pm

Excellent!! Thank you :)

Mad Dog's picture
Mad Dog's picture
Mad Dog Wednesday, 13 Oct 2021 at 1:36pm

Absolutely awesome work Craig, you have really enhanced my knowledge of the weather since undertaking this series of articles and I really appreciate the way you've presented everything.

Thanks brother.

shortenism's picture
shortenism's picture
shortenism Wednesday, 13 Oct 2021 at 2:01pm

Great work!

freeride76's picture
freeride76's picture
freeride76 Wednesday, 13 Oct 2021 at 2:02pm

whoa, thats immense for our surf potential.

Johknee's picture
Johknee's picture
Johknee Wednesday, 13 Oct 2021 at 2:08pm

Best articles on Swellnet. Love your work!

Sprout's picture
Sprout's picture
Sprout Wednesday, 13 Oct 2021 at 2:08pm

Great article Craig.
So is that more cyclones but further away?

Craig's picture
Craig's picture
Craig Wednesday, 13 Oct 2021 at 6:40pm

Here's the cyclone outlook by the BOM.. http://www.bom.gov.au/climate/cyclones/australia/

Pat Hollingworth's picture
Pat Hollingworth's picture
Pat Hollingworth Wednesday, 13 Oct 2021 at 2:19pm

yeeeww

crg's picture
crg's picture
crg Wednesday, 13 Oct 2021 at 2:40pm

I can see your future Craig. You’re wearing a brown suede jacket with leather elbow patches and gentling tugging on an antique pipe whilst explaining the vagaries of climate anamolies to the latest round of eager first year oceanography uni students.
“But Professor Brokensha...what about this possibility?”

Craig's picture
Craig's picture
Craig Thursday, 14 Oct 2021 at 11:43am

Ha!

Blowin's picture
Blowin's picture
Blowin Wednesday, 13 Oct 2021 at 3:18pm

Agree with the appreciation heaped on your efforts, Craig. Learning heaps.

Takeaway from this article for my zone is : Potential for ample East trade swell, less Northerly winds and above average rains without the floods which fucked last summer. Good surfing, good fishing, good growing. Good times.

Nice.

memlasurf's picture
memlasurf's picture
memlasurf Wednesday, 13 Oct 2021 at 4:54pm

Craig what about the warm current which comes around Gabo Island and comes to the MP? This seems to vary heaps from year to year. 2 years ago is was cold all summer, last year was average and some years it is board shorts till April. Is it tied up with the Nina's and Nino's?

cgrover's picture
cgrover's picture
cgrover Wednesday, 13 Oct 2021 at 6:29pm

In SA last summer the surf was even more horrible than usual with the winter being pretty sad for most of the time. Will the swell be better this summer than last, ( I know the winds look SE NE as usual as you said)

Craig's picture
Craig's picture
Craig Wednesday, 13 Oct 2021 at 6:41pm

Swell wise it looks a touch more favourable, but I'd keep your expectations low. Be happy for a peaky Parsons day 1-2x a week maybe..

cgrover's picture
cgrover's picture
cgrover Wednesday, 13 Oct 2021 at 8:04pm

Snafu in SA summer, thanks for the reply

bbbird's picture
bbbird's picture
bbbird Wednesday, 13 Oct 2021 at 7:59pm

"Entering Uncharted Waters" Oxfam world social change charity social /climate impact report from Nov 2015....

There is also emerging evidence that climate change affects the El Niño Southern Oscillation (ENSO) cycle and increases the odds of a strong El Niño taking place.

New research says that as the Earth warms, super El Niños may occur approximately twice as often as before – every 10 years instead of every 20 years – and the opposite phase of the ENSO cycle, the so-called La Niña, when the oceanic circulation goes into reverse, may also become correspondingly more frequent and more extreme. Reference#15

The weather impacts of La Niña are more or less the opposite of El Niño, Ref#16 including bringing drier conditions to the American Midwest. La Niña conditions raise sea levels in the Western Pacific, which increases the destruction caused by storm surges there.

Some new research suggests that a ‘new normal’ will come into being that corresponds more to La Niña, but punctuated periodically by more frequent, extremely hot El Niño events.Ref# 17

Oxfam Report & references from 2015 below
https://oxfamilibrary.openrepository.com/bitstream/handle/10546/578822/m...

views from the cockpit's picture
views from the cockpit's picture
views from the ... Wednesday, 13 Oct 2021 at 8:04pm

Great report
Could be horror on the West Coast for VL again sadly.

greyhound's picture
greyhound's picture
greyhound Wednesday, 13 Oct 2021 at 9:07pm

The horror has already started. about 2/3 weeks ago.

southey's picture
southey's picture
southey Wednesday, 13 Oct 2021 at 10:28pm

Just shift your focus further west . Months of ESE with ENE - LAGO's sounds like heaven to me .

goofyfoot's picture
goofyfoot's picture
goofyfoot Thursday, 14 Oct 2021 at 6:29am

Yeah I’ll take that

Thegrowingtrend.com's picture
Thegrowingtrend.com's picture
Thegrowingtrend.com Wednesday, 13 Oct 2021 at 8:06pm

booya

bbbird's picture
bbbird's picture
bbbird Wednesday, 13 Oct 2021 at 8:22pm

La Niña causes an upwelling of ocean nutrients= plankton = abundant sardines in South America; so a fertile time.
Eating fish increases the chances of pregnancy.
So more waves for us on the east coast of Oz & more babies in Peru.

Blowin's picture
Blowin's picture
Blowin Thursday, 14 Oct 2021 at 7:15am

You don’t think the enhanced fertility of fish consumption will be offset by the contraceptive effects of sardine breath?

bbbird's picture
bbbird's picture
bbbird Thursday, 14 Oct 2021 at 8:22pm

Get a good catch, go to the market; hava few drinks & then a Ceviche (a very popular dish in Peru).. recipe: raw fish + lime juice & wait 5 minutes.
https://en.wikipedia.org/wiki/Ceviche

Dillosurf's picture
Dillosurf's picture
Dillosurf Thursday, 14 Oct 2021 at 8:46am

Hey Craig, great article thanks. Which part of the anomaly comes first? The sea temperature or the wind? I would have thought the sea temperature has more effect on the wind than vice versa. If so do ocean currents first drive the sea temperature?

Craig's picture
Craig's picture
Craig Thursday, 14 Oct 2021 at 8:50am

Great question.

It's the wind.

There is a sub-surface cool water signal that travels from west to east but this needs to be upwelled and the stronger bursts of easterly trade winds are the catalyst for this.

Once it starts going though it's a positive feedback loop with the warmer water to the west causing that rising air which then strengthens the easterly trade winds further, upwelling more cooler water etc.

Craig's picture
Craig's picture
Craig Thursday, 14 Oct 2021 at 8:53am

The correlation between the wind driven surface currents (blue line) and the sea surface temperature signal (red line) is shown clearly below.

You can see the blue line dip negative (westerly flowing currents from the easterly trade winds) which then brings the opposite signal in the sea surface temperature a couple of months later (rising in the Western Pacific)..

Both last year's and the coming La Niña can be seen.

Dillosurf's picture
Dillosurf's picture
Dillosurf Thursday, 14 Oct 2021 at 9:06am

Thanks, that all makes sense.

Squidy's picture
Squidy's picture
Squidy Thursday, 14 Oct 2021 at 9:59am

Criag, if surface water is pushed to the left by winds as explained in one of your earlier articles wouldn't warm water from the north of the equator fill in or is surface water pushed to the right north of the equator thus allowing for the upwellings to occur. BTW great articles and well explained.

Craig's picture
Craig's picture
Craig Thursday, 14 Oct 2021 at 11:44am

Aghh, it's to the left in the Southern Hemisphere, but to the right in the Northern Hemisphere, hence why you're seeing those eddies north of the equator spinning clockwise.

The Coriolis force works in opposite directions in either hemisphere.

harrycoopr's picture
harrycoopr's picture
harrycoopr Thursday, 14 Oct 2021 at 10:11am

Sorry, anti-nina here ....Dribs is always crap with those se winds summerlong. Maybe an odd waits or robe foray.
Pro-vaxxing though... it's a coming. Love the science Craig

dawnperiscope's picture
dawnperiscope's picture
dawnperiscope Thursday, 14 Oct 2021 at 10:24am


upload image

I find this graph interesting in a few ways. One of them is that the La Nina years seem to bring out the "good ol' days" call from the elder statesmen on the Gold Coast. Seems to represent it nicely that the 70's actually was a glorious decade.

Jono's picture
Jono's picture
Jono Thursday, 14 Oct 2021 at 10:39am

GFS got your memo Craig and jumped straight on board

Craig's picture
Craig's picture
Craig Thursday, 14 Oct 2021 at 11:49am

Bingo.

batfink's picture
batfink's picture
batfink Thursday, 14 Oct 2021 at 4:49pm

How apt that I’m reading this as a seriously black thunderstorm passes overhead.

We’ve had a batch of these this Spring, normally don’t see them until December or January.

Of course, may or may not be directly related, but, you know. Weather!

Craig's picture
Craig's picture
Craig Thursday, 14 Oct 2021 at 9:17pm

Seems to be slightly linked but also feeding off the negative Indian Ocean Dipole (which is now weakening). Great show this evening!

Switchfoot bob's picture
Switchfoot bob's picture
Switchfoot bob Thursday, 14 Oct 2021 at 8:53pm

So does this mean less winds from south south west and more from east over summer in sw WA? Also how does this effect the inland temp in the desert east of the west coast? Will that see more rain from tropical lows?

Switchfoot bob's picture
Switchfoot bob's picture
Switchfoot bob Saturday, 16 Oct 2021 at 2:17pm

Hi Craig

Did I ask stupid questions?

freeride76's picture
freeride76's picture
freeride76 Friday, 15 Oct 2021 at 7:04am

Not sure if you timed this article with the current set-up Craig, but the Pacific Basin right now has almost got the perfect La Nina set-up.
E'ly Tradewinds from end to end.
troughs of low pressure where they are supposed to be.

And for Aus- the missing link- which is strong high pressure at southerly latitudes which can tele-connect warm, moist air from the West Pacific warm pool to the East Coast.

It's a thing of beauty at the moment.
And its only October!

Last year we didn't get the set-up until first week of December.

Craig's picture
Craig's picture
Craig Friday, 15 Oct 2021 at 7:32am

Yep, looks like it's already kicking into gear which is great to see!

I was waiting for the BOM to pull the trigger and that upgrade to alert was all I needed to push go.

PabloM's picture
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PabloM Friday, 15 Oct 2021 at 7:41am

Excellent work Swellnet