La Niña: Flicking the switch

Craig Brokensha
Swellnet Analysis

The switch is about to flick....finally!

Back in September, we mentioned the developing La Niña and how that would play out for weather and swell, and for that first half of spring the pattern held true.

Last month, however, the link was broken between the La Niña signal in the Pacific Ocean and Australia's weather and climate.

The main reason was that the subtropical high sat too far north across Australia, allowing cold fronts to steer up and across Western Australia, though deflecting south-east across the south-east of the country, drawing in heat from the north. November ended up being the hottest on record for the country, while rainfall was below average, especially for those coastal locations that are usually soaked during a La Niña spring.

North and east swells were also sporadic on the East Coast with weeks of south swell passing at a time. The South Australian coast and exposed Victorian breaks benefited though with swells from the west along with favourable winds

The MJO, or Madden-Julian Oscillation (a wave of tropical activity that propogates west to east around the globe), has also been subdued and stuck west of us, towards Africa.

As the MJO moves in across northern Australia we'll see a resumption of the classic La Niña pattern. The Southern Ocean storm track will shift towards Antarctica (known as a positive Southern Annular Mode), allowing the subtropical high to also shift south, bringing moist, onshore winds to the East Coast.

The combination of warm, moist easterly winds and tropical activity will bring wet weather to large parts of the country, but more importantly where it's needed across the north and north-east.

Below is the total rainfall forecast for the coming ten days, and while it shouldn't be treated as gospel, it's a good indicator for changing weather patterns.

ECMWF total precipitaion forecast +234hrs (10 days) Source: Weatherzone

As for surf, the subtropical high setting up camp across the Tasman Sea and then New Zealand will direct persistent easterly trade-winds towards the East Coast. Combine this with the odd embedded low squeezing the ridge from the north, and we're looking at an extended run of moderate to large easterly trade-swell.

Keep an eye on the regional Forecaster Notes for the finer details on timings, local winds, and sizes.

Surface wind forecast showung the subtropical high sitting across the Tasman Sea, squeezed by tropical activity to the north

Comments

Lottolonglong's picture
Lottolonglong's picture
Lottolonglong commented Monday, 7 Dec 2020 at 2:29pm

Lake Eyre will need a surf lakes plunger

Redmond Clement's picture
Redmond Clement's picture
Redmond Clement commented Monday, 7 Dec 2020 at 3:03pm

For some reason my recently choreographed rain dance doesn't seem to be working for the North West. The grass is definitely greener every where else. Could get some northerly swell by the looks.

velocityjohnno's picture
velocityjohnno's picture
velocityjohnno commented Monday, 7 Dec 2020 at 3:50pm

Huey has been rewarding Vic for everything they went through, and gave us a little Winter in Novermber/December. Feels like winter today!

freeride76's picture
freeride76's picture
freeride76 commented Monday, 7 Dec 2020 at 3:51pm

those cold fronts and lows have been fun here for surf but it's now time for some proper weather.

Spuddups's picture
Spuddups's picture
Spuddups commented Monday, 7 Dec 2020 at 4:42pm

Intriguing.

_Bodhi_'s picture
_Bodhi_'s picture
_Bodhi_ commented Monday, 7 Dec 2020 at 4:57pm

Yes, finally. Thank you Santa!

Halfscousehalfcockneyfullaussie's picture
Halfscousehalfcockneyfullaussie's picture
Halfscousehalfc... commented Monday, 7 Dec 2020 at 7:02pm

Here comes the big wet? looks prolonged

gekatmargs's picture
gekatmargs's picture
gekatmargs commented Monday, 7 Dec 2020 at 11:02pm

South west corner has had double it average rainfall in November and plenty of cold onshore winds. Very unseasonal

Glenatmargs

thedrip's picture
thedrip's picture
thedrip commented Monday, 7 Dec 2020 at 11:29pm

So what exactly does this mean for SW Western Australia then? We surf over here too.

Craig's picture
Craig's picture
Craig commented Tuesday, 8 Dec 2020 at 8:21am

The South West to Perth region have been under the infleunce of persistent mid-latitude frontal activity which bought that cooler, wetter weather, and also suppressed the strong sea breezes that usually kick in by now.

You can see this in the Mean Sea Level Pressure anomaly for November - lower than normal pressure sitting south of the state, steering cold fronts up across the South West..

The effect of La Niña/El Niño to weather/swell for the west of the country isn't as strong compared to the east (due to the distance from the Pacific Ocean), with the Indian Ocean Dipole likely playing a larger part.

In saying this, the coming month looks fairly subdued with the positive Southern Annular Mode keeping swell producing storms restricted to the polar shelf and with limited strength.

With a large blocking setup stretching west across the southern Indian Ocean, squeezed by inland heat troughs, it looks like we'll see those strong southerly windy days kicking in as well.

thedrip's picture
thedrip's picture
thedrip commented Saturday, 12 Dec 2020 at 2:18pm

Cheers, Craig.

Daveharro's picture
Daveharro's picture
Daveharro commented Tuesday, 8 Dec 2020 at 12:45am

Yep request Xmas period forecast for SW WA as we survive famine and feast here at this time especially if you are in Perth. Thanks

Harrydog

freeride76's picture
freeride76's picture
freeride76 commented Tuesday, 8 Dec 2020 at 11:27am

can you Viccos crow-eaters and sand-gropers keep your heads out of the ENSO threads

this is a pacific thing.

El Niño–Southern Oscillation is an irregularly periodic variation in winds and sea surface temperatures over the tropical eastern Pacific Ocean, affecting the climate of much of the tropics and subtropics.

WardGushee's picture
WardGushee's picture
WardGushee commented Tuesday, 8 Dec 2020 at 4:54pm

Thanks Craig

It has been really dry up on the sunny coast. A chunk of rain will really help.

Are you still catching waves around North Steyne?

All the best,

Ward

Craig's picture
Craig's picture
Craig commented Wednesday, 9 Dec 2020 at 5:53am

Hey Ward! Good to hear from you. Yep, still out there daily, got pretty hectic crowd wise when the lockdowns first kicked in but has settled back down a bit now.

mowgli's picture
mowgli's picture
mowgli commented Thursday, 10 Dec 2020 at 1:26pm

bugger! I haven't finished me landscaping yet!!!!

nah....yeah...but, nah

southey's picture
southey's picture
southey commented Sunday, 13 Dec 2020 at 12:44am

Next weekend is looking interesting .
Gotta love all that Cool water out in the Central Pacific, even down into subtropical lattitudes .
How many times would have this system out off the Solomons have slid off SE in the last decade .
Bring back the retrograde ..... !

" SA's Reserve Capacity "

freeride76's picture
freeride76's picture
freeride76 commented Sunday, 13 Dec 2020 at 6:48am

it will slide off too the SE eventually Southey.
Unfortunately, just when it gets in the swell window.

swing and a miss.

southey's picture
southey's picture
southey commented Sunday, 13 Dec 2020 at 10:07pm

I beg to differ . The cradle winds will sharpen Friday . Core will move into swell window Sat. and then Sunday we have the start of SSW movement .
Personally i think its now definitely not wizzing off to the SE .
How quick it moves will effect your region , but for the rest of NSW its a matter of how long it holds before transition into an Tasman cold core ECL .
Regardless it will produce waves .

" SA's Reserve Capacity "

freeride76's picture
freeride76's picture
freeride76 commented Monday, 14 Dec 2020 at 12:41pm

yep, you're right .

looks to come down the pipe with a slight SSW wobble to it.

dawnperiscope's picture
dawnperiscope's picture
dawnperiscope commented Tuesday, 15 Dec 2020 at 12:40pm

'twas the night before christmas...
and every right hand point on the east coast was lit up!

Ride on

freeride76's picture
freeride76's picture
freeride76 commented Thursday, 14 Jan 2021 at 11:50am

Looking at the ASCAT and synoptics- storm track and jet stream- of the North Pac and the facts of back to back huge swells at Mavs, many, many Pipe days and more to come.......

it looks like the North Pac is in a full blown El Nino.

Craig, do you have any theories to account for it?

stunet's picture
stunet's picture
stunet commented Thursday, 14 Jan 2021 at 12:05pm

Odd, eh? Each time I open the WAMs to see if there's any action up north I see long period swells, all coloured purple, pink, and even black, rounding the Solomon's and heading into the deep South Pacific.

Hawaiian swells. Lots of them. Yet nothing of note in the Coral Sea aimed our way.

Anyway, Craig's working on a La Nina update as we speak.

Stay tooned...

Craig's picture
Craig's picture
Craig commented Thursday, 14 Jan 2021 at 12:14pm

Yeah it's fascinating and not a Niña setup at all. The Northern Hemi activity looks to be linked to a Sudden Stratospheric Warming (SSW) event that took place at the start of the month..

You can see the disruption in the below diagram, this is the AO (same as the AAO/SAM in the Souther Hemi), and you can see the disruption filtering down from the upper atmosphere (light blue) down to the surface over the coming couple of weeks..

That doesn't explain the bombing lows that generated the Mavs swells last weekend though. And these SSW events usually impact the Europe and Asia regions. Trying to find out more.

freeride76's picture
freeride76's picture
freeride76 commented Thursday, 14 Jan 2021 at 11:52am

meanwhile we have a very un-La Nina like major series of S swells on the cards.

Craig's picture
Craig's picture
Craig commented Thursday, 14 Jan 2021 at 12:16pm

The strengthening Long Wave Trough node looks linked to a dip in the SAM to negative territory, though bouncing back quick ahead of the MJO again.

freeride76's picture
freeride76's picture
freeride76 commented Thursday, 14 Jan 2021 at 1:20pm

pretty sick looking south swell progressions though.

that might move some sand into more favourable positions here if we get some longshore drift with it.

Craig's picture
Craig's picture
Craig commented Thursday, 14 Jan 2021 at 1:24pm

Oath.

Blowin's picture
Blowin's picture
Blowin commented Thursday, 14 Jan 2021 at 1:44pm

Feels like La Niña has absconded.

This is our third ( maybe fourth ) full sun day in about a month. I miss the rain already !

velocityjohnno's picture
velocityjohnno's picture
velocityjohnno commented Thursday, 14 Jan 2021 at 1:56pm

Winter continues down here. We've had maybe 4 hot days all summer. Neighbours have had fireplace going on cooler days, grass is still green (very green!), people mention 'we haven't had a summer' in casual chat. 18 degree water temp, grey skies though thankfully a bit of swell and W in the wind now. WOL posted an article saying "Victoria will see boardies" in the CC thread; based on the last 2 summers, yeah nah.

Craig's picture
Craig's picture
Craig commented Thursday, 14 Jan 2021 at 2:02pm

Shows how much the water temps in the Bay and Strait rely on solar heating to warm up in summer eh, instead of currents.