La Niña Alert

Craig Brokensha
Swellnet Analysis

We're not there yet, but the likelihood of a coming La Niña has greatly increased.

This week, the Bureau of Meteorology upgraded its ENSO outlook to La Niña Alert, which puts the chance of La Niña forming in the coming months at 70% - that's three times the normal likelihood.

Despite not having passed the threshhold yet, the developing La Niña has already been influencing the surf and weather. Historically, the emerging stage of a La Niña event sees increased rainfall across Eastern Australia, and this has been the case. For example, a year ago Warragamba Dam, Sydney's main water supply, was under 50% capacity but now the dam is overflowing.

An emerging La Niña will also increase the prominence of cut-off lows and the clustering of storms, which we've been analysing on Swellnet.

Following this week's announcement, Dr Andrew Watkins from the Bureau said:

"La Niña typically results in above-average winter-spring rainfall for Australia, particularly across eastern, central, and northern regions.  

"It typically also brings cooler and cloudier days, more tropical cyclones, and an earlier onset of the first rains of the wet season across the north.

"The cooling of surface temperatures in the tropical Pacific Ocean and an increase in the strength of the Pacific Trade Winds indicates the chance of La Niña has risen. When these two changes occur at the same time, at this time of year, we see a greatly increased chance of a La Niña forming and persisting through spring. 

"Climate models suggest that further ocean cooling and intensification of Trade Winds may occur over the coming months, which has triggered the Bureau to shift from a La Niña Watch, issued on 26 June, to a La Niña Alert."

Emerging La Niña (source: NOAA)

Chance of exceeding median rainfall through the period September to November (2020) (source: BOM)

Increased rainfall is one thing, but what does an emerging La Niña mean for surf?

La Niña's impacts will be felt mostly across the Eastern Seaboard with more tropical cyclones forecast for the coming season, but as is always the case with small-scale storms, unless there is a supporting ridge of high pressure the benefits are limited.

The long-range Mean Sea Level Pressure forecasting by the European Centre for Medium-Range Weather Forecasts (ECMWF) has such scenario with higher than normal pressure sitting just south of New Zealand and stretching below Tasmania.

With this setup, we'll continue to see swells coming more from the east rather than south into summer, and that bodes well for a reduction of the chances of those pesky northerly winds that have plagued Northern NSW and south-east Queensland the past couple of summers. This is due to the sub-tropical high sitting further south and lower than normal pressure forecast through the Coral Sea.

For the southern states, Victoria and Tasmania are expected to see a little less swell than average owing to higher than normal pressure, while Western Australian is a tricky one to forecast though likely to remain active with mid-latitude frontal systems. Swells across South Australia are likely to sneak in under Western Australia and arrive from the west.

This is a very broad outlook, however, and the regional Forecaster Notes will provide much greater detail and accuracy over the coming months.

Comments

freeride76's picture
freeride76's picture
freeride76 commented Thursday, 20 Aug 2020 at 1:17pm

good summary Craig. cheers.

zenagain's picture
zenagain's picture
zenagain commented Thursday, 20 Aug 2020 at 1:22pm

Please excuse my ignorance, but is this a worldwide phenomenon? For example, we've had here in Japan an abnormally wet wet season (30/31 days of rain in July) and now we're baking here. No waves, been basically flat for four months.

What i'm asking in a roundabout way was last season the snow season was abysmal (by our standards), do you think the northern-hemi winter will deliver this year? I'm thinking of taking advantage of very few tourists going to Hokkaido and Nagano- my version of empty Indo.

1173

Craig's picture
Craig's picture
Craig commented Thursday, 20 Aug 2020 at 3:32pm

Not world-wide but close to. Its effects are felt wide and far from Indonesia, Japan, the US and event the Atlantic. So probably 3/4 of the world and then the tele-connections from there likely fill the gaps.

Last year was terrible linked to the significant + IOD event blocking the monsoon from drifting south, hence keeping warm and southerly storms aimed at Japan through winter. Also the Siberian High failed to really establish with all that record heat.

I'll have to look at what La Nina means for Japan though.

zenagain's picture
zenagain's picture
zenagain commented Thursday, 20 Aug 2020 at 3:46pm

Thanks Legend.

Just quietly, I reckon Niseko/Rusutsu are gonna be worth a short plane ride from here this winter. Can't see the annual influx happening.

1173

mowgli's picture
mowgli's picture
mowgli commented Thursday, 20 Aug 2020 at 11:29pm

I don't know how good these teleconnections he speaks of are (no doubt better than Optus), but you can probably feel the envy emanating from me right now.

“Life is a long lesson in humility.”

wax-on-danielson's picture
wax-on-danielson's picture
wax-on-danielson commented Thursday, 20 Aug 2020 at 8:36pm

I think it mostly effects the Pacific and while East Australia is wetter, the US is drier. Not sure if is a Nth / Sth thing or East / West. Pretty sure it is to do with global ocean currents.
Correct if wrong.

rob tas's picture
rob tas's picture
rob tas commented Thursday, 20 Aug 2020 at 1:52pm

Hey Craig, while tassie might see less southerly swell, we've seen a lot more east coast activity in the past 2months, than we have for years; which i assume would continue with la nina?

Craig's picture
Craig's picture
Craig commented Thursday, 20 Aug 2020 at 3:28pm

Yep, it's all linked.

Plasticspastic's picture
Plasticspastic's picture
Plasticspastic commented Thursday, 20 Aug 2020 at 1:53pm

more swell from the East than the South? fantastic.. also will that include more ESE and SE winds?

Craig's picture
Craig's picture
Craig commented Thursday, 20 Aug 2020 at 3:03pm

Hopefully.

Bungan33's picture
Bungan33's picture
Bungan33 commented Thursday, 20 Aug 2020 at 2:02pm

Adding insult to injury for the horrendous run were having on the surf coast....ffaaarrrkkkk....maybe I should shift back east?

Howie66's picture
Howie66's picture
Howie66 commented Friday, 21 Aug 2020 at 10:07am

I know it’s been super shit hey and at a time when crowds are low.. spewin

Trentslatterphoto's picture
Trentslatterphoto's picture
Trentslatterphoto commented Thursday, 20 Aug 2020 at 2:30pm

west been fucked super wsw swell directions sus tides

Spuddups's picture
Spuddups's picture
Spuddups commented Thursday, 20 Aug 2020 at 4:20pm

Hopefully the rain will mean less bush fires this summer.

mysto83's picture
mysto83's picture
mysto83 commented Thursday, 20 Aug 2020 at 7:17pm

Thanks Craig. Have always wondered about increased surf prospects during la nina on east coast.

Growing up in the northern hemisphere el nino always used to fire up the surf and el nino seasons coincided with places like mavs with foo swell and Jay Moriarty wipeout year spring to mind as being a particularly epic el nino season.

Living in byron and lennox in mid-late 2000s anecdotally la nina summers were always cooler and wetter with regular cyclone action often starting in dec or early jan. There would be days when lennox would be too stormy and windy but places like the pass, main beach byron and Kirra would turn on. I would always think of la nina years as being good years to surf.

Good to know that there is evidence to support this.

Unfortunately I live in vicco now and sounds like converse might be the case during la nina.

markbrett's picture
markbrett's picture
markbrett commented Friday, 21 Aug 2020 at 10:33am

good to hear those 'pesky' northerly winds will be less prolific - the last two years have been nuts. Strong NE' winds from late Sept all the way to January...along with frigid water temps thanks to the upwelling.

Craig's picture
Craig's picture
Craig commented Friday, 21 Aug 2020 at 1:59pm

Wax-on-d the effects are much wider spread. Ie this year's Atlantic Hurricane season is expected to be much more active owing to La Niña bringing less vertical wind shear which otherwise would weaken storms. The Atlantic is very warm as well so it's going to be very active. 

Craig's picture
Craig's picture
Craig commented Friday, 21 Aug 2020 at 2:02pm

Here we go..

geek's picture
geek's picture
geek commented Friday, 21 Aug 2020 at 4:22pm

Would that mean highs sitting either over or to the east of Vicco Craig? (Ie not stuck in the bight)

SA Wetdog's picture
SA Wetdog's picture
SA Wetdog commented Friday, 21 Aug 2020 at 9:07pm

Craig, I bought a house in bilambil heights 2009 and left in 2013. Felt like I had to mow the lawns every fricken day. Rained like crazy, Brisbane floods, Kennedy Dr flooded, rain didn't stop for a good few years ( so it felt) surf pumped though. Lots of rainy sessions from pottsville to snapper. My question is without googling, was this all a la niña? And how long can u expect a la niña to stick around? Thanks in advance

freeride76's picture
freeride76's picture
freeride76 commented Saturday, 22 Aug 2020 at 7:48am

briefly yes.

La Nina 2008-9
2010-12.

they were wet years.

tango's picture
tango's picture
tango commented Saturday, 22 Aug 2020 at 1:15pm

If there is a La Niña and the east coast keeps cooking, can you please set up a firewall at the border so we don't have to see it. It's just gone fully onshore again, the wind chill just made it over zero at 1pm and after all the potential of this low, the surf has been pretty frickin average again. It's getting the point of making summer look good - at least you can still put your socks on after a paddle.

groundswell's picture
groundswell's picture
groundswell commented Saturday, 22 Aug 2020 at 3:46pm

What does that mean for indo and the maldives? i forget

Craig's picture
Craig's picture
Craig commented Monday, 14 Sep 2020 at 10:12am

NOAA have officially called it. We're in La Niña..

"La Niña conditions are present and are likely to continue through the Northern Hemisphere winter - Southern Hemisphere summer (~75% chance)."

https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.shtml