Australia weather: BOM declares La Nina likely ‘near its end’


The Pacific Ocean climate driver that has caused havoc for three years, including delivering multiple deadly floods, is officially “near its end,” the Bureau of Meteorology has declared.

The disappearance of La Nina will likely lead to far less moisture particularly across Australia’s east.

And a swing back towards El Nino will almost certainly bring warmer conditions. And with all the lush greenery after years of rainfall has brought, there’s a potential for more bushfires too.

Although weather experts have said a return to drought conditions might not be on the cards just yet.

La Nina is one extreme of the climate driver known as the El Nino – Southern Oscillation (ENSO).

During a La Nina phase, cool waters from the depths of the Pacific Ocean are hauled up to the surface around the equator. Winds then push warmer seas towards Australia which aid in the creation of more clouds, moisture and windier conditions for the continent.

Conversely, an El Nino can see Australia become far drier.

La Nina did tail off in January 2022, but then came back again later in the year.

A climate driver update released by the BOM on Tuesday said La Nina was fading once more.

“La Nina has weakened in the tropical Pacific Ocean and is likely near its end,” the agency stated.

“Ocean indicators of La Nina have returned to neutral levels, while atmospheric indicators that remain at La Nina levels have started to weaken.”

The ENSO is measured chiefly from an area of the equatorial Pacific known in the meteorological community as “Nino 3.4” which is south of Hawaii and close to Kiribati.

All but one of the main global climate models for surface temperatures in this zone are at a neutral level meaning neither La Nina or El Nino has the upper hand.

The US’ National Oceanic and Atmospheric Administration (NOAA) has released its official predictions for how ENSO will go up until October (see above) with the increasing likelihood an El Nino will take over as we get deeper into the year.

The BOM has said it’s likely the ENSO will remain in neutral throughout autumn. But beyond that modelling can less exact.

A neutral ENSO also allows other climate drivers to get in on the action and affect Australia’s weather.

One of those is the Southern Annular Mode (SAM), a belt of winds that pushes up from Antarctica.

It’s currently in a positive mode, which decreases the chances of cold fronts pushing inland. But like ENSO it’s heading towards neutral.

As is the Indian Ocean Diploe (IOD), which is similar to ENSO but off Australia’s west coast.

Outlook for Australia’s weather

So what does this all mean for Australia’s weather over the coming months?

“From March to May, there are indications rainfall will generally be below average in the south and east, but above average for parts of the north,” the BOM stated in a long range forecast from February.

“(The outlook is for) above average maximum temperatures for the southern two thirds of the nation.”

Some parts of the tropics and the Top End can still expect to see higher than average rainfall during autumn.

Likliehood of droughts coming back

Writing on academic website The Conversation Abraham Gibson from Southern Cross University and Danielle Verdon-Kidd from the University of Newcastle said it was “too early to tell,” if the move away from La Nina would eventually lead to significantly warmer El Nino conditions.

“Nor can we say Australia is about to swing back into drought, as many people fear, after three years of heavy rain associated with consecutive La Ninas.”

That’s because of the multitude of other climate drivers, including the SAM and IOD, which come into play.

“All three climate modes (El Nino, the IOD and the SAM) acted in concert to sustain and prolong the Millennium Drought over a vast area,” said Gibson and Verdon Kidd.

“A return to El Nino could trigger a drought for some regions of Australia.

“However, our catchments are displaying wet to slightly drier than average conditions and our dams are generally full.

“We would need significant drying for a severe drought such as 2017-2019 or 1982-1983 to take hold.”

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