With various global weather models forecasting that La Nina will set in around June this year, an Australian weather firm says La Nina conditions, which will likely emerge in the second half of 2024, have developed more often than El Nino since 1997-98. But things could reverse. 

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“Up until the 1997-1998 El Niño there was more often El Nino conditions and less often La Nina conditions, but from then onwards there has been more often La Nina conditions and less often El Nino conditions,” said the Sydney-based Weatherzone.

This pattern, connected to long-term climate oscillation, could reverse back to more El Ninos in the future, the firm, earlier known as The Weather Company, said. 

Change by spring

After three years of La Nina, which leads to the cooling of the Pacific Ocean and more rains for Asia and drought for the southern US, the global weather faced El Nino, which results in the Pacific Ocean warming up and drought and dry phase in Asia, starting June 2023.

“...but there is a significant chance that the Pacific Ocean returns to a La Nina state by spring this year... The 2010-2011 La Nina event demonstrates that such a short turnaround can happen, and computer models have been consistently predicting La Nina as more likely than either El Nino or neutral conditions,” said the Weatherzone.

La Nina has currently become the more common phase of the El Nino Southern Oscillation (ENSO). “We can see that by looking at the multivariate ENSO index (MEI) for the past several decades from 1979 to 2023. The MEI considers atmospheric variables (cloud, pressure and wind patterns), in addition to the Pacific Ocean’s surface temperature pattern, giving a more holistic index than other indices,” it said.

Atmosphere not linking up

Though the oceanic component of El Nino has been quite strong, according to the composite MEI value, it has been rather weak overall due to the atmosphere not linking up strongly with the ocean. 

“In fact, the Southern Oscillation Index (SOI) that measures the pressure pattern associated with ENSO has been above -7 (SOI value) since December 2023, so technically the atmosphere is not currently coupled with the ocean,” said the weather firm.

The Australian weather firm’s observation comes on the heels of the Climate Prediction Center (CPC), a unit of US National Oceanic and Atmospheric Administration, that there is a 55 per cent chance of La Nina setting in during June-August. “(La Nina) chances increase through the September-November season,” CPC said. 

The US climate agency said since late December 2023, positive SST anomalies have weakened across most of the Pacific. 

2010-11 quick turnaround

According to the Columbia Climate School International Research Institute for Climate and Society, chances are higher for La Nina conditions than either El Nino or neutral conditions for during the August-September-October period.

Weatherzone said in 2009-10 El Nino set in after weak-to-moderate La Nina conditions during 2007-09. The El Nino broke down quickly and a strong La Nina emerged in 2010-11, which witnessed Australia getting its first and second wettest years. 

“So, it would not be surprising if we see La Niña conditions return this year,” said James Rout in the Weatherzone.

Also read: January turns out to be warmest on record; La Nina will likely to set in during Q3 

Referring to sea  temperatures, the weather firm said between September and December 2023 there has been cooling of the eastern Pacific Ocean: It said US and Canadian models predict the trend to continue and La Nina to develop by (southern hemisphere) spring (September).