Chances of La Nina, which results in heavy rainfall and floods particularly in India, emerging after June have increased even as El Nino is dissipating, two global weather agencies have said.

“El Nino continues and is near its end….While three out of seven international models are predicting a La Nina by late winter,” said Australia’s Bureau of Meteorology (BoM).

According to the Climate Prediction Center (CPC), an arm of the US National Oceanic and Atmospheric Administration, there is a 62 per cent chance of La Nina emerging during June-August — a 7 percentage point increase from the 55 per cent chance two weeks ago. 

“A transition from El Niño to ENSO-neutral is expected by April-June season 2024, with ENSO-neutral persisting through May-July 2024. Thereafter, La Nina is favoured in June-August, and chances increase through the October-December season,” CPC said in its latest update.

Models’ indication

A majority of models indicate El Nino will persist through March-May 2024 and then transition to ENSO-neutral during April-June 2024. After a brief period of ENSO neutral conditions, most models indicate a transition to La Nina around June-August 2024, the US agency said. 

BoM said climate models indicate that sea surface temperatures in the central tropical Pacific are expected to return to ENSO-neutral later in autumn 2024. El Nino, which emerged in June 2023, has in particular affected India with deficient rainfall in at least one-fourth of the country. The south-west and north-east monsoons, besides winter (January-February), have witnessed deficient rainfall. 

Negative subsurface temperature anomalies expanded across the equatorial Pacific, CPC said. Such a development is associated with the development of La Nina, weather experts say.

“Subsurface temperature anomalies have weakened since late November 2023. Since late January 2024, negative temperature anomalies have gradually strengthened, it said.

Australia’s BoM said atmospheric indicators are consistent with a decaying El Nino. “The 90-day Southern Oscillation Index (SOI) is currently −3.7, indicative of ENSO-neutral conditions,” it said.

Neutral ENSO

International climate models suggest the central tropical Pacific Ocean will continue to cool in the coming months, with four out of seven climate models indicating the central Pacific is likely to return to neutral El Nino–Southern Oscillation (ENSO) levels by the end of April (neither El Nino nor La Nina), and all models indicating neutral in May,” the Australian weather agency said.

CPC said during the last 4 weeks, above-average sea surface temperatures (SSTs) weakened across most of the equatorial Pacific Ocean. “In the last couple of weeks, below-average SSTs emerged in a small region of the eastern Pacific Ocean,” it said.

During the last four weeks, negative SST anomaly changes were observed over most of the equatorial Pacific, but were strongest in the eastern Pacific, it said, projecting that El Nino is all set to dissipate.

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