US weather agency lowers chances of La Nina’s emergence

The Climate Prediction Center (CPC), an arm of the US National Oceanic and Atmospheric Administration (NOAA) has lowered the chance of La Nina emerging during September-November 2024.

“La Niña is favoured to emerge in September-November (60% chance) and is expected to persist through January-March 2025,” it said in its lates update.

Last month, CPC had predicted a 71 per cent chance of La Nina emerging in September-November 2024. However, it forecast the weather event, which brings heavy rains and floods to Asia - particularly India- and leads to drought in the Americas, to persist through January-March 2025.

Australian forecast

Last week, Australia’s Bureau of Meteorology a week La Nina could emerge later this year and it could turn neutral by February 2024. It said ENSO (El Nino-Southern Oscillation) and Indian Ocean Dipole are currently neutral. 

CPC said, “The latest North American Multi-Model Ensemble (NMME) forecasts were warmer this month, but still predict a weak La Niña.”  

As a result of the warmer predictions and the recent weakening of equatorial trade winds, CPC still favours a weak event but has lowered the chances of La Niña. 

“A weaker La Niña implies that it would be less likely to result in conventional winter impacts, though predictable signals could still influence the forecast guidance,” said the US agency.

IRI plume indication

The IRI (Jnternational Research Institute for Climate and Society) plume predicts a weak and short duration La Niña, as indicated by the Niño-3.4 index values less than -0.5C. 

CPC said during September 2024, ENSO-neutral continued with near-average sea surface temperatures (SSTs) observed across most of the central and eastern equatorial Pacific Ocean. 

The latest weekly Niño indices ranged from +0.2C (Niño-4) to -0.4C. Below-average subsurface temperatures persisted across the east-central and eastern equatorial Pacific Ocean. Collectively, the coupled ocean-atmosphere system reflected ENSO-neutral, said the US weather agency.