The Climate Prediction Centre (CPC) of the US National Oceanic and Atmospheric Administration (NOAA) has noted the presence of La Nina conditions currently. However, the Ocean Nino Index (ONI) value has not yet reached the threshold required for officially declaring La Nina.
CPC defines El Niño or La Niña conditions as occurring when the monthly Niño3.4 OISST departures meet or exceed +/- 0.5ºC, accompanied by consistent atmospheric features, and forecasted to persist for 3 consecutive months. The most recent ONI value (October-December 2024) is -0.4ºC, and the value for November-January is still pending to confirm the emergence of La Nina.
The ONI is a rolling 3-month average temperature anomaly in the surface waters of the east-central tropical Pacific Ocean. CPC indicated that negative subsurface temperature anomalies strengthened in December 2024 but then weakened in January 2025, suggesting a lack of sustained atmospheric and oceanic responses.
According to the Australia Bureau of Meteorology (BoM), the El Niño–Southern Oscillation (ENSO) has remained neutral for the past 6 months, despite changing sea surface temperature patterns consistent with a potential La Niña event. While conditions have been more La Niña-like in the tropical Pacific, a sustained atmospheric and oceanic response is yet to be observed.
The international models surveyed by BoM predict a neutral ENSO outlook from March to June. CPC mentioned that upper ocean heat anomalies and oceanic thermocline slope index reflect La Nina conditions. There is a 59% chance of La Nina conditions persisting through February-April 2025, with a 60% chance of transitioning to ENSO-neutral during March-May 2025.
Looking ahead to the Northern Hemisphere spring and summer, CPC stated that ENSO-neutral is favored by the dynamical model average, while La Niña is expected to persist based on the statistical model average. BoM highlighted the late development of a potential La Niña event historically, noting that La Niña has a weaker association with Australian temperature and rainfall patterns in summer compared to winter and spring. The Indian Ocean Dipole (IOD) is currently neutral, with global sea surface temperatures above average.
