ENSO Conditions and Coral Bleaching

I) CPC Official Probabilistic Forecast
(based on a consensus of NOAA's CPC and Columbia University's IRI forecasters, using observational information and model output, along with human judgment):

December 11, 2025 (updated early-month)

Alert Status: La Niña Advisory
(definitions)

La Niña is favored to continue for the next month or two, with a transition to ENSO-neutral most likely in January-March 2026 (68% chance)

DIAGNOSTIC DISCUSSION:

La Niña persisted in November, as indicated by the continuation of below-average sea surface temperatures (SSTs) across the central and eastern equatorial Pacific Ocean. The latest weekly Niño-3.4 index value was -0.5°C, with the other Niño index values between -0.2°C and -0.4°C. Recent negative subsurface temperature anomalies weakened slightly (averaged from 180°-100°W), but below-average temperatures continued from the surface to 200m depth in the eastern half of the equatorial Pacific.

The tropical atmosphere reflected La Niña, with low-level easterly wind anomalies evident in the central Pacific and upper-level westerly wind anomalies observed across most of the equatorial Pacific Ocean. Enhanced convection persisted over Indonesia and suppressed convection was near the Date Line. The traditional and equatorial Southern Oscillation indices were positive. Collectively, the coupled ocean-atmosphere system remains consistent with La Niña.

Last month, the IRI multi-model predictions indicated La Niña will continue in the December-February (DJF) 2025-26 season, but then ENSO-neutral is favored for January-March (JFM) 2026. Together with the North American Multi-Model Ensemble, the team continues to slightly support a weak La Niña through DJF (54% chance), before transitioning to ENSO-neutral in JFM. Even after equatorial Pacific SSTs transition to ENSO-neutral, La Niña may still have some lingering influence through the early Northern Hemisphere spring 2026 (e.g., CPC's seasonal outlooks).

... Read more at the NOAA's Diagnostic Discussion, CPC ENSO Update, and CPC's Official Probabilistic ENSO Forecast sites, all updated at the same time in the early-month.

** Note: IRI's Monthly Ouick Look updates twice per month and presents the latest update between the (I) early-month CPC official Probabilistic Forecast (shown in this section) and (II) mid-month IRI Model-Based Probabilistic Forecast (shown in the following two sections).

(The update of the CPC ENSO diagnostics discussion and forecast is scheduled for the second Thursday of each month.)

II) IRI Model-Based Probabilistic Forecast
(a purely objective ENSO probability forecast that uses as input the model predictions from IRI's ENSO Predictions Plume):

December 19, 2025 (updated mid-month)

Tthe probability of La Niña at 56% for Dec-Feb 2026. From Jan–Mar 2026 onward, the forecasts begin shifting toward ENSO-neutral,

As of mid-December 2025, the equatorial Pacific is in a La Niña state, with sea surface temperatures in the Niño 3.4 region having crossed the La Niña threshold. The CCSR/IRI ENSO plume forecast places the probability of La Niña at 56% for Dec-Feb 2026. From Jan–Mar 2026 onward, the forecasts begin shifting toward ENSO-neutral, which is forecast to become the dominant category. Neutral probabilities rise to 64% at the start of the year and remain the leading state through the forecast period ending in Aug–Oct 2026. El Niño probabilities stay very low, below 10% through Mar–May 2026, but gradually increase thereafter, reaching 14% in Apr–Jun, 26% in May–Jul, 35% in Jun–Aug, and 38% by Jul–Sep 2026.

... Read more at the IRI Technical ENSO Update, IRI Model-Based Probabilistic ENSO Forecast, IRI ENSO Predictions Plume, and IRI Forecast Probability Distribution Based on the IRI ENSO Prediction Plume sites, all updated at the same time in the mid-month.

** Note: IRI's Monthly Ouick Look updates twice per month and presents the latest update between the (I) early-month CPC official Probabilistic Forecast (shown in this section) and (II) mid-month IRI Model-Based Probabilistic Forecast (shown in the following two sections).

(The update of the IRI ENSO forecast is scheduled for the 19th of each month. If the 19th falls on a weekend or holiday, it is released on the closest business day.)

III) IRI ENSO Predictions Plume
The following graph shows forecasts made by a set of dynamical and statistical models for SST in the Niño-3.4 region, for nine, overlapping, three-month periods.

December 19, 2025 (updated mid-month)

The IRI ENSO prediction plume indicates a moderate likelihood of La Niña conditions during Dec–Feb 2025/26, with a 56% chance. The multimodel mean of statistical and dynamical models suggests La Niña conditions are likely to transition to ENSO-neutral in Jan-Mar 2026 (64%), and ENSO-neutral conditions are expected to become dominant once again. During this period, the chances of El Niño development remain minimal through the first quarter of 2026, but then gradually rise, reaching to a highest probability of 38% in Aug-Oct 2026. However, such long-lead forecasts remain highly uncertain, as they pass through the spring predictability barrier.

... Read more here, where any specific model can be interactively examined, along with other detailed information.

(The update of the IRI ENSO forecast is scheduled for the 19th of each month. If the 19th falls on a weekend or holiday, it is released on the closest business day.)

Historically Speaking & More:

El Niño and La Niña events tend to develop during the period Apr-Jun and they

Tend to reach their maximum strength during October - February
Typically persist for 9-12 months, though occasionally persisting for up to 2 years
Typically recur every 2 to 7 years

The spring predictability barrier: Forecasts made at some times of the year generally have higher skill than forecasts made at other times of the year -- namely, they are better when made between June and December than when they are made between February and May. This is a well-known challenge for forecaster and it can impact statistical models more than dynamical models.

Disclaimer

The content posted on this web page solely represents the opinions of the authors and does not constitute a statement of policy, decision, or position on behalf of NOAA or the US Government.

The appearance of external links on this World Wide Web site does not constitute endorsement by the Department of Commerce/National Oceanic and Atmospheric Administration of external Web sites or the information, products or services contained therein. For other than authorized activities, the Department of Commerce/NOAA does not exercise any editorial control over the information you may find at these locations. These links are provided consistent with the stated purpose of this Department of Commerce/NOAA Web site.