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):

November 13, 2025 (updated early-month)

Alert Status: La Niña Advisory
(definitions)

La Niña is favored to continue into the Northern Hemisphere winter, with a transition to ENSO-neutral most likely in January-March 2026 (61% chance)

DIAGNOSTIC DISCUSSION:

La Niña continued over the past month, as indicated by the strengthening of below-average sea surface temperatures (SSTs) across the central and eastern equatorial Pacific Ocean. The latest weekly Niño indices were between -0.5°C and -0.7°C, with the exception of the easternmost Niño-1+2 index at -0.2°C. Negative subsurface temperature anomalies persisted (averaged from 180°-100°W), with below-average temperatures prevailing from the surface to 200m depth in the eastern half of the equatorial Pacific.

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

Last month, the IRI multi-model predictions favored La Niña to continue through December-February (DJF) 2025-26. While also considering predictions from the North American Multi-Model Ensemble, the ENSO team believes uncertainty for the DJF season is high with La Niña (51% chance) slightly favored over ENSO-neutral (48% chance). La Niña is expected to remain weak (3-month average Niño-3.4 index value at or between -0.5°C and -0.9°C). A weak La Niña would be less likely to result in conventional winter impacts, though predictable signals could still influence the forecast guidance (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):

November 19, 2025 (updated mid-month)

The probability of La Niña has been predicted to be at 67% for November–January, easing to 53% for December–February 2025/26.

As of mid-November 2025, the equatorial Pacific is in a La Niña state, with sea surface temperatures in the Niño 3.4 region hovering near the La Niña threshold and continuing a gradual cooling trend. The IRI ENSO plume forecast places the probability of La Niña at 67% for November–January, easing to 53% for December–February 2025/26. From January–March onward, conditions begin shifting toward ENSO-neutral, which becomes the dominant outlook. Neutral probabilities rise to 63% at the start of the year and remain the leading state through the forecast period ending in July–September 2026. El Niño probabilities stay very low—below 10%—through March–May 2026, but gradually increase thereafter, reaching 16% in April–June, 27% in May–July, 32% in June–August, and 35% by July–September 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.

November 19, 2025 (updated mid-month)

The IRI ENSO prediction plume indicates a moderate likelihood of La Niña conditions during November–January 2025/26, with a 67% chance. The multimodel mean of statistical and dynamical models suggests La Niña conditions are likely to persist through December–February 2025/26 (53%). Thereafter, beginning in January–March 2026, 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 32% and 35% during the second quarter of 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.

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