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):

March 12, 2026 (updated early-month)

Alert Status:
La Niña Advisory / El Niño Watch
(definitions)

A transition from La Niña to ENSO-neutral is expected in the next month, with ENSO-neutral favored through May-July 2026 (55% chance). In June-August 2026, El Niño is likely to emerge (62% chance) and persist through at least the end of 2026.

DIAGNOSTIC DISCUSSION:

La Niña continued in February 2026, with below-average sea surface temperatures (SSTs) persisting in the east-central equatorial Pacific Ocean. The latest weekly Niño-3.4 index value was -0.5°C, with the westernmost (Niño-4) and easternmost (Niño-1+2) indices at -0.2°C and +0.6°C, respectively. The equatorial subsurface temperature index (average from 180°-100°W) continued to increase, reflecting the strengthening of above-average subsurface temperatures across the Pacific Ocean.

Over the east-central equatorial Pacific, low-level wind anomalies were easterly, while upper-level wind anomalies were westerly. Convection was suppressed over the Date Line and convection was enhanced over Indonesia. The traditional and equatorial Southern Oscillation indices were positive. Collectively, the coupled ocean-atmosphere system remained consistent with La Niña.

The North American Multi-Model Ensemble (NMME) average, including the NCEP CFSv2, points toward ENSO-neutral through the late Northern Hemisphere Spring 2026, with a transition to El Niño thereafter. Even though model forecasts are relatively less accurate this time of year, the increasing odds of El Niño are supported by the large amount of heat in the subsurface ocean and the expected weakening of the low-level trade winds. If El Niño forms, the potential strength remains very uncertain, with a 1-in-3 chance that it would be "strong" during October-December 2026 (Niño-3.4 ≥ +1.5°C).

... 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):

February 19, 2026 (updated mid-month)

the probability of La Niña at just 4% for Feb–Apr 2026 and shifts the odds in favor of ENSO-neutral conditions (about 96%) for the same period.

As of mid-February 2026, the equatorial Pacific is experiencing a declining La Niña conditions. The CCSR/IRI ENSO plume forecast places the probability of La Niña at just 4% for Feb–Apr 2026 and shifts the odds in favor of ENSO-neutral conditions (about 96%) for the same period. ENSO-neutral remains the dominant category through Mar-May (90%) and Apr-Jun (65%), while El Niño probabilities increase rapidly during same period. Starting in May-July, El Niño probabilities become higher than ENSO-neutral and remain in the range of 58% to 61%, with ENSO-neutral the second most likely outcome.

... 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.

February 19, 2026 (updated mid-month)

The CCSR/IRI ENSO prediction plume indicates a high likelihood of ENSO-neutral conditions during Feb–Apr 2026. The multimodel mean of statistical and dynamical models suggests highly likely situation for ENSO-neutral in Feb–Apr 2026 (96% chance), with ENSO-neutral conditions remaining the dominant category through Mar-May and Apr-Jun 2026. Over this period, the probability of El Niño development gradually increases from 9% in Mar-May to 35% by Apr–Jun 2026, and El Niño becomes the leading category during May-Jul and remain so during boreal summer and fall of 2026 (Jun to Dec), although probabilities remain in the low (between 58% to 61%). 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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