ENSO Conditions and Coral Bleaching

(Update scheduled for the second Thursday of each month)

I) NOAA CPC Probabilistic Forecast
August 13, 2026

Alert Status: El Niño Advisory
(definitions)

El Niño is strengthening, with a greater than 90% chance of a very strong event during the Northern Hemisphere fall and winter 2026-27.

DIAGNOSTIC DISCUSSION:
[Available in various file formats]

El Niño strengthened over the past month, with sea surface temperature anomalies exceeding +2.0°C in the eastern equatorial Pacific. The July Niño index values were +1.4°C in Niño-3.4, +1.7°C in Niño-3, and +2.9°C in Niño-1+2. The equatorial subsurface temperature index (average from 180°-100°W) increased during July, reflecting a deeper-than-average thermocline. Subsurface temperature anomalies were significant, reaching +10.0°C at depth.

Low-level westerly wind anomalies and upper-level easterly wind anomalies extended from the western to east-central equatorial Pacific. Convection and rainfall were enhanced from the central to eastern Pacific and were suppressed over Indonesia. The traditional and equatorial Southern Oscillation indices were significantly negative, with values near 2 standard deviations during July. Collectively, the coupled ocean-atmosphere system reflected a strengthening El Niño.

The CPC Official ENSO outlook, which synthesizes multiple models from North America and abroad, indicates El Niño will continue to strengthen through the end of the year. During the October-December 2026 season, there is a 69% chance of a historic event that would exceed the strength of previous El Niño events dating back to 1950 (+2.5°C or more for a 3-month RONI value). With an event of this magnitude, the chances of experiencing impacts consistent with El Niño are larger, but they are not guaranteed (see CPC outlooks for probabilities of seasonal anomalies).

II) Frequently Used Figures
Click on the figures to access the web pages where these figures are described.

Other Relevant Information

Relative Ocean Niño Index (RONI) and Ocean Niño Index (ONI) (*** update on the 5th of each month ***)

Per NWS Public Information Statement 26-05, effectively February 1, 2026, the Relative Oceanic Niño index (RONI) is used for official monitoring and prediction of the El Niño-Southern Oscillation (ENSO) phenomenon. See more details here.

Journal Article: A Relative Sea Surface Temperature Index for Classifying ENSO Events

NOAA CPC's El Niño - Southern Oscillation (ENSO) resources webpage

The World Meteorological Organization (WMO) Climate Normals

El Niño Regions:

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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