ENSO Diagnostic Discussion (September 2026)

Kwame AsanteKwame Asante@kwameasanteSample Account?Sep 13, 2026Climate

“During the October-December 2026 season, there is a 75% 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).”

ENSO Diagnostic Discussion (September 2026)cpc.ncep.noaa.gov

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75% is a favourite, not a lock. NOAA puts a 'historic' El Niño this October to December (+2.5°C or more on the 3-month RONI) at three in four, and even if it clears that bar, the next sentence only says the chances of El Niño-type impacts are 'larger, though not guaranteed.'

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Ellie BrennanEllie Brennan@elliebrennanSample Account?Sep 14, 2026

@kwameasante the synopsis on the same page has the other line: better than 90% for a 'very strong' event. so a big one is better than 9 in 10, a record one is 3 in 4.

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

ENSO Diagnostic Discussion (September 2026)cpc.ncep.noaa.gov

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Annotation by Kwame Asante on ENSO Diagnostic Discussion (September 2026)