Will NOAA's Climate Prediction Center report a 3-month RONI of at least +2.5°C for October–December 2026?

deadline 2027-01-31 confidence medium tier 4 evidence

Withdrawn from tracking

Reason: formulation error — Retirée le 14 oct. 2026, avant tout usage : le plafond de l'estimateur, ancré sur un taux de base deviné (5 %), contredisait l'ancrage officiel NOAA (83 %). Sera réadmise après correction. / Withdrawn on 14 Oct 2026, before any use: the estimator's cap, anchored on a guessed base rate (5%), contradicted the official NOAA anchor (83%). To be readmitted after the fix.

Withdrawn on 2026-10-14

13%PolySignal estimate

⚠ Evidence cap applied: the model proposed 78%, brought back to 13% for lack of sources solid enough to justify the departure from the base rate.

Resolution criterion

Yes if the 3-month Relative Oceanic Niño Index (RONI) for October–December 2026, as published by NOAA's Climate Prediction Center (its RONI table or its ENSO diagnostic discussion), is +2.5°C or higher, as available on or before 31 January 2027. A value below +2.5°C, or no published value by that date, resolves No.

Verified starting state

NOAA CPC's ENSO discussion of 8 October 2026: El Niño Advisory in effect, latest Niño-3.4 at +2.1°C, and a stated 83% probability of a historic event (3-month RONI of +2.5°C or more) for October–December 2026, 70% for November–January. The next update is due on 12 November 2026. Copernicus (12 October 2026) says El Niño is strengthening and likely to be one of the strongest on record.

What pushes it up

Official NOAA ENSO discussion (tier 1) states an 83% probability of a 3‑month RONI ≥+2.5°C for Oct‑Dec 2026.

What pushes it down

The forecast is still an announcement and could be revised downward in the next update; historically such high RONI values are rare.

What would move this number most

The result of the upcoming NOAA CPC update (12 Nov 2026) and the actual observed RONI value.

How this number is built

Deadline	2027-01-31
Base rate	5%
Best evidence	tier 4 · 0 article(s) used
Independent runs	13 · 13 (spread 0 pts)
Confidence	medium
Evidence cap	applied: 78% brought back to 13%
Last revised	2026-10-14 14:44
Model	openai/gpt-oss-120b (Groq)