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 high
tier 2 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Withdrawn from tracking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 / Withdrawn on 14 Oct 2026, before any use: the estimator's cap, anchored on a guessed base rate (5%), contradicted the official NOAA anchor (83%).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Withdrawn on 2026-10-14
78%Asturna estimate
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
- NOAA CPC's official 8 October 2026 ENSO discussion explicitly estimated an 83% probability that the October–December 2026 3-month RONI reaches at least +2.5°C [tier 1].
- Copernicus confirmed on 12 October 2026 that El Niño is continuing to strengthen toward record levels [tier 1].
- NOAA previously indicated heading into autumn that this event was tracking toward record intensity [tier 2, article 0].
What pushes it down
- Achieving a 3-month mean RONI of +2.5°C when the latest monthly Niño-3.4 reading is +2.1°C requires significant further warming across November and December, leaving little margin for sudden atmospheric decoupling or Kelvin wave dissipation [tier 1].
- RONI adjusts for background tropical warming, making a +2.5°C relative threshold harder to achieve than absolute ONI thresholds [tier 1].
- Seasonal dynamical models frequently exhibit a modest warm bias at multi-month lead times, warranting a discount from NOAA's 83% figure [tier 1].
What would move this number most
Whether tropical Pacific ocean-atmosphere coupling accelerates through November to lift the 3-month average to +2.5°C relative anomaly, or peaks earlier and falls short.
How this number is built
| Deadline | 2027-01-31 |
| Base rate | 3% |
| Best evidence | tier 2 · 1 article(s) used |
| Independent runs | 78 · 78 (spread 0 pts) |
| Confidence | high |
| Evidence cap | not triggered |
| Last revised | 2026-10-15 15:03 |
| Model | gemini-flash-latest |
Sources consulted
Probability history
2026-10-15 15:03 78% 8 article(s) on file · gemini-flash-latest
- What pushes it up. NOAA CPC's official 8 October 2026 ENSO discussion explicitly estimated an 83% probability that the October–December 2026 3-month RONI reaches at least +2.5°C [tier 1].
- What pushes it up. Copernicus confirmed on 12 October 2026 that El Niño is continuing to strengthen toward record levels [tier 1].
- What pushes it up. NOAA previously indicated heading into autumn that this event was tracking toward record intensity [tier 2, article 0].
- What pushes it down. Achieving a 3-month mean RONI of +2.5°C when the latest monthly Niño-3.4 reading is +2.1°C requires significant further warming across November and December, leaving little margin for sudden atmospheric decoupling or Kelvin wave dissipation [tier 1].
- What pushes it down. RONI adjusts for background tropical warming, making a +2.5°C relative threshold harder to achieve than absolute ONI thresholds [tier 1].
- What pushes it down. Seasonal dynamical models frequently exhibit a modest warm bias at multi-month lead times, warranting a discount from NOAA's 83% figure [tier 1].
- What would move this number most. Whether tropical Pacific ocean-atmosphere coupling accelerates through November to lift the 3-month average to +2.5°C relative anomaly, or peaks earlier and falls short.
2026-10-14 14:44 13% 6 article(s) on file · openai/gpt-oss-120b (Groq)
- 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.