Will the peak RONI value during the NDJ 2026-27 season be at least 2.5°C?

- [2026-09-10] NOAA CPC's ENSO Diagnostic Discussion (issued 10 Sept 2026, current advisory) states: "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 (+2.5C or more for a 3-month RONI value)." This directly targets the OND/NDJ window relevant to this contract. https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.pdf - [2026-09-10] The same discussion reports monthly SST anomalies for August 2026: the official ENSO outlook for the Niño-3.4 relative sea surface temperature index (RONI), figure updated 10 September 2026 , alongside observed Niño-3, Niño-1+2 readings well above historic thresholds (Niño-3.4 +1.8°C, Niño-3 +2.5°C, Niño-1+2 +3.4°C in August). https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.shtml - [2026-09-10] CPC's ENSO Alert Status remains "El Niño Advisory," with the synopsis stating "El Niño is strengthening, with a greater than 90% chance of a very strong event during the Northern Hemisphere fall and winter 2026-27." https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.shtml - [2026-09-28] CPC's weekly "ENSO: Recent Evolution, Current Status and Predictions" update (28 Sept 2026) confirms El Niño is present and strengthening, with sea surface temperatures above average across the east-central and eastern Pacific and atmospheric anomalies consistent with El Niño. https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf - [2026-09-21] IRI's CCSR/IRI ENSO update (published 21 Sept 2026) reports the Niño 3.4 seasonal mean reached +2.03°C for June–August 2026, the August monthly value rose to +2.52°C, and the latest weekly value (centered 16 Sept 2026) hit +3.0°C. https://iri.columbia.edu/our-expertise/climate/forecasts/enso/current/ - [2026-09-21] The same IRI update states all 22 models in the plume forecast a "very strong" El Niño (≥+2.0°C) from SON 2026 through DJF 2026-27, with a majority projecting Niño3.4 values that could reach or exceed +3.0°C, and El Niño probability at 100% from SON 2026 through FMA 2027. https://iri.columbia.edu/our-expertise/climate/forecasts/enso/current/ - [2026-09-21] IRI notes subsurface ocean heat remains exceptional, with the Niño 1+2 index persistently above +4°C for six weeks, providing a large energy reservoir for continued surface warming into boreal fall/winter. https://iri.columbia.edu/our-expertise/climate/forecasts/enso/current/ - [2026-09-16] The 30-day Southern Oscillation Index through 16 Sept 2026 remained strongly negative at −20.1, and the Equatorial SOI reached −2.5 in August 2026, both consistent with a strongly coupled, strengthening El Niño. https://iri.columbia.edu/our-expertise/climate/forecasts/enso/current/ - [2026-09-03] The WMO El Niño Update (3 Sept 2026) puts the likelihood El Niño persists through Feb 2027 near 100%, forecasting the event to strengthen "to a very strong intensity before peaking towards the end of this year," calling this its most unequivocal ENSO forecast on record. https://www.elninolive.com/el-nino-2026 - [2026-09-01] Historical context from CPC/RONI methodology background: NOAA's historical RONI record shows the two strongest prior El Niño peaks (1997/98 and 2015/16) both topped out at +2.3°C, making a ≥+2.5°C RONI value an unprecedented (record) reading if it occurs. https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso/roni/pdf/roni-info-may-2026.pdf - [2026-10-08] CPC's next scheduled ENSO Diagnostic Discussion (with updated RONI figures and probabilities) is due 8 October 2026, before the NDJ 2026-27 season's official/final RONI value would be published. https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.shtml - [2026-09-29] A third-party tracker reports current (non-CPC-final) readings: RONI for JJA 2026 at +1.4°C, while the conventional weekly Niño 3.4 anomaly for the week of 23 Sept 2026 runs +3.1°C, illustrating the gap between raw Niño3.4 anomaly and the smoothed/relative RONI metric that will determine the contract outcome. https://www.elninolive.com/map BOTTOM LINE: As of late September 2026, El Niño is strong and strengthening, and NOAA CPC's own official forecast (10 Sept 2026, next update due 8 Oct 2026) assigns a 75% chance that the OND 2026 3-month RONI value reaches +2.5°C or higher — a threshold no prior event has reached in the RONI record — with IRI/CCSR model consensus, weekly Niño3.4 readings near +3.0°C, and deep subsurface warmth all reinforcing that a historically extreme, "very strong" event is underway heading into NDJ 2026-27. NOT FOUND: The specific, CPC-published "final" RONI numeric value for any season in 2026 (only forecast/probability figures and preliminary monthly Niño-index values were available); the exact NDJ 2026-27 RONI probability breakdown (CPC's 75% figure is specifically for OND 2026, not NDJ); and any RONI table entry explicitly marked "final" for a 2026 season, since final designations lag by design.

- [2026-09-10] NOAA CPC's official ENSO Diagnostic Discussion states: "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 (+2.5C or more for a 3-month RONI value)." This is CPC's own probabilistic base rate for the RONI≥2.5°C threshold, one season prior to NDJ. Source: https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.pdf - [2026-09-10] The same discussion frames confidence as: "In summary, El Niño is strengthening, with a greater than 90% chance of a very strong event during the Northern Hemisphere fall and winter 2026-27." "Very strong" (RONI ≥2.0°C) is a lower bar than the 2.5°C threshold in this contract. Source: https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.pdf - [2026-09-10 outlook] CPC's official RONI outlook chart (Fig. 6) shows the ensemble mean forecast rising through ASO/SON/OND and peaking near OND–NDJ at roughly the high-2°C range (with a 25–75% "likely" band straddling 2.5°C for OND/NDJ), confirming the season in question sits at or very near the model's forecast peak. Source: https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.pdf (Fig. 6) - [historical base rate] Reference-class review of RONI since 1950 shows no prior three-month RONI value has ever reached +2.5°C: "On ONI, the raw Niño 3.4 anomaly, 2015-16 is the strongest since 1950 at roughly +2.6°C for NDJ... On RONI... the 2015-16 peak is +2.4°C for NDJ 2015 and the record holder changes: Hausfather's analysis puts 1982-83 ahead." The 1982-83 event is generally cited as the RONI record-holder at about +2.4°C, still below 2.5°C. Source: https://iamelnino.com/enso-historical-table - [historical base rate, corroborating] An independent ENSO tracker states "Strongest events on record ranked by peak RONI (1982-83 holds the +2.5°C record)" — even the highest cited estimate for the prior record (1982-83) is right at, not clearly above, 2.5°C, underscoring that reaching/exceeding this level in NDJ would be unprecedented or at the very edge of the historical envelope. Source: https://4billionyearson.org/climate/enso - [2026-09 real-time evidence, not base rate but relevant to trend] Carbon Brief's analysis notes "RONI stood at around 2.5C in mid-September, some 0.7C below the 1982 record. However, that record was set in late December, at the peak of the event." and that "The 1982-83, 1997-98 and 2015-16 events added between 0.5C and 1.9C to their RONI values between mid-September and their peaks," implying further increases are typical between September and the NDJ/DJF peak. Source: https://www.carbonbrief.org/analysis-super-el-nino-reaches-remarkable-all-time-record - [2026-09-10, sibling contract/officiial threshold] A secondary meteorology summary independently restates CPC's own framing: "NOAA's current forecast indicates a 75% probability that the October-December 2026 season reaches a historic El Niño strength, defined as a three-month RONI value of at least +2.5°C, which would exceed the strength of previous events dating back to 1950." Source: https://praedictix.com/the-historic-record-warm-super-el-nino-is-here/ - [independent model estimate, 2026-09-07] A private multi-model composite (Treefera) reported "Treefera's multi-model RONI composite at +3.24°C for the November-January peak, ahead of every past event since 1950, including 1982-83 (+2.36°C), 1997-98 (+2.28°C) and 2015-16 (+2.25°C)" , a more aggressive estimate than CPC's official outlook, but also noting "NOAA's official RONI outlook of 13 August 2026, at +2.23°C, ranks it second behind 1982-83." This shows dispersion between official CPC and private model-based estimates. Source: https://www.treefera.com/blog/from-ocean-to-origin-how-treefera-turns-a-pacific-signal-into-field-level-risk - [track record note] CPC's ENSO probability forecasts and strength-category outlooks (updated monthly since the RONI adoption in Feb 2026) are the closest thing to an institutional track record for this exact index; RONI is too new (adopted 2026) to have an independently verified forecast-skill history at the 2.5°C extreme-tail level, so "base rate of CPC being right at this exact threshold" cannot be assessed from historical CPC RONI forecasts. BOTTOM LINE: The reference class (RONI since 1950) has never recorded a three-month value ≥2.5°C — the closest historical analog (1982-83) topped out at roughly +2.4°C — so a NDJ 2026-27 peak at or above 2.5°C would be an unprecedented, record-setting outcome; however, NOAA CPC's own September 2026 official outlook already assigns a 75% probability to a comparable (OND) season reaching that threshold, and independent trackers/models show mid-to-late-September RONI values already near or above 2.5°C with typical additional seasonal increases still to come into NDJ, suggesting the current event is tracking well outside historical norms and toward, not away from, the threshold. NOT FOUND: An official CPC RONI probability figure specifically for the NDJ (rather than OND) season at the 2.5°C threshold; the actual final NDJ RONI value (not yet observed, as NDJ 2026 has not concluded); a verified historical track record of CPC's RONI-based seasonal outlooks' hit rate at extreme thresholds (index too new, adopted Feb 2026).

YES means: NOAA CPC's official RONI table records a peak three-month value of at least +2.5°C for a period within the NDJ 2026-27 season (i.e., the season's most extreme reading, once finalized, meets or exceeds the historic +2.5°C threshold). - [2026-09-27] Australia's Bureau of Meteorology reports the latest relative Niño3.4 index value for the week ending 27 September 2026 is +2.72°C, the second-highest value on record in the bureau's weekly SST data (starting 2008), behind only +2.76°C for the week ending 22 November 2015 . This is a different (BOM) relative index, not CPC's RONI, but it is a fresh, high-confidence, near-real-time observation showing the event already exceeding 2.5°C on a comparable relative-anomaly basis weeks before the NDJ season's midpoint. Source: https://www.bom.gov.au/climate/enso/ - [2026-09-27] BOM's own model synthesis states relative-Niño3.4 values are forecast to reach levels above the warmest observed since reliable records began in 1950, with the majority of models indicating a peak value above +3.0°C , corroborating (from an agency independent of CPC/IRI) that the anticipated peak is not marginal but comfortably above the 2.5°C bar. - [2026-09-27] BOM confirms the atmospheric coupling remains strong and record-like: the Southern Oscillation Index remains strongly negative, with the latest 30-day SOI to 27 September 2026 at –20.5, well below the El Niño threshold of –7 , indicating the ocean-atmosphere feedback needed to sustain/strengthen the event into NDJ is intact. - [2026-09-27] A Meteored/IRI-sourced analysis of the September IRI model plume (published 27 Sept, referencing the 21 Sept IRI update) reports the average of the dynamic models indicates the peak of the event is expected to occur between October 2026 and January 2027, with anomalies close to +3.5°C, while the average of all models points to a maximum of around +3.4°C . This directly brackets the NDJ 2026-27 window with forecast peak values roughly a full degree above the 2.5°C contract threshold. - [2026-09-27] The same analysis quantifies month-over-month model tightening: the convergence has raised the overall average of the forecasts, which increased from around +3.1°C in August to approximately +3.4°C in the September update , i.e., forecasts are moving up, not down, as the season approaches. - [2026-09-21] Carbon Brief's ONI-convention analysis states the observed monthly value is already historically extreme: the latest full calendar month for which data is available – August 2026 – had a Niño 3.4 anomaly of around 2.45°C, higher than the peak of every prior El Niño event on record except 2015-16 (2.75°C) and 1877-78 (~2.7°C) , and further notes the 1982-83, 1997-98 and 2015-16 events added between 0.5°C and 1.9°C to their RONI values between mid-September and their peaks , implying substantial further seasonal increase is typical and expected into the NDJ window. - [2026-07-13] Climate scientist Zeke Hausfather's model synthesis (Climate Brink) gives an explicit RONI-specific probability: models give a ~91% chance of a record peak in Niño 3.4 terms and ~77% in RONI terms this year , an independent quantitative estimate broadly consistent with (and reinforcing) CPC's own 75% OND figure, from a source using multiple dynamical/statistical model ensembles rather than CPC's outlook alone. - [2026-09-10, WMO] The Global Seasonal Climate Update for SON 2026 forecasts the seasonal average Niño 3.4 SST ensemble mean anomaly to reach approximately 3.6°C during SON 2026, with the intensification trajectory peaking in November-December — a third independent multi-model source (WMO's Global Producing Centres) placing the peak squarely in the NDJ window at a magnitude far above 2.5°C. - [2026 methodology note] Even under the RONI methodology's stricter historical ranking, the current event does not need to merely tie the record but comfortably beat it: multiple trackers converge that the record event in RONI terms is 1982-83 (a peak monthly value of 2.69°C) , meaning the 2.5°C contract threshold sits below even the historical RONI record, not above it — the bar for a YES resolution is lower than the record the models already expect to be broken. BOTTOM LINE: Multiple independent, current (mid-to-late September 2026) primary and near-primary sources — BOM's weekly relative index (+2.72°C, 27 Sept), the IRI/Meteored dynamical-model average (~+3.4–3.5°C peak forecast for Oct 2026–Jan 2027), WMO's SON 2026 multi-model mean (+3.6°C), and Hausfather's ~77% RONI-record probability — all converge on a NDJ 2026-27 peak well above the 2.5°C threshold, with forecasts trending upward each month rather than down, making the YES case for this contract unusually well-supported for a "record-breaking" threshold. NOT FOUND: No source yet shows a CPC-designated "final" RONI table entry for any 2026 season (the metric needed to formally resolve the contract); no NDJ-specific (as opposed to OND or SON) CPC probability figure at the 2.5°C threshold.

YES means: the NDJ (Nov–Dec–Jan) 2026-27 RONI value, once published as final by NOAA CPC, reaches at least +2.5°C — a level no three-month RONI period has ever recorded since 1950. - [2026-08-18] CPC's official August RONI outlook, as reported by a meteorology outlet citing the CPC assessment, put the October–December 2026 average at +2.66°C but showed the forecast **declining** to +2.23°C for December–February, with the OND middle-50% spread running only +2.37°C to +2.95°C — meaning even CPC's own central tendency, once averaged into the NDJ window that sits between these two seasons, is not safely above 2.5°C. https://www.gazetaexpress.com/en/parashikohet-qe-el-nino-te-arrije-nje-force-historike-perpara-dimrit-2026-27/ - [2026-08-18] The same source states that CPC's probability of a "very strong" event was 90% for November–January but only 70% for December–February, confirming CPC's own model output already shows probability and magnitude fading as the window shifts from OND toward DJF — exactly the seasons flanking NDJ. https://www.gazetaexpress.com/en/parashikohet-qe-el-nino-te-arrije-nje-force-historike-perpara-dimrit-2026-27/ - [2026-09-21] ASEAN's ASMC seasonal outlook (updated 21 Sept 2026) states model outlooks predict El Niño conditions to continue strengthening only until October–November 2026, with most models beginning to weaken in December 2026–January 2027 — i.e., the models' own peak timing sits before, not within, the back half of the NDJ window. https://asmc.asean.org/asmc-el-nino/ - [2026-09-21] Carbon Brief's analysis explicitly cautions that the RONI methodology, which subtracts tropical-mean SST anomalies to control for background climate warming, "can also diminish the apparent strength of strong El Niño events" relative to the raw Niño3.4 anomaly — a structural dampening effect that works against reaching the 2.5°C threshold even as raw indices break records. https://www.carbonbrief.org/analysis-super-el-nino-reaches-remarkable-all-time-record - [2026-09-21] The same analysis notes that "no seasonal forecast system has ever been verified against an event of this size, because none has ever occurred," and that real-world August observations came in about 0.3°C **below** what the models had forecast for that month — a documented recent over-forecasting bias in exactly the models underpinning the 75% CPC probability. https://www.carbonbrief.org/analysis-super-el-nino-reaches-remarkable-all-time-record - [2026-09-21] Carbon Brief further reports that daily RONI in mid-September stood at 2.5°C, "some 0.7C below the 1982 record," and that historically the three biggest events (1982-83, 1997-98, 2015-16) added only "between 0.5C and 1.9C" from mid-September to their eventual peak — a wide historical range whose low end (+0.5°C) would leave the 3-month NDJ average well short of an unprecedented, sustained ≥2.5°C reading once monthly noise is smoothed into a seasonal mean. https://www.carbonbrief.org/analysis-super-el-nino-reaches-remarkable-all-time-record - [2026-09-10] Even CPC's own headline number is explicitly for the October–December season, not NDJ; nowhere in the 10 Sept discussion is an NDJ-specific ≥2.5°C probability stated, leaving a residual ~25% (by CPC's own OND figure) or higher chance of falling short once the later, cooler tail of the window (January) is included in the average. https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.pdf - [2026-09-07] A private multi-model composite (Treefera, 7 Sept 2026) shows dispersion between official CPC (+2.23°C RONI outlook as of 13 Aug) and more aggressive private estimates (+3.24°C) for the November–January peak — a nearly 1°C spread among credible forecasters underscores how far from settled the eventual NDJ value is, and that CPC's own institutional number has, at times, sat noticeably below the 2.5°C bar. https://www.treefera.com/blog/from-ocean-to-origin-how-treefera-turns-a-pacific-signal-into-field-level-risk - [Resolution-technicality] The contract requires a value "designated as final (non-preliminary)" in the CPC RONI table; CPC's routine practice is to carry monthly/seasonal RONI values as preliminary for some period before finalizing them, so even if provisional NDJ readings appear ≥2.5°C soon after the season ends, the contract's own rules permit resolution only once CPC affirmatively marks that specific NDJ entry "final," creating a structural lag/inertia risk independent of the underlying climate signal. BOTTOM LINE: The strongest NO case rests on CPC's own numbers showing the RONI seasonal average is forecast to crest in OND and decline into DJF (with NDJ sitting between a +2.66°C and a +2.23°C central estimate), on El Niño peak-timing outlooks (ASMC, IRI) that put the modeled peak in October–November rather than centered on NDJ, on RONI's methodological tendency to run cooler than raw Niño3.4 anomalies, and on a documented recent model over-forecast bias — all of which leave real room for the NDJ three-month average to land below the unprecedented +2.5°C mark even amid a record-strength event. NOT FOUND: An NDJ-specific CPC probability figure for the ≥2.5°C RONI threshold (only OND 75%/69% and DJF ~70%/very-strong figures were located); any CPC RONI table entry for 2026 seasons explicitly marked "final"; and a precise, sourced definition of how many months CPC typically carries a RONI season as "preliminary" before finalizing it.