Global Meteorological Outlook for the 2026–2027 El Niño

As of late October 2026, the equatorial Pacific supports a strengthening El Niño across its standard indicators. NOAA CPC's ENSO Alert Status on October 8, 2026 was El Niño Advisory [S3], and the most recent Relative Oceanic Niño Index (RONI) value, 1.7°C for July–September 2026, is computed on ERSSTv6 after NCEI discontinued ERSSTv5 on 8/10/26, leaving weekly OISSTv2.1 data unaffected [S1]. The NOAA PSL El Niño Index Dashboard lists an MEI.v2 of 2.37 for September 2026 [S12], and equatorial Pacific upper-ocean heat anomalies are above average with a below-average thermocline slope index [S1].

The surface expression intensified through the fall. Most Niño indices increased in the past month, reaching +2.1°C in Niño-3.4, +3.0°C in Niño-3 and +3.9°C in Niño-1+2 [S17], while the equatorial subsurface temperature index (180°–100°W) was well above average, reflecting a deeper-than-average thermocline [S17]. Enhanced convection and rainfall persisted from the central to the eastern Pacific with suppressed anomalies over Indonesia [S17], and the event continues to intensify across the central and eastern equatorial Pacific [S6]. During the last four weeks, positive equatorial SST anomaly changes were observed in the east-central and eastern Pacific, the central Indian Ocean and the eastern Atlantic, with negative changes around Indonesia, the western Indian Ocean and the western Atlantic [S1].

Authoritative outlooks converge on a strong event. NOAA CPC's diagnostic discussion states that El Niño continues to strengthen, with a strong-to-very strong event likely through January–March 2027 at greater than an 83% chance [S2]. CPC assigns a 54% chance for September–November, 83% for October–December and 70% for November–January that a 3-month RONI value of +2.5°C or more would exceed the strength of every El Niño dating back to 1950 [S2]. The mid-October 2026 CCSR/IRI plume shows close agreement among 27 models (16 dynamical, 11 statistical) that conditions will strengthen further during 2026 and continue into early 2027 [S6], with the multimodel average near +3.5°C for Niño 3.4 in both OND and NDJ 2026 [S6], though individual models differ in peak magnitude [S6]. As of mid-June 2026, by comparison, IRI had assigned a 97–98% probability to persistence and dynamical models projected a 2.5–2.6°C peak [S5].

Physically, the event follows established warm-episode behavior: basin-wide equatorial Pacific upper-ocean (0–300 m) heat content is greatest prior to and during the early stages of a warm episode, and the thermocline slope is least during warm episodes [S1]. NASA/JPL altimetry shows Kelvin waves carrying high sea levels up and down the west coast of the Americas and, in trend-removed images, the 2026 event as large as or larger than 1997–98, with sea levels 15 to 20 cm below normal around Indonesia and northern Australia [S14]. By the sea-level indicator of Hamlington et al. (2019) without trend removal, however, the 1997 and 2015 events were much larger at the same time of year [S14]. The 2015/2016 event was itself far weaker than 1982/1983 and 1997/1998 in the Niño3 and Niño1+2 regions regardless of detrending [S11].

Expected teleconnections follow canonical patterns. During El Niño winters, tropical rainfall and atmospheric circulation changes often strengthen and shift the Pacific jet stream southward, increasing opportunities for winter storms across the southern United States; for Arizona and New Mexico this tilts the odds toward a wetter-than-average cool season without guaranteeing one [S13]. Storm-track position and persistence then determine where precipitation falls, and subtle shifts can direct the bulk north or south of the region [S13]. For eastern-Pacific ENSO, precipitation anomalies extend from the equatorial eastern to central Pacific, with opposite anomalies near Indonesia and Amazonia reflecting zonal shifts of the Walker circulation [S10]. CPC states that with an event of this magnitude, chances of impacts consistent with El Niño are larger, though not guaranteed [S2].

Near-term sectoral exposure is uneven. The 2026 U.S. crops will be substantially harvested before El Niño approaches its projected peak intensity, and the growing-season calendar largely insulates U.S. corn, wheat and soybeans from direct production risk [S5], with developing-phase effects on the Corn Belt considerably weaker and less spatially predictable than mature-phase effects [S5]. An appraisal of real-time ENSO status informs climate services for water supply, food security, health and public safety [S15], and the 2015/2016 event was marked by many environmental disasters consistent with an extreme El Niño, a relevant precedent [S11]. The 2026 event developed rapidly since spring, with above-average SSTs emerging in the far eastern equatorial Pacific in early February 2026 [S1][S13].

The equatorial Pacific reflects a strengthening El Niño across the standard SST indices. Most Niño indices increased in the past month, reaching +2.1°C in Niño-3.4, +3.0°C in Niño-3 and +3.9°C in Niño-1+2 [S17], and the most recent RONI value for July–September 2026 is 1.7°C [S1]. The NOAA PSL El Niño Index Dashboard lists an MEI.v2 of 2.37 for September 2026 [S12]. The traditional and equatorial Southern Oscillation indices were significantly negative, and collectively the coupled ocean-atmosphere system reflected a strengthening El Niño [S2], with atmospheric circulation anomalies over the equatorial Pacific consistent with El Niño [S1].

The subsurface ocean shows warm-episode structure. The equatorial subsurface temperature index (averaged 180°–100°W) was well above average, reflecting a deeper-than-average thermocline [S17], and the thermocline slope index is below average [S1]. During the last four weeks, positive equatorial SST anomaly changes were observed in the east-central and eastern Pacific Ocean, the central Indian Ocean and the eastern Atlantic Ocean [S1].

Convection and sea level corroborate the coupled state. Enhanced convection and rainfall persisted from the central to the eastern Pacific while anomalies remained suppressed over Indonesia [S17]. Detrended NASA/JPL altimetry images show the 2026 event as large as or larger than the 1997–98 event, with sea levels 15 to 20 cm below normal around Indonesia and northern Australia [S14], and the event continues to intensify across the central and eastern equatorial Pacific [S6]. CPC's alert status on October 8, 2026 remained El Niño Advisory [S3]. By the sea-level-based indicator of Hamlington et al. (2019) without trend removal, the 1997 and 2015 events were much larger at the same time of year [S14].

NOAA CPC's outlooks point to continued strengthening. The ENSO Diagnostic Discussion states that a strong-to-very strong El Niño is likely through January–March 2027 at greater than an 83% chance [S2], and the CPC Official ENSO outlook, which synthesizes multiple models from North America and abroad, indicates strengthening through the end of the year [S2]. CPC assesses the chance of a historic event exceeding all El Niño events dating back to 1950 (+2.5°C or more for a 3-month RONI value) at 54% for September–November, 83% for October–December and 70% for November–January [S2], and its Official RONI Outlook issued October 2026 presents forecast ranges for nine upcoming overlapping 3-month seasons [S20]. CPC's alert status on October 8, 2026 was El Niño Advisory [S3].

The CCSR/IRI plume agrees on strength and persistence. Its mid-October 2026 update shows close agreement among 27 models (16 dynamical and 11 statistical) that El Niño conditions will strengthen further during 2026 and continue into early 2027 [S6], with the combined multimodel average forecasting the Niño 3.4 index near +3.5°C in both OND and NDJ 2026 [S6]. Individual models differ in the magnitude of the peak, while the overall signal points to a very strong event lasting well beyond fall 2026 and into spring 2027 [S6]. IRI cautions that the ensemble mean is only a best single guess with a substantial uncertainty distribution [S4], whose width derives from the historical skill of model hindcasts from 1982 to present for each start and lead time [S19].

Vintage and process explain residual differences. As of mid-June 2026, IRI assigned a 97–98% probability to El Niño persisting through the remainder of 2026, and dynamical models then projected a peak Niño3.4 anomaly near 2.5–2.6°C, which would rank among the strongest events on record [S5]; the October plume is the more current vintage. Human forecasters may disagree to some degree with the models, which may have known biases, and the models are not run at the same time the forecasters make their assessment, so starting ENSO conditions may differ slightly [S4]. The 2026 event developed rapidly since last spring and is expected to continue strengthening through the fall [S13].

By CPC's standard metric, the event has not yet reached record strength but is forecast to approach it. The most recent RONI value (July–September 2026) is 1.7°C [S1], while CPC defines a historic event as a 3-month RONI of +2.5°C or more exceeding the strength of previous El Niño events dating back to 1950, with chances of 54% for September–November, 83% for October–December and 70% for November–January [S2]. CPC's October 2026 discussion summarizes a strong-to-very strong El Niño as likely through January–March 2027 at greater than an 83% chance [S2], under an El Niño Advisory issued October 8, 2026 [S3]. NOAA PSL reports an MEI.v2 of 2.37 for September 2026 [S12].

Model projections are more extreme than current observations. The mid-October 2026 CCSR/IRI plume shows 27 models (16 dynamical, 11 statistical) in close agreement on strengthening into early 2027 [S6], with the multimodel average near +3.5°C for Niño 3.4 in OND and NDJ 2026 and a tight spread through MAM 2027 [S6]; individual models differ in peak magnitude [S6]. As of mid-June 2026, dynamical models projected a 2.5–2.6°C peak, which would rank among the strongest events on record [S5].

Benchmark comparisons depend on indicator choice. NASA/JPL altimetry reports Kelvin waves carrying high sea levels along the Americas and the 2026 event as large as or larger than the 1997–98 event at this point, with sea levels 15 to 20 cm below normal around Indonesia and northern Australia [S14]. Yet using the sea-level-based indicator of Hamlington et al. (2019), the 1997 and 2015 events were much larger at the same time of year [S14].

Whether "extreme" applies is partly definitional. The peer-reviewed literature notes that how an extreme El Niño is defined remains unresolved, and it is not yet clear what other variables could be used in event characterization [S11]; the short observational record means knowledge of an extreme El Niño has been based only on the 1982/1983 and 1997/1998 events [S11]. The 2015/2016 event was marked by many environmental disasters consistent with an extreme El Niño [S11], yet in the Niño3 and Niño1+2 regions its warm SST anomaly was far weaker than in 1982/1983 and 1997/1998 regardless of detrending [S11], illustrating how region and index choice affect rankings.

The preconditioning signature matches canonical warm-episode dynamics. The basin-wide equatorial Pacific upper-ocean (0–300 m) heat content is greatest prior to and during the early stages of a Pacific warm episode, and the slope of the oceanic thermocline is least during warm episodes [S1]. Currently, equatorial Pacific upper-ocean heat anomalies are above average and the thermocline slope index is below average [S1], consistent with that established evolution.

The 2026 development began from a cool base. Through February 2026, below-average SSTs were evident across most of the equatorial Pacific Ocean, and beginning in early February 2026 above-average SSTs emerged in the far eastern equatorial Pacific [S1]. The traditional and equatorial Southern Oscillation indices were significantly negative, and collectively the coupled ocean-atmosphere system reflected a strengthening El Niño [S2], with atmospheric circulation anomalies over the equatorial Pacific consistent with El Niño [S1]. NASA/JPL altimetry shows Kelvin waves carrying high sea levels up and down the west coast of the Americas [S14].

Event-type diagnostics can be framed from documented precipitation patterns. For eastern-Pacific (EP) ENSO, precipitation anomalies extend from the equatorial eastern to central Pacific, where the largest SST anomalies are located [S10], with opposite precipitation anomalies near the Indonesia and Amazon regions, reflecting zonal shifts of the Pacific Walker circulation [S10]. Observed in 2026, enhanced convection persisted from the central to the eastern Pacific with suppressed anomalies over Indonesia [S17], and Niño-1+2 reached +3.9°C against +2.1°C in Niño-3.4 [S17], though no formal typing of the event is issued.

The best-documented teleconnection for the coming seasons is over North America. During El Niño winters, changes in tropical rainfall and atmospheric circulation often strengthen and shift the Pacific jet stream southward, increasing opportunities for winter storms across the southern United States [S13]. For Arizona and New Mexico, El Niño tilts the odds toward a wetter-than-average cool season, but it does not guarantee a wet winter [S13]. Storm-track position and persistence ultimately determine where storms travel and how much precipitation falls, and even subtle shifts can direct the bulk of precipitation north or south of the Southwest, such as between northern and southern Arizona [S13].

Tropical teleconnections follow the documented ENSO pattern. For eastern-Pacific ENSO, precipitation anomalies extend from the equatorial eastern to central Pacific, where the largest SST anomalies are located, with opposite anomalies near the Indonesia and Amazon regions, reflecting zonal shifts of the Pacific Walker circulation [S10]. CPC states that with an event of this magnitude, the chances of experiencing impacts consistent with El Niño are larger, though not guaranteed [S2].

Timing tempers U.S. growing-season effects. The 2026 U.S. crops will be substantially harvested before El Niño approaches its projected peak intensity, and developing-phase ENSO effects on the U.S. Corn Belt are considerably weaker and less spatially predictable than mature-phase effects [S5].

Agriculture faces limited direct U.S. exposure. The growing-season calendar largely insulates U.S. corn, wheat and soybeans from direct El Niño production risk [S5], because the 2026 U.S. crops will be substantially harvested before El Niño approaches its projected peak intensity [S5]. Developing-phase effects on the U.S. Corn Belt are considerably weaker and less spatially predictable than mature-phase effects [S5].

Water resources and storm exposure center on the southern United States. During El Niño winters, tropical rainfall and circulation changes often strengthen and shift the Pacific jet stream southward, increasing opportunities for winter storms across the southern United States [S13], and for Arizona and New Mexico El Niño tilts the odds toward a wetter-than-average cool season without guaranteeing a wet winter [S13]. Even subtle storm-track shifts can direct the bulk of precipitation north or south of the Southwest or produce very different outcomes within it [S13].

Broader sectoral framing is general rather than event-specific. CPC states that with an event of this magnitude, the chances of experiencing impacts consistent with El Niño are larger, though not guaranteed [S2]. An appraisal of the real-time ENSO status is important for climate services that inform societal responses and trigger policy actions for water supply, food security, health and public safety [S15]. The 2015/2016 El Niño was marked by many environmental disasters consistent with what is expected for an extreme El Niño, providing a relevant precedent [S11].

The principal scenario fork is peak magnitude. CPC's baseline is a strong-to-very strong El Niño through January–March 2027 at greater than an 83% chance, with chances of a historic event, a 3-month RONI of +2.5°C or more exceeding all events since 1950, at 54% for September–November, 83% for October–December and 70% for November–January [S2]. The most recent observed RONI, 1.7°C for July–September 2026 [S1], shows the historic threshold not yet reached. CPC states that with an event of this magnitude, the chances of experiencing impacts consistent with El Niño are larger, though not guaranteed [S2].

Whether the event ranks as extreme is sensitive to indicator construction. How an extreme El Niño is defined remains an unresolved issue, and it is not yet clear what other variables could be used in event characterization [S11]; the short observational record means knowledge of an extreme El Niño has been based only on the 1982/1983 and 1997/1998 events [S11]. In the Niño3 and Niño1+2 regions, the 2015/2016 warm anomaly was far weaker than in 1982/1983 and 1997/1998 regardless of detrending [S11], and by the sea-level indicator of Hamlington et al. (2019) the 1997 and 2015 events were much larger at the same time of year [S14], so index and region choice materially change the comparison.

Observable indicators discriminate among these paths: the 3-month RONI, now computed on ERSSTv6 after the 8/10/26 discontinuation of ERSSTv5, with weekly OISSTv2.1 data unaffected [S1]; upper-ocean heat anomalies, currently above average, and the thermocline slope index, currently below average [S1]; and midlatitude storm-track position and persistence, which determine where storms travel and how much precipitation falls, with subtle shifts able to direct the bulk north or south of the Southwest [S13]. For Arizona and New Mexico, the wetter cool-season odds are tilted but not guaranteed [S13]. A post-peak transition scenario has historical precedent: the 1998/1999 extreme La Niña immediately followed an extreme El Niño [S11].

Authoritative diagnostics are distinguishable by institutional mandate, methodology and quantified uncertainty. The CPC ENSO Diagnostic Discussion is a consolidated effort of NOAA, NOAA's National Weather Service and their funded institutions [S2], and the CPC Official ENSO outlook synthesizes multiple models from North America and abroad [S2]. Primary monitoring products carry explicit methods: the OOPC Niño3.4 surface index uses the Reynolds OIv2 SST analysis, updated weekly with the last update on 27-SEP-2026, with anomalies relative to a 1991–2020 climatological seasonal cycle [S8] and a quantified uncertainty of 0.05835°C over 1982–present [S8]. GODAS assimilates temperature profiles from TAO moorings, Argo floats and XBTs against a 1981–2010 base period [S7], and the MEI combines oceanic and atmospheric variables into a single index serving water-supply, food-security, health and public-safety climate services [S15].

Secondary commentary is identified by authorship and forecast vintage. The Purdue vegetable-oil-market analysis is authored by Ken Foster, Bernhard Dalheimer and David Ubilava [S5] and relies on the mid-June 2026 IRI assessment, when IRI assigned a 97–98% persistence probability and dynamical models projected a 2.5–2.6°C peak [S5]. Publication dates are verifiable from documented schedules: CPC updates ENSO conditions weekly, publishes a probabilistic strength forecast, and issues the Diagnostics Discussion on the second Thursday of each month, with the next scheduled for 12 November 2026 [S2]. The mid-October 2026 CCSR/IRI plume is the more current vintage, and the IRI Quick Look charts are updated twice monthly, about a week apart, with the CPC forecast starting on the previous season and the CCSR/IRI forecast on the current season [S4].

Where outlooks conflict or update at different times, documented reconciliation factors apply. IRI notes that human forecasters may disagree with the models because the models may have known biases and are not run at the same time the forecasters make their assessment, so the starting ENSO conditions may differ slightly [S4]. The ensemble mean is only a best single guess, with percentile plots quantifying the probability of the Niño3.4 anomaly exceeding or falling below critical values [S4], and distribution width derives from hindcast skill from 1982 to present for each start and lead time [S19].

Index conventions must also be held explicit when comparing products. RONI switched from ERSSTv5 to ERSSTv6 on 8/10/26 while weekly OISSTv2.1 data remained unaffected, with the July–September 2026 RONI at 1.7°C [S1]; NASA/JPL's sea-level comparisons depend on whether the long-term trend is removed, since by the Hamlington et al. (2019) indicator the 1997 and 2015 events were much larger at the same time of year [S14]. CPC's classification thresholds anchor event definitions: monthly relative Niño3.4 departures meeting or exceeding +0.5°C with consistent atmospheric features, exceeded for at least 5 consecutive overlapping 3-month seasons for a full-fledged episode, with qualifying anomalies forecast to persist for 3 consecutive months [S1]. CPC's October vintage assigns the historic-event probabilities of 54%, 83% and 70% for the three overlapping seasons [S2].

Background warming materially affects how the 2026 event is ranked against prior events. NASA/JPL's comparison images have the long-term trend removed to compute the displays [S14], and in those trend-removed images the 2026 event is as large as or larger than the 1997–98 event [S14]. The SSH-based El Niño index of Hamlington et al. (2019), which has not had the long-term warming effect removed, showed the current event similar in strength to the 1997–98 event in mid-September [S14], and by that sea-level indicator the 1997 and 2015 events were much larger at the same time of year [S14]. Apparent extremity therefore depends on baseline and detrending treatment.

A concurrent non-ENSO driver is the Indian Ocean Dipole. In the CCSR/IRI probabilistic IOD forecast, positive IOD conditions become strongly dominant in October 2026 with probabilities approaching 100%, and this dominance is expected to persist through November and December 2026 with probabilities of 97% and 74%, respectively [S4]. On the ENSO side, CPC's RONI-based chances of a historic event, 54% for September–November, 83% for October–December and 70% for November–January, frame the strength uncertainty against this background [S2].