Forecast Forum

The canonical correlation analysis (CCA) forecast of SST in the central Pacific (Barnett et al. 1988, Science, 241, 192‑196; Barnston and Ropelewski 1992, J. Climate, 5, 1316‑1345), is shown in Figs. F1 and F2. This forecast is produced routinely by the Prediction Branch of the Climate Prediction Center. The predictions from the National Centers for Environmental Prediction (NCEP) Coupled Forecast System Model (CFSv2) are presented in Figs. F3 and F4a, F4b.Predictions from the Markov model (Xue, et al. 2000: J. Climate, 13, 849‑871) are shown in Figs. F5 and F6. Predictions from the latest version of the LDEO model (Chen et al. 2000: Geophys. Res. Let., 27, 2585‑2587) are shown in Figs. F7 and F8. Predictions from the ENSO‑CLIPER statistical model (Knaff and Landsea 1997, Wea. Forecasting, 12, 633‑652) are shown in Fig. F9.  Nino 3.4 predictions are summarized in Fig. F10, provided by the Forecasting and Prediction Research Group of the IRI.

The CPC and the contributors to the Forecast Forum caution potential users of this predictive information that they can expect only modest skill.

 

ENSO Alert System Status: La Nina Advisory

 

Outlook: La Nina conditions are present and favored to persist through December 2025 - February 2026, with a transition to ENSO-neutral likely in January-March 2026 (55% chance).

 

Discussion:

 

La Nina conditions emerged in September 2025, as indicated by the expansion of below-average sea surface temperatures (SSTs) across the central and eastern equatorial Pacific Ocean (Fig. T18). The monthly Nino-3.4 index value was -0.4C, with other regions remaining at or between -0.2C and -0.4C (Table T2). Negative subsurface temperature anomalies persisted (averaged from 180-100W), with below-average temperatures prevailing from the surface to 200m depth in the eastern half of the equatorial Pacific (Fig. T17). Over the western and east-central equatorial Pacific, low-level wind anomalies were easterly and upper-level wind anomalies were westerly (Figs. T20 & T21). Convection continued to be enhanced over Indonesia and was suppressed near the Date Line (Fig. T25). The equatorial Southern Oscillation index was positive (Fig. T2). Collectively, the coupled ocean-atmosphere system reflected La Nina conditions.

The IRI multi-model predictions favor La Nina through the Northern Hemisphere winter 2025-26 (Figs. F1-F12). The North American Multi-Model Ensemble is also in agreement, and based on recently observed anomalies, the team favors La Nina to continue through winter. At this time, La Nina is expected to remain weak (3-month average Nino-3.4 index value at or between -0.5C and -0.9C). A weak La Nina would be less likely to result in conventional winter impacts, though predictable signals could still influence the forecast guidance (e.g., CPC's seasonal outlooks). In summary, La Nina conditions are present and favored to persist through December 2025 - February 2026, with a transition to ENSO-neutral likely in January-March 2026 (55% chance).

Weekly updates of oceanic and atmospheric conditions are available on the Climate Prediction Center homepage (El Nino/La Nina Current Conditions and Expert Discussions).