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.  Niño 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 Watch

 

Outlook: La Nina is favored to emerge in September-November (60% chance) and is expected to persist through January-March 2025.

 

Discussion:

 

During September 2024, ENSO-neutral continued with near-average sea surface temperatures (SSTs) observed across most of the central and eastern equatorial Pacific Ocean (Fig. T18). The latest monthly Nino indices ranged from +0.3°C (Nino-4) to -0.7°C (Nino-1+2; Table T2). Below-average subsurface temperatures persisted across the east-central and eastern equatorial Pacific Ocean (Fig. T17). Low-level wind anomalies were easterly over the east-central equatorial Pacific, and upper-level wind anomalies were westerly over the eastern Pacific (Figs. T20 & T21). Convection was near average over Indonesia and was slightly suppressed over the Date Line (Fig. T25). Collectively, the coupled ocean-atmosphere system reflected ENSO-neutral.

The IRI plume predicts a weak and a short duration La Nina, as indicated by the Nino-3.4 index values less than -0.5C (Figs. F1-F12). The latest North American Multi-Model Ensemble (NMME) forecasts were warmer this month, but still predict a weak La Nina. As a result of the warmer predictions and the recent weakening of equatorial trade winds, the team still favors a weak event, but has lowered the chances of La Nina. A weaker La Nina implies that it 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 is favored to emerge in September-November (60% chance) and is expected to persist through January-March 2025.

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