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 Niña Watch

 

Outlook: La Niña is favored to emerge in September-November (71% chance) and is expected to persist through January-March 2025.

 

Discussion:

 

ENSO-neutral continued during August 2024, with near-average sea surface temperatures (SSTs) observed across most of the equatorial Pacific Ocean (Fig. T18). The monthly Niño indices did not change substantially, with the latest index values varying between +0.5C (Nino-4) and -0.3C (Nino-1+2; Table T2). Below-average subsurface temperatures were also similar to those in early August. Negative temperature anomalies continued to dominate across most of the subsurface equatorial Pacific Ocean (Fig. T17). Low-level wind anomalies were easterly over most of the equatorial Pacific, and upper-level wind anomalies were easterly over the east-central Pacific (Figs. T20 & T21). Convection was slightly enhanced over parts of Indonesia and was near average near the Date Line (Fig. T25). Both the Southern Oscillation index and the equatorial Southern Oscillation indices were positive (Figs. T1 & T2). 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). This month, the team relies more on the latest North American Multi-Model Ensemble (NMME) guidance, which predicts La Nina to emerge in the next couple of months and continue through the Northern Hemisphere winter. The continuation of negative subsurface temperatures and enhanced low-level easterly wind anomalies supports the formation of a weak 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 (71% 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 Niño/La Niña Current Conditions and Expert Discussions).