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 (CFS03) 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 using linear inverse modeling (Penland and Magorian 1993: J. Climate, 6, 1067‑1076) are shown in Figs. F9 and F10. Predictions from the Scripps / Max Planck Institute (MPI) hybrid coupled model (Barnett et al. 1993: J. Climate, 6, 1545‑1566) are shown in Fig. F11.  Predictions from the ENSO‑CLIPER statistical model (Knaff and Landsea 1997, Wea. Forecasting, 12, 633‑652) are shown in Fig. F12.  Niño 3.4 predictions are summarized in Fig. F13, 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:  El Niño Advisory

 

Outlook:

 

There is an approximately 90% chance that El Niño will continue through Northern Hemisphere summer 2015, and a greater than 80% chance it will last through 2015.

 

Discussion:  

 

            By the end of April 2015, weak to moderate El Niño conditions were reflected by above-average sea surface temperatures (SST) across the equatorial Pacific (Fig. T18), and by the corroborating tropical atmospheric response. The latest monthly Niño indices were +1.2°C in the Niño-4 region, +0.8°C in the Niño-3.4 region, and +0.7°C and +1.4°C in the Niño-3 and Niño-1+2 regions, respectively (Table T2). Subsurface temperature anomalies remained substantially above average, partly in response to a downwelling oceanic Kelvin wave, which resulted in strong positive subsurface anomalies across the central and eastern Pacific (Fig. T17). This anomalous warmth has subsequently persisted in association with El Niño-related ocean-atmosphere coupling. This coupling includes enhanced convection over the central equatorial Pacific (Fig.T25), along with persistent low-level westerly wind anomalies over the western and central equatorial Pacific and persistent upper-level easterly wind anomalies over the central Pacific (Figs.T20, T21). Also, the equatorial Southern Oscillation Index (EQSOI) remained negative during the month (Fig. T2). Collectively, these features reflect weak to moderate strength El Niño conditions.

Nearly all models predict El Niño (3-month values of the Niño-3.4 index 0.5°C or greater) to continue throughout 2015, and many are also predicting SST anomalies to increase during the next several months (Figs. F1-F13). These forecasts are supported by the continuation of positive subsurface temperature anomalies, enhanced convection near the Date Line, and the persistence of low-level westerly wind anomalies. Given these factors, it is likely that SST anomalies will continue to increase in the coming months. However, model forecast skill tends to be lower during the Northern Hemisphere spring, which somewhat limits confidence in these forecasts. Therefore, there remains considerable uncertainty about how strong this event may become. In summary, there is an approximately 90% chance that El Niño will continue through Northern Hemisphere summer 2015, and a greater than 80% chance it will last through 2015.

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