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 Watch

 

Outlook:

 

El Niño conditions are likely to develop during September 2012.

 

Discussion:  

 

ENSO-neutral conditions continued during August 2012 despite above-average sea surface temperatures (SST) across the eastern Pacific Ocean (Fig. T18).  Reflecting this warmth, most of the monthly Niño index values remained near +0.5°C (Table T2).  The oceanic heat content (average temperature in the upper 300m of the ocean) anomalies also remained elevated during the month, consistent with a large region of above-average temperatures at depth across the equatorial Pacific (Fig. T17).  Possible signs of El Niño development in the atmosphere included upper-level easterly wind anomalies and a slightly negative Southern Oscillation Index (Table T1). Despite these indicators, key aspects of the tropical atmosphere did not support the development of El Niño conditions during the month.  In particular, low-level trade winds were near average along the equator, and the pattern of tropical convection from Indonesia to the central equatorial Pacific was inconsistent with El Niño with the typical regions of both enhanced and suppressed convection shifted too far west (Figs.T20 and T25). Because of the lack of clear atmospheric anomaly patterns, ENSO-neutral conditions persisted during August. However, there are ongoing signs of a possibly imminent transition towards El Niño in the atmosphere as well as the ocean. 

Most of the dynamical models, along with roughly one-half of the statistical models, now predict the onset of El Niño beginning in August-October 2012, persisting through the remainder of the year (Figs. F1-F13). The consensus of dynamical models indicates a borderline moderate strength event (Niño 3.4 index near +1.0°C), while the statistical model consensus indicates a borderline weak El Niño (+0.4° to +0.5°C). Supported by the model forecasts and the continued warmth across the Pacific Ocean, the official forecast calls for the development of most likely a weak El Niño during September 2012, persisting through December-February 2012-13.

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