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HOME > Expert Assessments > Climate Diagnostics Bulletin > Forecast Forum
Forecast Forum - December 2005

          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.



            Weak La Niña conditions are expected to continue during the next 3-6 months.



Equatorial SST anomalies greater than +0.5ºC were restricted to the region between Indonesia and 170ºE during December, while negative anomalies less than –0.5ºC were observed at most locations between the date line and the South American coast (Figs. T9 and T18). The SST departures in the Niño 3, Niño 3.4 and Niño 1+2 regions were negative, while weak positive departures were observed in the Niño 4 region (Table T2 and Fig. T5).   During the last several months surface and subsurface temperature anomalies have decreased in the region between 180ºW and the South American coast (Figs. T9, T15 and T17).  During the same period persistent stronger-than-average low-level equatorial easterly winds were observed over the central Pacific (Figs. T7 and T13).  Since early November there has been a persistent pattern of enhanced  tropical convection near 130ºE (Indonesia) and suppressed convection near the date line (180ºW) (Figs. T8 and T25).  Collectively, the present oceanic and atmospheric anomalies are consistent with the early stages of a La Niña episode in the tropical Pacific. 

           Over the past several months most of the statistical and coupled model forecasts have trended towards cooler conditions in the tropical Pacific through mid-2006.  The spread of the most recent statistical and coupled model forecasts (weak La Niña to weak El Niño) indicates some uncertainty in the outlooks (Figs. F1, F2, F3, F4a, F4b, F5, F6, F7, F8, F9, F10, F11, F12 and F13). However, current conditions (stronger-than-average easterly winds over  the central equatorial Pacific) and recent cooling trends in observed oceanic conditions support the continuation of La Nina conditions in the tropical Pacific during the next 3-6 months. 

Based on current conditions in the tropical Pacific, the most recent SST predictions, and on results from historical studies on the effects of cold episodes, we expect wetter-than-normal (drier-than-normal) conditions to prevail over Indonesia (central equatorial Pacific) during the remainder of the NH winter. That pattern of tropical precipitation favors a northward shift in the position of the jet stream over the eastern North Pacific during winter, which is usually accompanied by drier-than-normal conditions over southern California and Arizona .  However, given the late onset of La Niña there is considerable uncertainty as to whether or not typical La Niña impacts will be experienced in the West during the remainder of NH winter.

           Weekly updates of SST, 850-hPa wind, OLR and features of the equatorial subsurface thermal structure are available on the Climate Prediction Center homepage at:


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