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HOME > Expert Assessments > Climate Diagnostics Bulletin
Forecast Forum - December 2001

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 ocean/atmosphere model (Ji et al. 1998, Mon. Wea. Rev, 126, 1022-1034) are presented in Figs. F3 and F4. Predictions from the latest version of the LDEO model (Chen, D., M. A. Cane, S. E. Zebiak, Rafael Canizares and A. Kaplan, 2000, Geophys. Res. Let., accepted) are shown in Figs. F5 and F6. Predictions using linear inverse modeling (Penland and Magorian 1993, J. Climate, 6, 1067-1076) are shown in Figs. F7 and F8. Predictions from the Scripps / Max Planck Institute (MPI) hybrid coupled model (Barnett et al. 1993, J. Climate, 6, 1545-1566) are shown in Fig. F9.   Predictions from the ENSO-CLIPER statistical model (Knaff, J. A. and C. W. Landsea 1997, Wea. Forecasting, 12, 633-652) are shown in Fig. F10.

The CPC and the contributors to the Forecast Forum caution potential users of this predictive information that they can expect only modest skill.


Warm episode conditions are likely to develop in the tropical Pacific during the next 3-6 months.


While several oceanic indices continued to reflect ENSO-neutral conditions during December (Table T2), trends in the oceanic and atmospheric conditions during the past several months are consistent with an evolution towards a warm episode in the tropical Pacific. Since June 2001 sea surface temperatures (SSTs) have become anomalously warm in the central equatorial Pacific (Fig. T9), with anomalies near +1°C at the date line by the end of December. During the same period subsurface temperature anomalies remained positive in the central and western equatorial Pacific (Fig. T15), indicating a deeper than normal oceanic thermocline in that region. A substantial increase in subsurface temperature anomalies was observed in the central and west-central equatorial Pacific during December (Fig T17).

In recent months, many tropical Pacific atmospheric and oceanic variables have been strongly modulated by tropical intraseasonal (30-60 day) fluctuations associated with the Madden Julian Oscillation (MJO). Low-level wind fluctuations over the central and western tropical Pacific have been consistent with this activity (Fig. T13). December featured significant low-level westerly anomalies over the western equatorial Pacific during the first half of the month and over the west-central equatorial Pacific during the second half of the month (Fig. T13). This activity generated a strong eastward propagating oceanic Kelvin wave that contributed to the deepening of the oceanic thermocline in the vicinity of the date line. The magnitude of this Kelvin wave suggests that an increase in SST’s is likely in the eastern tropical Pacific in the next month or two. The pattern of anomalous tropical convection during December was also consistent with the MJO activity (Figs. T11, T25), with above-normal precipitation extending from the western tropical Pacific to the date line and along the South Pacific Convergence Zone (Figs. T25, E3).

The latest statistical and coupled model predictions (Figs. F1, F2, F3, F4, F7, F8, F9, F10) range from near-normal to moderate warm episode conditions over the next three to six months. However, all of these prediction techniques have difficulty in making skillful forecasts during ENSO transitions. Considering the SST predictions, the time of year, and the observed oceanic and atmospheric circulation patterns, it seems most likely that warm episode conditions will develop in the tropical Pacific over the next 3-6 months.

Weekly updates of SST, 850-hPa wind, OLR, and the equatorial subsurface temperature structure are available on the Climate Prediction Center homepage at: (Weekly Update).

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