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HOME > Expert Assessments > Climate Diagnostics Bulletin > Forecast Forum
Forecast Forum - December 2002

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 F4a, F4b.  Predictions from the Markov model (Xue, Y., A. Leetmaa, and M. Ji, 2000: ENSO prediction with Markov model: The impact of sea level. J. Climate, 13, 849-871) are shown in Figs. F5 and F6.   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., 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, J. A. and C. W. Landsea 1997, Wea. Forecasting, 12, 633-652) are shown in Fig. F12.

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


Based on the recent evolution of conditions in the tropical Pacific and on coupled model and statistical model forecasts, basin-wide warm (El Niņo) episode conditions are expected to continue through the northern spring of 2003.


Warm episode (El Niņo) conditions dominated the tropical Pacific during December 2002. Equatorial SST anomalies were greater than +1°C throughout most of the Pacific between the date line and the South American coast, and exceeded +2°C at several locations between 175°W and 100°W (Fig. T18). Positive subsurface temperature departures (Fig. T17) and a deeper-than-average oceanic thermocline (Figs. T15 and T16) prevailed throughout the equatorial Pacific east of 180°W. Negative subsurface temperature departures were observed west of 180°W at a depth of between 100 and 150 m. This dipole pattern is a typical feature observed during the mature phase of El Niņo.

Atmospheric indicators of El Niņo include consistently negative values of the Tahiti-Darwin Southern Oscillation Index (SOI) since March 2002 (Table T1), and weaker-than-average low-level easterly winds since May 2002 throughout the equatorial Pacific (Table T1, Fig. T7). Values of atmospheric and oceanic indices such as the SOI, 850-hPa zonal wind index, and NiZo 3.4 SST index are all considerably less in magnitude than those observed during the 1997-98 El Niņo (Figs T1, T2, T3, T4, and T5). Recent impacts of the current El Niņo include: drier-than-average conditions over Indonesia, eastern Australia, Central America and northeastern South America and wetter-than-average conditions over the central equatorial Pacific, southeastern South America and the southeastern United States (Figs. E3, E4, E5 and T25). Most coupled model and statistical model forecasts indicate that El Niņo conditions will continue through the northern spring of 2003 (Figs. F1, F2, F3, F4, F5, F6, F7, F8, F9, F10, F11, F12). Thereafter the forecasts are more uncertain, during a time of the year when all of the techniques have difficulty in making skillful forecasts. Historically, most of the techniques have demonstrated more skill in forecasting the onset of El Niņo episodes than in forecasting their demise. A critical factor governing the duration of the current warm episode is the rate of evolution of the dipole pattern in the subsurface thermal structure along the equatorial Pacific, which is linked to the persistence and eastward extension of the pattern of deep convection into the eastern Pacific and persistence of low-level westerly zonal wind anomalies. The Climate Prediction Center will continue to monitor these features over the next few months.

Expected global impacts of the warm episode include: 1) drier-than-average over Indonesia and eastern Australia continuing during the next several months, 2) drier-than-average over southeastern Africa during January-March 2003, 3) drier-than-average over Northeast Brazil and northern South America during January-April 2003, and 4) wetter-than-average conditions over coastal sections of Ecuador and northern Peru during February-April 2003. Over the United States and Canada, during the remainder of the northern winter, expected conditions include: 1) drier-than-average in the Ohio Valley states and northern U.S. Rockies, 2) wetter-than-average along much of the southern tier of the U.S., and 3) warmer-than-average in the northern tier states, southern and southeastern Alaska, and western and central Canada.

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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