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HOME > Expert Assessments > Climate Diagnostics Bulletin

Forecast Forum - January 2000

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 Cane and Zebiak model (Cane et al. 1986, Nature, 321, 827-832; Zebiak and Cane 1987, Mon. Wea. Rev., 115, 2262-2278) are shown in Figs. F5 and F6. Predictions from the modified Cane and Zebiak model (Chen et al. 1998, Geophys. Res. Let., 103, 2387-2840), referred to in the figures as LDEO3, 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.

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

Discussion and Outlook

Strong cold episode conditions continued in the tropical Pacific during January, as sea surface temperatures (SSTs) remained well below normal across the central and east-central equatorial Pacific (Fig. T18 and Table T2). Negative subsurface temperature anomalies and a shallower-than-normal oceanic thermocline continued to dominate the equatorial Pacific east of the date line (Fig. T16). Tropical convection during January (as inferred from Outgoing Longwave Radiation (OLR) measured by NOAA’s polar-orbiting satellites) was suppressed over the western and central equatorial Pacific and enhanced over Indonesia (Fig. T25). Accompanying these conditions, the mean low-level equatorial easterly winds were stronger-than-normal over the western and central tropical Pacific and near normal over the eastern Pacific (Fig. T20). These patterns of anomalous convection and low-level winds have been highly persistent during the last year, consistent with ongoing cold episode conditions.

Over the past several months the pattern of subsurface temperature anomalies has been very persistent, with positive anomalies in the western equatorial Pacific and negative anomalies in the eastern equatorial Pacific (Fig. T17). A notable feature of the current cold episode is the lack of evolution of the subsurface thermal structure from a pattern that is typical of the mature phase of cold episodes towards a pre-warm episode state. Thus, it is likely that cold episode conditions will continue for at least the next several months. This assessment is supported by the most recent NCEP coupled model forecast (Figs. F3 and F4) and by other available coupled model and statistical model predictions that indicate cold episode conditions persisting through the spring of 2000, followed by a return toward normal SSTs during the last half of the year.

Based on current conditions in the tropical Pacific, on the NCEP SST predictions, and on results from historical studies on the effects of cold episodes, we expect wetter-than-normal conditions to continue through March over Indonesia, northern Australia, and southern Africa. Wetter-than-normal conditions should continue over northeastern South America through May. Over the United States, drier- and warmer-than-normal conditions are expected along the southern tier of states from southern California eastward to the Carolinas. Cooler-than-normal conditions are also likely over southern Alaska, western and central Canada and in the upper Midwest.

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

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