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.

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

Outlook

Cold episode (La Ni�a) conditions are expected to continue through the remainder of the NH winter and into the spring of 2001 followed by a return to near-normal conditions during the summer of 2001.

Discussion

Cold episode conditions continued in the tropical Pacific during December, as sea surface temperatures (SSTs) remained well below normal across the central and east-central equatorial Pacific (Fig. T18 and Table T2). Below-normal subsurface temperatures continue to dominate the eastern equatorial Pacific while above normal subsurface temperatures dominate the western Pacific (Fig. T17). Tropical convection during December (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 the Phillippines, portions of Indonesia and northern Australia (Fig. T25). Consistent with these conditions, the mean low-level equatorial easterly winds remained stronger-than-normal over the western and central tropical Pacific and near normal over the eastern Pacific (Fig. T20). The patterns of tropical convection and low-evel winds have been strongly influenced by tropical intraseasonal (Madden-Julian Oscillation) activity (Fig. T11), which has been present since June 2000 (Fig. T12).

As in previous months, a notable feature of the current oceanic conditions is the lack of evolution of the subsurface thermal structure in the tropical Pacific 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 be present through the remainder of the NH winter and into the spring of 2001. This assessment is generally supported by the most recent NCEP statistical and coupled model forecasts (Figs. F1, F2, F3, F4), as well as by other available coupled model and statistical model predictions (Figs. F5, F6, F7, F8) that indicate a gradual weakening of cold episode conditions in the tropical Pacific through the remainder of the NH winter, followed by near-normal SSTs during the spring of 2001. However, over the past several months the forecast tools have weakened cold episode conditions more rapidly than has been observed.

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 average conditions to prevail over Indonesia, northern Australia, and southern Africa during the remainder of the NH winter. Over North America warmer-than-normal average conditions are expected along the southern tier of the United States from southern California eastward to Florida. Cooler-than-normal average conditions are likely over western and central Canada and in the upper Midwest and Great Lakes.

Weekly updates of SST, 850-hPa wind and OLR are available on the Climate Prediction Center homepage at: http://www.cpc.ncep.noaa.gov (Weekly Update).