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.
Near-normal conditions are likely in the tropical Pacific during Northern Hemisphere
summer, followed by near-normal or slightly warmer-than-normal conditions into early 2002.
The large-scale oceanic and atmospheric circulation patterns were consistent with weak
cold episode conditions in the tropical Pacific during April. Negative SST anomalies
continued to weaken across the central tropical Pacific during the month (Figs. T9, T18). The anomalously warm SSTs that
were present over most of the eastern tropical Pacific during February and March 2001 have
weakened as cross-equatorial flow became established over the region during April. A
similar evolution was observed in each of the last three years (Fig.
T9). The slope of the oceanic thermocline remained greater than normal, with
positive subsurface temperature anomalies in the western and central equatorial Pacific
and negative anomalies in the eastern Pacific (Figs. T16 and T17). Cold episode related atmospheric features included
stronger-than-normal low-level easterly winds over the western tropical Pacific (Fig. T20), above-normal precipitation over Indonesia (Fig. T25), and suppressed rainfall near the date line (Fig. T25). Overall, the patterns of anomalous 850-hPa zonal
wind and convection have shown remarkable similarity over the central equatorial Pacific
during the last three years, with a distinct annual cycle featuring maxima in the
low-level easterly winds (Fig. T7) and maxima in the OLR
anomalies (Fig. T8) during the northern winter seasons.
Over the past two years there has been a gradual eastward expansion of the area of
positive subsurface temperature anomalies into the central Pacific (Fig.
T15). This evolution is consistent with a slow decay of the subsurface thermal
structure that characterizes the mature phase of cold episodes. Thus, it is likely that
cold episode conditions will continue to weaken, with near-normal conditions likely during
the summer of 2001. This assessment is generally supported by the most recent NCEP
statistical (Figs. F1 and F2) and
coupled model forecasts (Figs. F3 and F4),
as well as by other available coupled model and statistical model predictions (Figs. F5, F6, F7, F8, and F9), which indicate near-normal
conditions during Northern Hemisphere summer. Thereafter, the models indicate near-normal
or slightly warmer-than-normal conditions into early 2002.
Weekly updates of SST, 850-hPa wind, OLR, and the equatorial subsurface temperature
structure are available on the Climate Prediction Center homepage at:
http://www.cpc.ncep.noaa.gov (Weekly Update).