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 expected in the tropical Pacific through early 2001.
Cold episode (La Niņa) conditions continued to weaken during July, with
near-normal oceanic and atmospheric conditions by the end of the month. Negative SST
anomalies continued to weaken across the central tropical Pacific during July (Figs. T9, T18). The oceanic thermocline
remained deeper-than-normal in the equatorial west-central and western Pacific (Fig. T15), with temperatures averaging up to 4°C above
normal at thermocline depth (Fig. T17). The negative
temperature anomalies that have characterized the subsurface thermal structure in the
eastern Pacific since late 1998 weakened during July (Figs. T15,
T17). The recent evolution of the oceanic thermocline and
subsurface temperature anomalies is similar to that observed during 1999, with the major
difference being an increase in the magnitude of the positive subsurface temperature
anomalies in the western Pacific and a decrease in the magnitude of the negative anomalies
in the eastern Pacific.
The pattern of tropical convection [as inferred from anomalous outgoing longwave
radiation (OLR)] remained consistent with weak cold episode conditions during the month,
with suppressed convection over the western and central equatorial Pacific (Fig. T25). However, consistent with the decrease in magnitude
of the negative SST anomalies across the central equatorial Pacific in recent months, the
low-level easterly wind anomalies across the central and western tropical Pacific have
decreased in intensity (Figs. T7, T20).
The most recent NCEP statistical and coupled model forecasts, as well as other
available forecasts, exhibit considerable spread in the evolution of the tropical Pacific
SSTs over the next 3-9 months. The NCEP coupled model forecast (Figs. F3 and F4) and the LDEO forecast (Figs.
F5 and F6) indicate near-normal
conditions into early next year. The NCEP statistical model forecast (Figs. F1 and F2) and other available coupled
model and statistical model predictions (Figs. F7, F8, F9)
indicate the gradual weakening of negative SST anomalies through early 2001.
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