| 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 February, 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 continue to dominate the equatorial Pacific east
of the date line (Figs. T16 and T17).
The cooler-than-normal surface waters contributed to a vigorous Walker circulation across
the equatorial Pacific (Fig. T29), characterized by
enhanced low-level easterlies (Fig. T20), enhanced
upper-level westerlies (Fig. T21), suppressed convection
in the central equatorial Pacific and enhanced convection over Indonesia (Figs. T25 and E4). These patterns of anomalous
convection and low-level winds have been highly persistent during the last year,
consistent with ongoing cold episode conditions.
Since December 1999 there has been a slow eastward expansion of the positive subsurface
anomalies into the central Pacific consistent with a slow evolution of the subsurface
thermal structure toward a pre-warm episode state. Historically, this "build-up"
phase of the ENSO cycle has lasted between one and two years before the subsequent
development of warm episode conditions.
The latest NCEP coupled model and statistical model forecasts and other available
forecasts exhibit considerable spread in the evolution of the SSTs over the next 3-9
months. The NCEP coupled model forecast (Figs. F3 and F4) indicates that cold episode conditions will weaken during the
next 3 months, followed by a return to near-normal conditions during June-November. The
NCEP statistical model forecast (Figs. F1 and F2) shows a rapid transition to warm episode conditions over the
next 9 months, while other available coupled model and statistical model predictions (Figs.
F9, F10, F11)
indicate the continuation of cold episode conditions through the end of 2000. The lack of
any rapid evolution in the subsurface thermal structure and the persistence of low-level
easterly anomalies over the central and western equatorial Pacific continues to support a
slower decay in the cold episode conditions than is shown by either the NCEP coupled model
or the NCEP statistical model. Thus, we conclude that cold episode conditions will
gradually weaken over the next 6 months and that near-normal or slightly
cooler-than-normal conditions are likely to be present by the end of the year.
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). |
www.nws.noaa.gov
