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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.
Predictions from the ENSO-CLIPER statistical model (Knaff, J. A. and C. W. Landsea
1997, Wea. Forecasting, 12, 633-652) are shown in Fig. F10.
The CPC and the contributors to the Forecast
Forum caution potential users of this predictive information that they can expect only
modest skill.
Outlook
Warm episode conditions are likely to develop in the tropical Pacific during the next
3-6 months.
Discussion
While several oceanic indices continued to reflect ENSO-neutral conditions during
December (Table T2), trends in the oceanic and atmospheric
conditions during the past several months are consistent with an evolution towards a warm
episode in the tropical Pacific. Since June 2001 sea surface temperatures (SSTs)
have become anomalously warm in the central equatorial Pacific (Fig.
T9), with anomalies near +1°C at the date line by the end of December. During
the same period subsurface temperature anomalies remained positive in the central and
western equatorial Pacific (Fig. T15), indicating a deeper
than normal oceanic thermocline in that region. A substantial increase in subsurface
temperature anomalies was observed in the central and west-central equatorial Pacific
during December (Fig T17).
In recent months, many tropical Pacific atmospheric and oceanic variables have been
strongly modulated by tropical intraseasonal (30-60 day) fluctuations associated with the
Madden Julian Oscillation (MJO). Low-level wind fluctuations over the central and western
tropical Pacific have been consistent with this activity (Fig. T13).
December featured significant low-level westerly anomalies over the western equatorial
Pacific during the first half of the month and over the west-central equatorial Pacific
during the second half of the month (Fig. T13). This
activity generated a strong eastward propagating oceanic Kelvin wave that contributed to
the deepening of the oceanic thermocline in the vicinity of the date line. The magnitude
of this Kelvin wave suggests that an increase in SST’s is likely in the eastern
tropical Pacific in the next month or two. The pattern of anomalous tropical convection
during December was also consistent with the MJO activity (Figs. T11,
T25), with above-normal precipitation extending from the
western tropical Pacific to the date line and along the South Pacific Convergence Zone (Figs.
T25, E3).
The latest statistical and coupled model predictions (Figs. F1, F2, F3,
F4, F7, F8, F9, F10) range from
near-normal to moderate warm episode conditions over the next three to six months.
However, all of these prediction techniques have difficulty in making skillful forecasts
during ENSO transitions. Considering the SST predictions, the time of year, and the
observed oceanic and atmospheric circulation patterns, it seems most likely that warm
episode conditions will develop in the tropical Pacific over the next 3-6 months.
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).
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www.nws.noaa.gov
