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 F4a, F4b.
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., 27,
2585-2587) 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.
Based on the observed oceanic and atmospheric conditions and the SST predictions,
weak-to-moderate warm episode (El Niņo)conditions are expected to continue during the
remainder of 2002 and into early 2003.
Warm episode (El Niņo) conditions prevailed in the tropical Pacific during July 2002.
Sea surface temperature (SST) anomalies remained greater than +1°C throughout the central
equatorial Pacific between 170°E and 130°W (Fig. T18).
For the second consecutive month the Niņo 3, Niņo 3.4 and Niņo 4 indices were all at or
above +0.5°C (Table T2). Atmospheric indicators of a warm
episode (El Niņo) include consistently negative values of the Southern Oscillation Index
(SOI) since March 2002 (Table T1), and weaker-than-average
low-level easterly winds during May-July 2002 throughout the equatorial Pacific (Fig. T7).
The Madden-Julian Oscillation (MJO) continues to be a major source of week-to-week and
month-to-month variability in the atmospheric circulation of the Tropics and subtropics (Figs.
T11, T12, T13).
The MJO contributed to a substantial weakening of the low-level easterly winds throughout
the equatorial Pacific during July (Figs. T13, T20). As a consequence, drier-than-average conditions were
observed over Indonesia and portions of Southeast Asia / India during the month (Figs. T25, E3, E4). In
addition, the weaker-than-average easterly winds contributed to a deepening of the oceanic
thermocline in the central equatorial Pacific (Figs. T15, T16), an increase in subsurface temperature anomalies (Fig. T17) and an increase in SST anomalies in the central
equatorial Pacific (Fig. T9).
The oceanic and atmospheric variables discussed above reflect the presence of
weak-to-moderate El Niņo conditions. This assessment is consistent with most coupled
model and statistical model forecasts (Figs. F1, F2, F3, F4, F5, F6, F7, F8, F9, F10),
which indicate that El Niņo conditions are likely to continue through the end of 2002 and
into early 2003. While SST anomalies in several of the models decrease in the first season
and then remain above average in subsequent seasons (e.g. Figs. F2
and F4), those in other models increase in the first season
(e.g. Figs. F6 and F10). Since
each model has its own initialization, this may be related to month-to-month variations in
initial conditions due to the strong MJO activity noted above. Although there is
considerable uncertainty in the forecasts about the timing and intensity of the peak of
this warm episode, all of the forecasts indicate that it will be much weaker than the
1997-98 El Niņo. It is important to add that the global impacts of this warm episode
should be correspondingly weaker than those observed during the very strong 1997-98 El
Based on the current conditions in the tropical Pacific, on the SST predictions, and on
results from historical studies of the effects of ENSO, we expect drier-than-average
conditions to continue over Indonesia and eastern Australia during the next several
months, and wetter-than-average conditions over southeastern South America during the next
three months. In the United States drier-than-average conditions are expected in the
Pacific Northwest and mid-Atlantic states during the fall and early winter and in the Ohio
Valley states during the winter. Wetter-than-average conditions are expected in the Gulf
Coast states during the winter, and warmer-than-average conditions are expected in the
Northern Great Plains, upper Midwest, and western and central Canada during late fall and
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).