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., 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
Based on the recent evolution of the observed oceanic surface and subsurface conditions
and the SST predictions, it is likely that further development towards El Niņo will
continue, with weak-to-moderate El Niņo conditions through early 2003.
Further evolution toward a Pacific basin-wide warm episode (El Niņo) was observed
during May 2002, as sea surface temperature (SST) anomalies increased throughout the
equatorial Pacific between 170°E and 95°W (Figs. T9, T18). By the end of May warmer-than-normal SSTs were observed
throughout the western and central equatorial Pacific, with departures from average
greater than +1°C in the region from 165°E to 135°W and also locally between 130°W and
the South American coast. This warming represents a significant transition from the
localized warmth (central equatorial Pacific and South American coast), observed during
recent months (Fig. T9), toward a more extensive basin-wide
warming typical of El Niņo/Southern Oscillation (ENSO) events.
The warming during May resulted from a significant weakening of the equatorial easterly
winds throughout the Pacific related to the Madden-Julian Oscillation (MJO) (Fig. T13). The MJO is an important source of variability that
can contribute to the evolution toward El Niņo through related fluctuations in low-level
winds and precipitation over the western and central equatorial Pacific. An
eastward-propagating oceanic Kelvin wave, initiated by strong MJO activity in late 2001 (Figs.
T11, T12), resulted in the rapid
warming that was observed along the coasts of Ecuador and northern Peru in early February
(Fig. T9). Subsequently, MJO activity was relatively weak
during early 2002, with no additional significant Kelvin wave activity. However, in late
April 2002 the MJO intensified (Figs. T11, T12) and during the last half of May the low-level equatorial
easterly winds substantially weakened throughout the Pacific (Fig.
T13), accompanied by an increase in equatorial SST anomalies (Fig.
T9). NOAA TAO buoy data indicate that the oceanic thermocline has deepened east of
the date line (180°W) since mid-May, consistent with the basin-wide weakening of the
low-level equatorial easterly winds. This deepening is an indication of renewed Kelvin
wave activity. Given the recent strength of the MJO and its period of about 40 days, it is
likely that significant month-to-month fluctuations will continue to occur in many
atmospheric indices used to monitor the ENSO cycle. In spite of this variability, the
overall trends in SSTs and some atmospheric indices (Southern Oscillation Index, 850-hPa
zonal wind) in recent months indicate that further development towards El Niņo will
continue (Tables T1 and T2).
This assessment agrees well with the latest statistical and coupled model predictions (Figs.
F1, F2, F3,
F4a, F4b, F5, F6, F7,
F8, F9) which indicate
weak-to-moderate El Niņo conditions through early 2003. Based on the recent evolution of
the observed oceanic conditions and the SST predictions, it appears most likely that
warming will continue over the next several months, and that weak-to-moderate El Niņo
conditions will continue into early 2003. It is important to add that a weak or moderate
El Niņo would feature much weaker global impacts than were experienced during the very
strong 1997-98 El Niņo.
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).