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 Markov model (Xue,
Y. et al. 2000: ENSO prediction with Markov model: The impact of sea level. J. Climate,
13, 849-871) are shown in Figs. F5 and F6.
Predictions from the latest version of the LDEO model (Chen,
D. et al. 2000, Geophys. Res. Let., 27,
2585-2587) 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. Predictions from the ENSO-CLIPER statistical model
(Knaff, J. A. and C. W. Landsea 1997, Wea. Forecasting, 12, 633-652) are
shown in Fig. F12. Niņo
3.4 predictions are summarized in F13,
which is provided by the Forecasting
and Prediction Research Group of the IRI.
The CPC and the contributors to the Forecast Forum caution potential users of
this predictive information that they can expect only modest skill.
(El Niņo) conditions are expected to
continue through early 2005.
sea surface temperature (SST) anomalies persisted in the central
and western equatorial Pacific during August 2004 (Table T2). Positive
SST anomalies greater than +1°C were found between 170°E and 130°W,
while negative SST anomalies less than -0.5°C were found between 100°W
and the South American coast (Fig. T18).
The recent increase and eastward expansion of the area of
anomalous warmth in the central equatorial Pacific during July-August (Fig.
T9) indicate the early stages of a warm (El Niņo)
the end of August conditions were not yet indicative of a basin-wide El
Niņo, particularly due to the presence of below normal sea-surface
temperatures in the far eastern equatorial Pacific (Fig. T18). In
spite of the anomalous warmth in the central equatorial Pacific during
August, there appears to be little or no reflection of that warmth in
the pattern of deep convection (precipitation) (Figs. T25,
in the pattern of low-level winds (Fig. T20) over the region.
intraseasonal variability (MJO activity) in recent months has resulted
in week-to-week and month-to-month variability in many atmospheric and
oceanic indices (Table T1). Most
recently, a strong oceanic Kelvin wave, initiated by weaker-than-average
easterly winds in June (Fig. T13), propagated eastward resulting
in a substantial deepening of the oceanic thermocline (Figs. T15 and
T16) and an increase in the subsurface temperature anomalies in the
central and east-central equatorial Pacific (Fig. T17).
This Kelvin wave reached the South American coast during late
August, resulting in an increase in SSTs along the coasts of Ecuador and
northern Peru. Another
substantial weakening of the equatorial easterlies occurred during late
August (Fig. T13), which appears to have initiated another
eastward-propagating Kelvin wave in the central equatorial Pacific.
The NOAA operational definition for El Niņo
[Oceanic Niņo Index (ONI), a three-month
running mean of the Niņo 3.4 index, greater than or equal to +0.5°C] was
satisfied for the period June-August 2004 with an ONI value of +0.7°C.
A majority of the statistical and coupled model forecasts
indicate that El Niņo conditions will continue for the next 3-6 months
with the remaining forecasts indicating near neutral conditions in the
tropical Pacific through the end of 2004 (Figs.
F1, F2, F3,
F4a, , F4b, F5,
F6, F7, F8,
F9, F10, F11,
Based on the recent evolution of oceanic and
atmospheric conditions and on the statistical and coupled model
forecasts, it seems most likely that SST anomalies in the Niņo
3.4 region will remain positive, at or above +0.5°C,
through early 2005. At this time it is not clear what, if any, impacts
this event will have on ocean temperatures in the classical El Niņo
region (Niņo 1+2) along the west coast
of South America. CPC will continue to monitor the situation in
the tropical Pacific and will provide more detailed information on
possible regional impacts due to this event in coming months.
Weekly updates of SST, 850-hPa wind, OLR and features of the
equatorial subsurface thermal structure are available on the Climate
Prediction Center homepage at: