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HOME > Expert Assessments > Climate Diagnostics Bulletin > Forecast Forum
Forecast Forum - September 2004

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.


Warm-episode (El Niņo) conditions are expected to continue into early 2005.


Positive sea surface temperature (SST) anomalies greater than +0.5°C persisted in the central and western equatorial Pacific (Niņo 4 and Niņo 3.4 regions), and expanded eastward into the eastern equatorial Pacific (Niņo 3 region) during September 2004 (Table T2, Fig. T18).  The increase and eastward expansion of the area of anomalous warmth in the central equatorial Pacific during July-September (Fig. T9) indicates the early stages of a warm (El Niņo) episode.  Through  the end of September conditions were not yet indicative of a basin-wide El Niņo, particularly due to the presence of below-average SSTs in the far eastern equatorial Pacific between 95°W and the South American coast (Fig. T18).

Through most of 2004 MJO activity has resulted in week-to-week and month-to-month variability in many atmospheric and oceanic indices.  In the past few months the warmth in the central equatorial Pacific has supported eastward shifts of enhanced convection associated with the convectively active phase of the Madden-Julian Oscillation (MJO) across the western equatorial Pacific (Figs. T11 and T12).  This activity has been associated with periods of weaker-than-average easterlies (Fig. T13), that initiated eastward-propagating oceanic Kelvin waves, which contributed to a deeper-than-average oceanic thermocline (Figs. T15 and T16) and an increase in the surface and subsurface temperature anomalies in the central and eastern equatorial Pacific (Fig. T17). 

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.   Based on the recent evolution of oceanic and atmospheric conditions and on a majority of the statistical and coupled model forecasts (Figs. F1, F2, F3, F4a, , F4b, F5, F6, F7, F8, F9, F10, F11, F12, F13), 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.

Expected global impacts include drier-than-average conditions over Indonesia (through  early 2005), northern and northeastern Australia (November 2004-February 2005), and southeastern Africa (November 2004-March 2005).  If the warming in the tropical Pacific should strengthen and spread eastward to the South American coast, then wetter-than-average conditions can be expected in coastal sections of Ecuador and northern Peru during the first few months of 2005, and drier-than-average conditions can be expected to develop in the eastern Amazon late this year and spread to Northeast Brazil during February-April 2005.

El Niņo wintertime impacts over the United States vary considerably depending on the character (distribution and intensity) of the warming in the tropical Pacific. Composite impacts for selected ranges of the ONI for El Niņo episodes since 1950 show that the areal extent of warmer-than-average (wetter-than-average) conditions increases across the northern (southern) United States , as the strength of El Niņo increases. The current warming in the tropical Pacific is expected to continue through the upcoming winter, with models indicating an ONI in the range of +0.5ēC to +1.4ēC (Figs. F1, F2, F3, F4a, , F4b, F5, F6, F7, F8, F9, F10, F11, F12, F13) Thus, expected impacts during Northern Hemisphere winter include warmer-than-average conditions  in the West and in the northern Plains, and cooler- and wetter-than-average conditions for portions of the South and Southeast.

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:


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