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HOME > Expert Assessments > Climate Diagnostics Bulletin > Forecast Forum
Forecast Forum - April 2005

          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 Forecast System Model (CFS03) are presented in Figs. F3 and F4a, F4b.  Predictions from the Markov model (Xue, et al. 2000: J. Climate, 13, 849‑871) are shown in Figs. F5 and F6.   Predictions from the latest version of the LDEO model (Chen 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 and Landsea 1997, Wea. Forecasting, 12, 633‑652) are shown in Fig. F12.  Niño 3.4 predictions are summarized in Fig. F13, 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.



            ENSO-neutral conditions are expected to prevail during the northern summer (June-August).




Surface and subsurface water temperatures increased in the eastern equatorial Pacific during April (Table T2, Fig. T5), associated with the arrival of the downwelling phase of a strong oceanic Kelvin wave (Fig. T17).  By the end of April positive equatorial SST anomalies greater than +0.5°C (~0.9°F) were observed in most areas from Indonesia eastward to the South American coast (Fig. T18). The increase in SST anomalies in the eastern equatorial Pacific during April was reflected by an increase in the SST anomalies in the Niño 3 and Niño 1+2 regions (Table T2) and by an increase in the upper-ocean heat content in the eastern half of the equatorial Pacific (Fig. T15).  Subsurface cooling and a decrease in upper-ocean heat content have been evident in the central equatorial Pacific, associated with the upwelling phase of the Kelvin wave (Fig. T17).   This cooling is expected to propagate eastward, reaching the eastern equatorial Pacific during May. Thus, the effects of the warming along the west coast of South America should be brief.

Cloudiness, precipitation and low-level winds displayed considerable week-to-week variability during the month, associated with strong MJO activity (Figs. T11, T12 and T13). For the month as a whole, enhanced precipitation (negative OLR anomalies) prevailed over the western Pacific (Fig. T25), accompanied by stronger-than-average low-level easterly winds over the central equatorial Pacific and anomalous low-level westerly winds over the extreme western equatorial Pacific (Fig. T20). Continued strong week-to-week variability in the patterns of tropical atmospheric circulation and precipitation is likely during May.

          The value of the Oceanic Niño Index (ONI; 3-month running mean average of SST anomalies in the Niño 3.4 region – computed using the Extended Reconstructed SST version-2 data set) for February-April 2005 is +0.3°C, which does not satisfy the NOAA operational definition of El Niño for the first time since May-July 2004.  Consistent with this, a majority of the statistical and coupled model forecasts (Figs. F1, F2, F3, F4a, F4b, F5, F6, F7, F8, F9, F10, F11, F12 and F13) indicate that ENSO-neutral conditions will prevail during the northern summer (June-August). The spread in the forecasts indicates increasing uncertainty during the last half of 2005.

     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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