Forecast Forum - June  2003

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.  Ni�o 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.

Outlook

Based on current conditions and recent observed trends, it is most likely that near neutral conditions will occur in the tropical Pacific during the last half of 2003.

Discussion

Cooler-than-average surface (Fig. T18) and subsurface (Fig. T17) water temperatures were observed in the east-central and eastern equatorial Pacific during June 2003. However, negative sea-surface temperature anomalies weakened across the central and eastern equatorial Pacific during the month (Fig. T9), consistent with an upward trend in SST anomalies in all of the NiZo regions (Fig. T5, Table T2). Since late May positive equatorial upper-ocean temperature departures have increased in magnitude in the western Pacific and spread eastward into the central and eastern Pacific (Fig. T15). This evolving subsurface pattern is associated with an eastward propagating oceanic Kelvin wave, resulting from a period of weaker-than-average low-level easterlies in the central equatorial Pacific that occurred during late May. These recent trends in surface and subsurface ocean temperature departures do not support the development of La NiZa conditions during the next few months.

The latest statistical and coupled model forecasts indicate considerable uncertainty for the next several months (Figs. F1, F2, F3, F4a, F4b, F5, F6, F7, F8, F9, F10, F11, F12, F13).  However, the majority of the forecasts indicate near neutral conditions (NiZo 3.4 SST anomalies between -0.5EC and +0.5EC) during the last half of 2003. This is consistent with current conditions and recent observed trends.