Forecast Forum - September  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.  Niño 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 likely that slightly warmer-than-average conditions will persist through the Northern Hemisphere winter of 2003-04.

Discussion

Oceanic conditions in the tropical Pacific were slightly warmer-than-average (but still ENSO-neutral) during September 2003. Equatorial SST anomalies greater than +0.5EC (~1̊F) persisted in the region west of the date line during September (Figs. T9, T18), and developed over most of the region between the date line and 120EW during the last half of the month. Observed SST anomalies in the NiZo 3, 3.4 and 4 regions have been positive since July 2003 (Table T2). Positive equatorial upper-ocean temperature departures persisted in the central and east-central equatorial Pacific (Figs. T15, T17). Overall the basin-wide upper ocean heat content was warmer-than-average during the month (Fig. T17).

Generally, atmospheric conditions in the tropical Pacific have been near average in recent months (Table T1), with no significant trends that would support large-scale anomalous warming or cooling of SSTs in that region. Thus, slightly warmer-than-average conditions are likely to persist through the next several months.

A majority of the statistical and coupled model forecasts indicate near-average (ENSO-neutral) conditions in the tropical Pacific (NiZo 3.4 SST anomalies between -0.5EC and +0.5EC) through the NH winter 2003-2004 (Figs. F1, F2, F3, F4a, F4b, F5, F6, F7, F8, F9, F10, F11, F12, F13).  However, over the past few months there has been a trend in the suite of forecasts towards somewhat warmer conditions, consistent with observations. Thus, it is likely that slightly warmer-than-average conditions will persist through the Northern Hemisphere winter of 2003-04.

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: http://www.cpc.ncep.noaa.gov.