Forecast Forum - May 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.

Outlook

            ENSO-neutral conditions are expected during the northern summer and fall (June-November) 2005.

Discussion

           Sea surface temperature (SST) anomalies decreased in the eastern equatorial Pacific during May (Figs. T9, T18). By the end of the month, negative equatorial SST anomalies were observed in most areas between 120°W and the South American coast (Fig. T18). The decrease in SST anomalies in the eastern equatorial Pacific during May was reflected by a decrease in the SST anomalies in the Niño 3 and Niño 1+2 regions (Table T2, Fig. T5) and by a decrease in the upper-ocean heat content in the eastern half of the equatorial Pacific (Figs. T15 and T17). These features were associated with the upwelling phase of an eastward-propagating Kelvin wave. No additional Kelvin wave activity is expected, since the MJO has weakened during the last few weeks (Figs. T11 and T12) and the overall patterns of tropical convection (Fig. T25), low-level winds (Fig. T20), and upper-level winds (Fig. T21) are near average.

          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 March-May 2005 is +0.4°C, which indicates ENSO neutral conditions.  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) and fall (September-November). 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: http://www.cpc.ncep.noaa.gov/