Forecast Forum - January 2007

          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

            A transition from weak El Niño conditions to ENSO-neutral conditions is expected by March-May 2007.

Discussion     

SST anomalies decreased across the entire equatorial Pacific during January (Fig. T9, Table T2). However, positive anomalies between +0.5ºC and 1ºC remain in most of the equatorial Pacific between 160ºE and the South American coast (Fig. T18).  The latest SST departures in the Niño regions are around +0.5ºC (Fig. T5). The equatorial upper-ocean heat content peaked in late November and has been decreasing rapidly since that time.  The evolution of the anomalous depth of the 20ºC isotherm (or thermocline) has been consistent with this, with the latest values being negative across much of the equatorial Pacific (Fig. T15).  These trends in surface and subsurface ocean temperatures indicate that the warm episode (El Niño) is weakening.

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 November 2006 – January 2007 is +1.1°C, which indicates weak El Niño conditions.  Most of the statistical and coupled models, including the NCEP Climate Forecast System (CFS), indicate that SST anomalies will continue to decrease and that ENSO-neutral conditions will be present during March-May 2007 (Figs. F1, F2, F3, F4a, F4b, F5, F6, F7, F8, F9, F10, F11, F12 and F13).   The large spread in the most recent set of forecasts indicates that there is considerable uncertainty in this outlook for periods after May 2007.

            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/