Forecast Forum - February 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 ENSO-neutral to La Niña conditions is possible during the next 2-3 months.

Discussion     

SST anomalies decreased across the equatorial Pacific east of the date line during February 2007 (Table T2) as negative anomalies replaced positive anomalies in the central and east central equatorial Pacific (Fig. T18). By the end of the month positive anomalies greater than +0.5ºC along the equator were restricted to the region between 145ºE and the date line (180º).  The latest weekly SST departures in the Niño regions were around 0.5ºC in the Niño 4 region, near 0ºC in the Niño 3.4 region and slightly negative in the Niño 3 and Niño 1+2 regions. The equatorial upper-ocean heat content (average temperature departures in the upper 300 m of the ocean) decreased rapidly during December 2006-January 2007, as the upper ocean cooled and negative temperature anomalies developed (Fig. T15). The recent cooling has been accompanied by persistent stronger than-average low-level easterly winds over the central equatorial Pacific (Figs. T7 and T20).  Collectively, these oceanic and atmospheric conditions indicate that the warm (El Niño) episode has ended and that conditions are becoming more favorable for La Niña to develop.

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 December 2006 – February 2007 is +0.8°C, which reflects the weak El Niño conditions that prevailed during December 2006 and January 2007.   Most of the statistical and coupled models, including the NCEP Climate Forecast System (CFS), indicate that SST anomalies will continue to decrease during the next 2-3 months (Figs. F1, F2, F3, F4a, F4b, F5, F6, F7, F8, F9, F10, F11, F12 and F13).  Some of the forecast models, especially the CFS, indicate a rapid transition to La Niña conditions during March-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/