Forecast Forum - February 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

            A transition from weak warm-episode (El Niño) conditions to ENSO-neutral conditions is expected during the next three months.

Discussion

Sea surface temperature  (SST) anomalies decreased in all of the Niño regions during February 2005 (Table T2). However, positive sea surface temperature (SST) anomalies greater than +1°C (~1.8°F) persisted in portions of the central and western equatorial Pacific (Fig. T18).  The pattern of anomalous warmth in the equatorial Pacific in recent months (Fig. T9) and the most recent  five-month running mean value of the Southern Oscillation Index (-0.5) (Fig. T1) indicate that a weak warm (mid-Pacific El Niño) episode is in progress. However, the recent decrease in SST anomalies throughout the equatorial Pacific suggests that a return to ENSO-neutral conditions is taking place.

In spite of the recent trend in SST anomalies, drier-than-average conditions prevailed over Indonesia and northern Australia during February, while enhanced convection and precipitation persisted over the anomalously warm waters of the central equatorial Pacific (Figs. T11 and T25).  This enhanced convection has been accompanied by strong low-level westerly wind anomalies (Fig. T20) that initiated an eastward-propagating oceanic Kelvin wave.  This wave appears to be stronger than those that have occurred in recent months in association with MJO activity (Fig. T12). At this time there is uncertainty concerning the possible influence of this latest Kelvin wave on the surface and subsurface conditions in the eastern equatorial Pacific.

Based on the recent evolution of oceanic and atmospheric conditions and on 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), it seems most likely that weak warm episode (El Niño) conditions will continue to weaken during the next three months and that ENSO-neutral conditions will prevail during the northern summer.Some lingering effects of the weak warm episode, such as drier-than-average conditions over portions of Indonesia , may continue to be experienced for the next month or two.

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/