Forecast Forum - July 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.  Ni�o 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 next 3-6 months.

Discussion

Sea surface temperature  (SST) anomalies decreased throughout the eastern equatorial Pacific during July (Figs. T9, T18). By the end of the month, equatorial SSTs were near average in most areas between 180�W and the South American coast, while positive anomalies persisted between Indonesia and 180�W (Fig. T18). The decrease in SST anomalies in the eastern equatorial Pacific during July was reflected by a decrease in the SST departures in the Ni�o 3, Ni�o 3.4, and Ni�o 4 regions (Table T2, Fig. T5).  By the end of July the patterns of tropical convection (Fig. T25), low-level winds (Fig. T20), upper-level winds (Fig. T21), SST (Fig. T18) and subsurface ocean temperatures (Fig. T17) were near average, indicating ENSO-neutral conditions.

           The value of the Oceanic Ni�o Index (ONI; 3-month running mean average of SST anomalies in the Ni�o 3.4 region � computed using the Extended Reconstructed SST version-2 data set) for May-July 2005 is +0.3�C, which indicates ENSO neutral conditions.  The large range (weak La Ni�a to weak El Ni�o) in the statistical and coupled model forecasts (Figs. F1, F2, F3, F4a, F4b, F5, F6, F7, F8, F9, F10, F11, F12 and F13) indicates considerable uncertainty. However, current conditions and recent trends support the continuation of ENSO-neutral conditions for the next 3-6 months. 

           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/