Because the CCA (Barnston 1994) and OCN (Huang et al. 1995) methods are now being used for the official operational long-lead seasonal forecasts issued by the Climate Prediction Center of NCEP, they are not presented in detail in this Experimental Forecast Bulletin. However, a brief summary of these forecasts, as well as that of the NCEP coupled model (Ji et al. 1994), for Jan-Feb-Mar and Apr-May-Jun 1997 is provided. For further information about the official NCEP forecasts, the following U.S. Regional Climate Center (RCC) Offices may be contacted:

Northeastern RCC 607-255-5950

Southeastern RCC 803-737-0800

Southern RCC 504-388-5021

Midwest RCC 217-244-8226

High Plains RCC 402-472-8294

Western RCC 702-677-3106

The forecasts themselves are contained in the Climate Outlook, available on Internet with address: http://nic.fb4.noaa.gov. That same address can also be used to access the web site for this Bulletin, as follows: http://nic.fb4.noaa.gov/products/predictions; then click on "product A-Z list".

U.S. Surface Climate Forecasts for Jan-Feb-Mar '97Temperature: OCN forecasts warmth along eastern seaboard, Texas and the Southwest. CCA predicts warmth from Southeast to Texas, northern tier (Minnesota eastward), and Kahului; cold Aleutians and Washington. The coupled model dynamical forecast calls for warm Pacific Northwest, cold in Florida.

Precipitation: CCA predicts dryness south-central Alaska, wet northern Hawaii. OCN predicts wetness Southwest. The coupled model predicts dry Florida.

U.S. Surface Climate Forecasts for Apr-May-Jun'97Temperature: CCA predicts warmth Southwest, near-normal most of Hawaii. OCN forecasts warmth Southwest, Northwest, and northern Appalachians; cold Southeast. The coupled model predicts warmth in Washington, Florida.

Precipitation: CCA and the coupled model have no usable skills for this period. OCN predicts above median rainfall in Washington and Oregon.

Note: The above forecast descriptions include only regions whose estimated cross-validated correla-tion skill exceeds 0.3. Highest local skills are usually in the neighborhood of 0.6, but this varies with season, lead time and forecast tool.

ENSO-Related SST

CCA (Barnston and Ropelewski 1992, Smith et al. 1995) predicts slightly below normal SST conditions in Nino 3.4 (120-170^oW, 5 ^oN-5 ^oS) for this winter 1996-97, switching to a positive anomaly by spring and strengthening (with low confidence) by summer. Specifically, CCA forecasts the following standardized anomalies and cross-validated correlation skills:

forecast skill

Jan-Feb-Mar 1997 -0.28 0.90

Apr-May-Jun 1997 0.67 0.59

Jul-Aug-Sep 1997 1.34 0.25

Oct-Nov-Dec 1997 1.52 0.29

Jan-Feb-Mar 1998 1.09 0.45

The forecast for Jan-Feb-Mar 1997 is a skill-weighted average of CCA and simple persistence of the anomaly observed in Sep-Oct-Nov, because persistence and CCA skills are similar for that forecast. Longer lead forecasts reflect only CCA. The global field of SST anomaly for December 8-14, 1996 (Fig. 1) shows the currently somewhat below normal SST in parts of the eastern equatorial Pacific, especially east of 120^oW.

Barnston, A.G., 1994: Linear statistical short-term climate predictive skill in the Northern Hemisphere. J. Climate, 5, 1514-1564.

Barnston, A.G. and C.F. Ropelewski, 1992: Prediction of ENSO episodes using canonical correlation analysis. J. Climate, 7, 1316-1345.

Huang, J., H.M. van den Dool and A.G. Barnston, 1996: Long-lead seasonal temperature prediction using optimal climate normals. J. Climate, 9, 809-817.

Ji, M., A. Kumar and A. Leetmaa, 1994b: An experimental coupled forecast system at the National Meteorological Center: Some early results. Tellus, 46A, 398-418.

Reynolds, R.W. and T.M. Smith, 1994: Improved global sea surface temperature analysis using optimum interpolation. J. Climate, 7, 929-948.

Smith, T.M., A.G. Barnston, M. Ji and M. Chelliah, 1995: The impact of Pacific Ocean subsurface data on operational prediction of tropical Pacific SST at the NCEP. Wea. Forecasting, 10, 708-714.

Fig. 1. NCEP optimum interpolation (OI; Reynolds and Smith 1994) global SST anomaly field for the week of December 8-14, 1996.

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