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Summary of NCEP's Canonical Correlation Analysis (CCA), Optimal
Climate Normals (OCN), and Coupled Model Forecasts for U.S. Climate
contributed by Anthony Barnston
Climate Prediction Center, NOAA, Camp Springs, Maryland
Because the CCA (Barnston 1994) and ON (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 using forecast SSTs (Ji et
al. 1994), for Apr-May-Jun and Jul-Aug-Sep 1997 is provided. For more information about the
official NCEP forecasts, the following U.S. Re-gional 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 Apr-May-Jun'97
Temperature: OCN forecasts warmth in South-west, Northwest, and northern Appalachians; cold
Southeast. CCA predicts warmth in Texas, the Southwest, and southern Hawaii. The coupled
model dynamical forecast calls for warm in Pacific Northwest.
Precipitation: CCA predicts dryness South Texas, moist Pacific Northwest. OCN also forecasts
wetness in Pacific Northwest. The coupled model does not have usable skill for this season and
lead.
U.S. Surface Climate Forecasts for Jul-Aug-Sep '97Temperature: CCA predicts warmth
central Calif., southern Rockies, cool Midwest, Mid-Atlantic, New England. OCN predicts
warmth most of East and parts of West, cool midsection. The coupled model predicts warmth in
parts of Gulf Coast.
Precipitation: CCA and the coupled model have no usable skills for this period. OCN predicts
above median rainfall in Michigan and New Mexico, below median in northern Great Basin and
coastal N. Carolina.
Note: The above forecast descriptions include only regions whose estimated cross-validated
correlation 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 warming of the SST in Niño
3.4 (120-170oW, 5 oN-5 oS) to "high-neutral" by this spring, strengthening into moderate warm
episode conditions (with low confidence) by fall and continuing through winter 1997-98.
Specifically, CCA forecasts the following standardized anomalies and cross-validated correlation
skills:
forecast skill
Apr-May-Jun 1997 0.19 0.65
Jul-Aug-Sep 1997 0.72 0.31
Oct-Nov-Dec 1997 1.06 0.32
Jan-Feb-Mar 1998 1.44 0.45
Apr-May-Jun 1998 1.69 0.54
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 March
9-15, 1997 (Fig. 1) shows that the SST along the east-central equatorial Pacific has now increased
to the lower half of the near-normal range, with above normal SST in the east and at the date line.
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
subsur-face 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 March 9-15, 1997.
