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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 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 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 Jul-Aug-Sep and Jan-Feb-Mar 1998 are provided. For more 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 Jul-Aug-Sep '97
Temperature: OCN forecasts warmth in Florida and parts of East, and southern Nevada; cool
midsec-tion. CCA predicts warmth in East, parts of West, southern Texas, western Alaska and
Alaskan panhandle, southern Hawaii; cool Great Lakes, Midwest. The coupled ocean-atmosphere
model forecasts warm in Pacific Northwest.
Precipitation: CCA predicts wetness in Great Lakes/Northern Plains, northern Hawaii. OCN
forecasts dryness in North Carolina. The coupled dynamical model lacks usable skill for this
season and lead.
U.S. Surface Climate Forecasts for Jan-Feb-Mar '98Temperature: CCA predicts warmth
central Calif., Northeast, Great Lakes, Midwest, northern Plains; cold Hawaii. OCN predicts
warmth across the East and the West (especially the Southwest).
Precipitation: CCA predicts dry northern Plains, Great Lakes, Hawaii; wet Florida and southern
Texas, wet western Alaska. OCN forecasts dry in Ohio Valley, wet in portions of the South.
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
Jul-Aug-Sep 1997 1.05 0.62
Oct-Nov-Dec 1997 1.24 0.59
Jan-Feb-Mar 1998 1.68 0.64
Apr-May-Jun 1998 1.91 0.58
Jul-Aug-Sep 1998 1.39 0.30
The forecast for Jul-Aug-Sep 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 June 8-14,
1997 (Fig. 1) shows that the SST along the eastern and central equatorial Pacific has increased to
well above normal. Given that the "spring barrier" is largely out of the way for 1997, these
obser-vations strongly suggest a warm ENSO episode in the making for the remainder of 1997
and winter 1997-98.
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 June 8-14, 1997.
