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Summary of NCEP's Canonical Correlation Analysis (CCA), Optimal
Climate Normals (OCN), and Coupled Model Forecasts for U.S. Climate
for Jan-Feb-Mar 1998
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),
are provided for Jan-Feb-Mar 1998. 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; then click on "predictions", then click on
"experimental long-lead".
U.S. Surface Climate Forecasts for Jan-Feb-Mar '98
Temperature: CCA predicts warmth in along the west coast, north central states and Great Lakes area, and the inner Aleutians, southern Alaska and Alaska panhandle; cold in Texas, the Southeast (as far north as Tenn. and Ark.), the coastal mid-Atlantic and Hawaiian islands. OCN predicts warmth across the West, the Southwest, the Southeast and mid-Atlantic regions. The NCEP coupled model using forecast SST predicts warm around the Great Lakes, in Virginia and in south-central Alaska and the Alaska panhandle; cold in southern Texas, the Florida Peninsula and in southwestern Alaska.
Precipitation: CCA predicts dry in Montana, the northern Plains, upper Great Lakes, Ohio Valley
and the Hawaiian islands; wet extreme south such as Florida, southern Texas and southern
Rockies, and southern Alaska and Alaska panhandle. OCN forecasts dry in Ohio Valley and in
Montana, wet in parts of southern Rockies, southern Plains and the eastern Gulf. The NCEP
coupled model using forecast SST predicts wet in parts of the Southeast (especially Florida).
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 continued extreme warmth of the SST in Niño 3.4 (120-170W, 5N-5S) this boreal winter, moderating to "regular strong" warmth by spring, dissipating by summer (with low confidence) and turning cool by fall and winter 1998-99. Specifically, CCA forecasts the following standardized anomalies and cross-validated correlation skills:
|
Predicted Period |
Niño 3.4 Forecast (std dev) | Estimated Skill (correl) |
| Jan-Feb-Mar 1998 | 3.01 | 0.94 |
| Apr-May-Jun 1998 | 1.80 | 0.64 |
| Jul-Aug-Sep 1998 | -0.20 | 0.34 |
| Oct-Nov-Dec 1998 | -0.90 | 0.37 |
| Jan-Feb-Mar 1999 | -1.10 | 0.42 |
The forecast for Jan-Feb-Mar 1998 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 Dec 7-13
1997 (Fig. 1) shows that the SST along the central and especially eastern equatorial Pacific
remains far above normal. Strong El Niño conditions for boreal winter 1997-98 and at least early
spring 1998 are highly likely.
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 December 7-13, 1997.
