1. Day at which forecast loses useful skill (AC=0.6) N. Hemisphere 500hPa height calendar year means Forecast day 8.08d

2. Annual Mean 500-hPa HGT Day-5 Anomaly Correlation CDAS is a legacy GFS (T64) used for NCEP/NCAR Reanalysis circa 1995 2

3. 3 Time series of monthly mean anomaly correlations for 5-day forecasts of 500-hPa heights for GFS, ECMWF, UKMO, FNMOC, CMC, and the CDAS frozen model for last 5 years GFS – US Global model ECMWF – European Center global model UKMO – United Kingdom Meteorological Office global model FNMOC – Navy global model CMC – Canadian global model CDAS – base line global model from 1991 Northern Hemisphere

4. 4 Time series of monthly mean anomaly correlations for 5-day forecasts of 500-hPa heights for GFS, ECMWF, UKMO, FNMOC, CMC, and the CDAS frozen model for last 5 years GFS – US Global model ECMWF – European Center global model UKMO – United Kingdom Meteorological Office global model FNMOC – Navy global model CMC – Canadian global model CDAS – base line global model from 1991 Southern Hemisphere