The medium range forecast model of the National Meteorological Center (NMC) has been integrated to produce winter and summer simulations. For the winter simulation, the model was initialized with the NMC analysis of 1200 UTC 15 December 1985 and integrated for 110 days to simulate the December–March period (referred to hereinafter as the DJFM simulation). For the summer simulation, the model was initialized with NMC analysis of 0000 UTC 1 May 1986 and was integrated for 110 days to simulate the May–August period (MJJA simulation). In each case, seasonally varying boundary conditions of sea surface temperature, soil moisture and sea ice were used. The computer code used was nearly identical to that used by NMC for the operational ten-day forecast during the period 16 April 1985 through 30 May 1986. Both simulations have been compared to the NMC analyses for the corresponding period. It was found that the model climatology, defined as the average over the last 3 months of each run, is similar to th... Abstract The medium range forecast model of the National Meteorological Center (NMC) has been integrated to produce winter and summer simulations. For the winter simulation, the model was initialized with the NMC analysis of 1200 UTC 15 December 1985 and integrated for 110 days to simulate the December–March period (referred to hereinafter as the DJFM simulation). For the summer simulation, the model was initialized with NMC analysis of 0000 UTC 1 May 1986 and was integrated for 110 days to simulate the May–August period (MJJA simulation). In each case, seasonally varying boundary conditions of sea surface temperature, soil moisture and sea ice were used. The computer code used was nearly identical to that used by NMC for the operational ten-day forecast during the period 16 April 1985 through 30 May 1986. Both simulations have been compared to the NMC analyses for the corresponding period. It was found that the model climatology, defined as the average over the last 3 months of each run, is similar to th...