Using an operational numerical weather prediction model at the Japan Meteorological Agency, i.e., a 6-level, fine-mesh, limited area primitive equation model, a preliminary study was made with regard to the numerical simulation of synoptic scale atmospheric motion during the AMTEX '74 period. As the first phase of the investigation, three cases are taken up for the case study. The first case (Case 1) shows the passage of a moving anticyclone and a cyclone over the East China Sea. The second case (Case 2) is the case of a front passage in the Okinawa area. The third case (Case 3) is featured by the predominant coverage of the whole AMTEX area by a cold air mass. Calculated patterns of the three cases show, in general, good agreement with observed patterns. The second phase of the investigation elaborates comparison of the synoptic scale sensible and latent heat supplies from the sea surface in the model atmosphere in the cases mentioned above. The bulk aerodynamic method is employed for the estimatin of the sensible and latent heat supplies which are quite sensitive to the synoptic situation. The model atmosphere also well simulates the day-to-day variation of the supplies. The hour-to-hour variation in the model atmosphere, however, is not moderate as in the case of the real atmosphere, but shows a sharp decrease in the intensity as time advances. This may be a deficiency of the model in responding to external heating. The calculated total quantity of heat supplies during 24 hours compares favorably with the preliminary calculation of heat supplies from the AMTEX '74 observation by J. KONDO (1974). A comparison is made between the 24-hour forecast wit h the normal sea 'surface temperature and that with the 8-day mean sea surface temperature of 87-28 February 1974. No appreciable difference is seen in prognostic patterns ofmeteorological variables such as pressure, wind velocity, temperature, humidity and quantity of precipitation as far as the 24-hour forecast is concerned. However, the distribution of sensible and latent heat supplies shows a significant discrepancy between the two cases.