A three-dimensional numerical model (POM) is implemented to examine coastal upwelling in the northern Japanese coastal region with the passage of Typhoon Oliwa in September 1997. Observed sea surface temperature (SST) decreased suddenly ranging from $-6;to;-7^{circ}C$ in the coastal regions, and such a SST decrease state lasted for more than ten days after the typhoon passed. The model successfully reproduces the observation and gives a clear explanation, the sudden decrease of SST occurred in the process of coastal upwelling with Ekman dynamics. The model also describes the sea surface cooling in the open ocean with vertical velocity.