Typhoon 9918 hit the Kyushu-Yamaguchi area early in the morning on September 24, 1999.This caused the serious damage and casualties in the area with strong wind, storm surge and high waves. The wave observation has been carried out at Kanda offshore wave observation station where the typhoon center passed nearby. Water surface elevation, pressure and water particle velocities were measured at the station during the typhoon passing. The wave data analyses as well as the directional wave analyses were carried out for the records. The record of the maximum significant wave height observed at the station was updated by this typhoon.
　In this paper, we investigated the severe sea conditions around the Kyushu-Yamaguchi area caused by the typhoon 9918 by using the wave hindcasting method. At the beginning of the investigation, the wind field was simulated by using the typhoon model (Myers' model) with appropriate parameters. Especially, the wind field on the Sea of Suou surrounded by the lands was carefully examined with the measured wind data, and was corrected in consideration of the influence of the lands. Based on the simulated wind field data, we simulated the sea conditions by using the third generation wave hindcasting model, WAM. As a results of the simulations, some characteristics of the sea conditions caused by the typhoon was clarified. In addition to the simulations with WAM, we also simulated the sea conditions by using the first generation wave hindcasting model, MRI, since it has so far been practically used for design of port and harbor structures in Japan. This paper discussed the accuracy and applicability of the WAM and MRI models based on the observed records such as wave heights and periods as well as the directional wave spectra.