HIGH WAVES IN THE NANSEI ISLANDS AND ITS DEPENDENCY ON TYPHOON TRACK

Abstract

 The Nansei Islands in Japan have been frequently hit by strong typhoons, causing significant damage due to high waves. On remote islands, precise forecast information is essential to protect people from unexpected high waves.Although the factors such as central pressure and wind speeds are already addressed in the wave forecast, the dependency of typhoon path on high waves needs to be more investigated because typhoons approach these islands from almost all directions. In this study, a statistical classification of typhoon path is proposed to quantify its dependency on high waves. In addition to the JMA typhoon best track data, measured wave data at the five ports of Naze, Naha, Nakagusuku Bay, Hirara, and Ishigaki derived from the NOWPHAS network were used as objective variables to apply multiple regression analysis among various typhoon parameters and wave heights at each location. The present analysis shows that there exists significant dependency in mean wave heights on typhoon path, suggesting that improvement of wave forecasting may be possible by incorporating such a typhoon path classification procedure.