Estimation of wave characteristics during hurricane in the Hoian area, Central Vietnam

Abstract

The data of hurricanes crossed the coastline from 14 degree N to 17 degree N, in the vicinity of the Hoian coastline, from 1945 to 2003 were extracted from the National Weather Service, USA. The features such as velocity of forward motion and wind speed were considered. Radius of maximum wind speed was estimated using the Saffir-Simpson scale. The maximum significant wave height within the storm and its associated spectral peak period were estimated using the Young's model. Empirical expressions relating wave height, maximum wind speed and wave period during hurricane were derived. The computed results from Young's model were compared with the hurricane wave prediction techniques of SPM (1984). The design wave height for the hurricane condition for different return periods was obtained by fitting a two-parameter Weibull distribution. The study indicates that in all, 69 hurricanes occurred in the vicinity of the Hoian coastline during 1945 to 2003 (with an average of 1.2 times a year), among which include 36 typhoon with maximum wind speed (V sub(max)) greater than 33 m/s, 20 tropical storm with 17 m/s less than V sub(max) less than 33 m/s, and 13 subtropical storm with V sub(max) less than 17 m/s. Occurrences of hurricanes were mostly in September (26.1 percent), October (30.4 percent) and November (13 percent). In general, radius of maximum wind speed of all hurricanes was 34 km. The design wave height was 11.7 m for 1 in 100 year return period.