Optimal tropical cyclone size parameter for determining storm-induced maximum significant wave height

Abstract

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The maximum significant wave height (Hsmax) induced by a tropical cyclone (TC) can be estimated from an empirical fetch formula using the TC’s size, maximum wind speed, and translation speed, in which larger, stronger, and faster-moving TCs generally have higher the Hsmax. In the formula, the radius of maximum wind (RMW) has been widely used as the TC size parameter under the assumption that Hsmax is mainly generated by strong winds near the RMW. This study investigates whether RMW is the optimal parameter for determining TC-induced Hsmax through extensive wave model simulations for North Atlantic hurricanes from 1988–2017. The correlation analysis between the estimated Hsmax and TC size parameters revealed that the radius of the 34-kt wind speed (R34, r = 0.84–0.95) was much higher than the widely used RMW (r = 0.33–0.58), which suggests that R34 is a more important TC size parameter for determining TC-induced Hsmax than RMW. This result can be explained by the fact that R34 showed a significantly higher correlation (r = 0.96) than RMW (r = 0.31) with cumulative TC wind speeds, which are closely related to Hsmax. These findings also indicate that the TC-induced Hsmax is more affected by the region containing moderately strong winds outside the TC than by the region of maximum wind speed near the RMW. Our paper provides additional insight into the mechanisms by which extreme wave heights, which cause severe damage during TC passage, occur.

Keywords

• maximum significant wave height
• tropical cyclone wind radii
• extended fetch
• parametric model
• fetch-limited growth
• the radius of maximum wind speed