An Observational Analysis of Ocean Surface Waves in Tropical Cyclones in the Western North Pacific Ocean

Knowledge of ocean surface waves in tropical cyclones (TCs) is necessary to calculate air-sea exchanges of momentum and enthalpy for improved TC predictions. Here we use 24 years (1992–2015) of TC and significant wave height (SWH) observations in the western North Pacific to analyze storm-following waves within the TC. The SWH was composited according to the TC translation speed, U _h , and TC intensity based on V _m , the maximum 10-m wind speed. The results show that SWH is largely symmetrical for slow-moving TCs when U _h is less than 3 m/s and is asymmetric for faster-moving storms with larger waves in the right-front quadrant referenced to the TC heading. For a class of TCs translating at a medium U _h between 3 and 7 m/s, a little less than the waves' group speed, near resonance leads to strong asymmetry with over 50% of waves with SWH exceeding 7–8 m on the right-front quadrant. As V _m intensifies to 50 m/s and greater, extreme waves develop and become saturated: SWH ≈ 10–11 m, corresponding to when, as shown in previous studies, the momentum exchange coefficient C _D levels off while the enthalpy exchange coefficient C _k may increase. Over 80% of the saturated waves then reside in the right-front quadrant, indicating the quadrant's dominant influence on C _D and C _k . The medium-translating TCs were found to have a greater propensity for intensification than other types of TCs. Our results suggest a link between TC intensity, translation, and wave saturation and asymmetry in the right-front quadrant.