Observations of Tropical Cyclone-Generated Directional Wave Spectra from Surface Buoys during the ITOP Experiment

As part of the Office of Naval Research-sponsored, 2010 Impact of Typhoons on the Ocean in the Pacific (ITOP) field experiment, two moorings, deployed nearly 750 km east of Taiwan in the Philippine sea, recorded the frequency-direction spectra during the passage of 4 major tropical cyclones (TC). The TCs included severe tropical storm Dianmu, Typhoon Fanapi, Super Typhoon Megi (the most intense TC of 2010), and Typhoon Chaba. Based on our observations, when the storms were further afield from the measurement location, the wave spectra tended to be bi-modal, with swell emanating from the most intense storm region (right side of TC), and with seas aligned with the local winds (or nearly aligned with some time lag due to turning of the wind direction). When storms were close to the measurement location, the wave spectra typically transition to spectrally broad, uni-modal seas. The evolution of frequency-direction spectra and spectral parameters are discussed in terms of the storm dynamics and the local evolution of air-sea interaction parameters. Features of the frequency-direction spectra are compared to the output of a 3G wave model.