The diurnal and semidiurnal tidal constituents are calculated at Cobb seamount, latitude 46¿46.4'N and longitude 130¿48.8'W. The semidiurnal constituents agree with a model of Kelvin wave propagation north along the Pacific coast. The diurnal constituents do not agree with the Kelvin wave model. We also illustrate the application of an optimal interpolating formula to a time series consisting of the value and trend at each data point.