Predicting significant wave height off the northeast coast of the United States

The significant wave height is the average height of the highest one-third of all waves and is a quantity that occurs frequently in air-sea interaction studies. To develop a simple method to predict the significant wave height, we analyzed 18 years of hourly observations from 12 different buoys that the U.S. National Data Buoy Center operates off the northeast coast of the United States. Water depths ranged from 19 to 4427 m for these moored buoys. We find that, on average, all of these buoys exhibit a region of constant wave height for 10-meter wind speeds between 0 and 4 m/s. That wave height did, however, depend on water depth. We presume that swell sets this minimum wave height, which ranges from 0.7 to 1.4 m. For wind speeds above 4 m/s, the wave height increases as the square of the wind speed, but the multiplicative factor is again a function of water depth. We have synthesized these results in a prediction scheme that yields the significant wave height from simple functions of water depth and 10-meter wind speed for wind speeds up to 20 m/s. Our method typically explains 50–60% of the variance in observed wave height.