Measured and hindcasted wave data samples in the coastal area of the Japan Sea during a huge low pressure system in April 2012 are analyzed. The results are that 1) frequent occurrence of large wave heights in recent years gives rise to an increasing trend of low-induced annual maximum wave height data samples at many of the measurement stations and results in augmentation of the return wave heights and their standard deviations, 2) wave models such as SWAN and authors's YH3 reproduce well the time variations of wave heights and wave periods during the low, 3) the low may yield a maximum wave height slightly exceeding 13 m in the Japan Sea, which probably corresponds to the uppermost value in the past 70 years, 4) a Monte-Carlo simulation suggests the likely occurrence of greater wave heights.
