Wind gustiness and wave growth

We have analysed the consequences of wind gustiness on the growth of wind waves. Two mechanisms have been identified that enhance the usual Miles generation. the first one arises from the non negativity of the Miles mechanism and it is present only during the mature stage of a storm. The second is associated to the non linear dependence of the friction velocity on the wind speed and it is active throughout a storm cycle. The consequences of wind gustiness are found to be a faster growth and higher fully developed conditions, the increase being up to 30% in wave height. These findings are applied to a severe Mistral storm in the Mediterranean Sea and a very strong event in the North Pacific ocean. Their application to wave modelling is discussed.