Early forecasts of the
sea state were created manually based upon
empirical relationships between the present state of the sea, the expected wind conditions, the fetch/duration, and the direction of the wave propagation. Alternatively, the
swell part of the state has been forecasted as early as 1920 using remote observations. During the 1950s and 1960s, much of the theoretical groundwork necessary for numerical descriptions of wave evolution was laid. For forecasting purposes, it was realized that the random nature of the sea state was best described by a spectral decomposition in which the energy of the waves was attributed to as many wave trains as necessary, each with a specific direction and period. This approach allowed to make combined forecasts of
wind seas and swells. The first numerical model based on the spectral decomposition of the sea state was operated in 1956 by the French Weather Service, and focused on the North Atlantic. The 1970s saw the first operational, hemispheric wave model: the spectral wave ocean model (SWOM) at the
Fleet Numerical Oceanography Center. First generation wave models did not consider nonlinear wave interactions. Second generation models, available by the early 1980s, parameterized these interactions. They included the "coupled hybrid" and "coupled discrete" formulations. Third generation models explicitly represent all the physics relevant for the development of the sea state in two dimensions. The wave modeling project (WAM), an international effort, led to the refinement of modern wave modeling techniques during the decade 1984-1994. Improvements included two-way coupling between wind and waves, assimilation of satellite wave data, and medium-range operational forecasting. Wind wave models are used in the context of a forecasting or hindcasting system. Differences in model results arise (with decreasing order of importance) from: differences in wind and sea ice forcing, differences in parameterizations of physical processes, the use of
data assimilation and associated methods, and the numerical techniques used to solve the wave energy evolution equation. In the aftermath of
World War II, the study of wave growth garnered significant attention. The global nature of the war, encompassing battles in the Pacific, Atlantic, and Mediterranean seas, necessitated the execution of landing operations on enemy-held coasts. Safe landing was paramount, given that choppy waters posed the danger of capsizing
landing craft. Consequently, the precise forecasting of weather and wave conditions became essential, prompting the recruitment of
meteorologists and
oceanographers by the warring nations. During this period, both
Japan and the
United States embarked on wave prediction research. In the U.S., comprehensive studies were carried out at the
Scripps Institution of Oceanography affiliated with the
University of California. Under the guidance of
Harald Svedrup,
Walter Munk devised an avant-garde wave calculation methodology for the
United States Navy and later refined this approach for the
Office of Naval Research. This pioneering effort led to the creation of the
significant wave method, which underwent subsequent refinements and data integrations. The method, in due course, came to be popularly referred to as the SMB method, an acronym derived from its founders Sverdrup, Munk, and Charles L. Bretschneider. Between 1950 and 1980, various formulae were proposed. Given that two-dimensional field models had not been formulated during that time, studies were initiated in the Netherlands by
Rijkswaterstaat and the (TAW - Technical Advisory Committee for Flood Defences) to discern the most appropriate formula to compute wave height at the base of a
dike. This work concluded that the 1973 Bretschneider formula was the most suitable. However, subsequent studies by Young and Verhagen in 1997 suggested that adjusting certain coefficients enhanced the formula's efficacy in shallow water regions. ==General strategy==