information refer to the publication  Practical  Methods for  Observing  and  Forecasting  Ocean  Waves  (H.O. Publication 603), which gives the complete range of fu values and the corresponding periods for wind speeds, starting from 10 kt, at 2-kt intervals, Notice that the  frequency  decreases  as  the  wind  speed  increases, This suggests that the higher wind speeds produce higher ocean waves. The table mentioned above can be graphed for each wind speed, An example of such a graph can also be found in H.O. publication 603. It is difficult to work with actual energy values of these sine waves; for this reason the square of the wave amplitude has been substituted for energy. This value is proportional  to  wave  energy. The  square  of  the  wave  amplitude  plotted  against frequency  for  a  single  value  of  wind  speed  constitutes the spectrum of waves. Thus, a graph of the spectrum is needed for each wind speed, and the energy associated with each sine wave can be determined from these graphs.   Each   wind   speed   produces   a   particular spectrum; and the higher the wind speed, the larger the spectrum. FORECASTING SEA WAVES LEARNING  OBJECTIVES:   Describe   the generation  and  growth  of  sea  waves.  Explain the  formation  of  fully  developed  seas. Recognize the factors associated with nonfully developed seas, and determine and analyze features associated with sea waves. Define sea wave  terms  and  describe  an  objective  method of forecasting sea waves. Since  sea  waves  are  in  the  generating  area, forecasting of them will be most important when units are deployed in areas close to storm centers. Problems encountered in providing these forecasts will include accurately predicting the storm track and the intensity of the winds that develop the sea waves. Now let’s look at the generation and growth of sea waves. GENERATION  AND  GROWTH When the wind starts to blow over a relatively calm stretch of water, the sea surface becomes covered with tiny  ripples.  These  ripples  increase  in  height  and decrease  in  frequency  value  as  long  as  the  wind continues to blow or until a maximum of energy has been imparted to the water for that particular wind speed. These tiny waves are being formed over the entire  length  and  breadth  of  the  fetch.  The  waves formed  near  the  windward  edge  of  the  fetch  move through the entire fetch and continue to grow in height and period, so that the waves formed at the leeward edge of the fetch are superimposed on the waves that have come from the windward edge and middle of the fetch. This description illustrates that at the windward edge of the fetch the wave spectrum is small; at the leeward edge of the fetch the spectrum is large. These waves are generated and grow because of the energy transfer from the wind to the wave. The energy is transferred to the waves by the pushing and dragging forces of the wind. Since the speed of the generated waves  is  continually  increasing,  these  waves  will eventually be traveling at nearly the speed of the wind. When this happens the energy transfer from the wind to the wave ceases, When waves begin to travel faster than the wind, they meet with resistance and lose energy because they are then doing work against the wind. This then  explains  the  limitation  of  wave  height  and frequency that a particular wind speed may create. Fully Developed Sea When the wind has imparted its maximum energy to the waves, the sea is said to be fully developed. The maximum frequency range for that wind will have been produced by the fetch, and this maximum frequency range will be present at the leeward edge of the fetch. Once  the  sea  is  fully  developed,  no  frequency  is produced with a value lower than that of the minimum frequency value for the wind speed in question, no matter how long the wind blows. In brief, the waves cannot grow any higher than the maximum value for that wind  speed. When the sea is fully developed, the area near the windward edge is said to be in a steady state, because the frequency range does not increase any more. If the wind continues to blow at the same speed and from the same direction for a considerable period of time, the major portion of the fetch reaches the steady state. Nonfully Developed Sea When the wind is unable to impart its maximum energy to the waves, the sea is said to be nonfully developed.  This  can  happen  under  two  circumstances. First, when the distance over which the wind is blowing is limited or when the fetch is limited. Second, when the wind has not been in contact with the sea for a 6-5