3. Introduction of WAM
The WAMmodel is a third generation wave model which solves the wave transport equation
explicitly without any presumptions on the shape of the wave spectrum. It represents the physics of the wave evolution in accordance with our
knowledge today for the full set of degrees of freedom of a 2d wave spectrum. The model runs for any given regional or global grid with a prescribed
topographic dataset. The grid resolution can be arbitrary in space and time. The propagation can be done on a latitudinal  longitudinal or on a
carthesian grid.The model outputs the significant wave height, mean wave direction and frequency, the swell wave height and mean direction, wind
stress fields corrected by including the wave induced stress and the drag coefficient at each grid point at chosen output times, and also the 2d wave
spectrum at chosen grid points and output times.
The model runs for deep and shallow water and includes depth and current refraction.
The integration can be interrupted and restarted at arbitrary times. The source terms and the propagation are computed with different methods and time
steps. The source term integration is done with an implicit integration scheme while the propagation scheme is a first order upwind flux scheme. The wind
time step can be chosen arbitrarily.
Subgrid squares can be run in a nested mode. In a course grid run the spectra can be outputted at
the boundaries of a subgrid . They can then be interpolated in space and time to the boundary points of the fine subgrid and the model can be rerun on the
fine mesh grid.
Hasselmann in the MaxPlanck Meteorological Institute, Hamburg, originally developed WAM. Then
WAMDI group (The WAM Development and Implementation Group), headed by Hasselmann after years of researches and revision, announces the third
generation of this model. The document now applies the fourth revised edition (Gunther et al., 1992). Within the WAM model, the basic equation is wave
energy equation in relation to any specific spot on the sea surface, whose spectrum E (j
,l
, f,q
, t), where (j
,l
) are latitude and longitude of any specific spot on sea surface, is a wave field of twodimensional frequency (f) and direction (q
).

(2)
where (Cj
, Cl
, Cq
) are the phase speeds of wave energy propagation on (j
, l
, q
) coordinates, S_{in} is the wave energy influx transferred to waves from winds,
S_{ds} is the depletion flux of wave energy, and S_{nl} is the energy
propagation flux induced by the nonlinear effects caused by component waves.
CONCLUSION
The big significant wave height and swell associated with severe
tropical cyclones stand out as by far the most damaging among natural disasters. They must be regarded as a serious
threat to life and property in our coastal areas. Many disasters are involved in the formation and propagation of waves,
such as the strength and size of the storm, bottom conditions where the surge comes ashore, and the position of the
storm center relative to the shore. In addition the ecosystem, fishery industry, environment and tourism industry are
also impact from big waves and storm surge. With high concentration of population near the coasts, demand for
quantitative estimates of vulnerability to big waves and storm surges of different coastal stretches have increased
during recent years.

Wind speed and direction at 10 meters Significant wave height and direction
3 NOVEMBER 1997 TIME 18 UTC
Progress has been forecasting and warning in cyclone, it is still
inadequate. If we can forecast and warning this situation, it will reduce the damage of life and property.

REFERENCE
[1] Bretschneider, C.L., 1958: Revisions in wave forecasting: Deep and shallow water. Proc. 6th Int. Conf. Coastal Eng. , ASCE, 3067.
[2] Chao, Y.Y., 1993: Implementation and evaluation of the Gulf of Alaska Regional Wave Model. NMC OPC Office Note, 35pp
[3] Golding, B., 1983: A wave prediction system for real time sea state forecasting. Quart. J. R. Met. Soc.109, 393416.
[4] Gunther, H., K. Hasselmann and P.A.E Janssen, 1992:Report NO.4, The WAM Model Cycle 4, Edited by Modellberatungsgruppe, Hamburg.
[5] Hasselmann, K, 1962: On the nonlinear energy transfer in a gravitywave spectrum. 1. General theory, JFM, vol. 12, 481500.
[6] Peng, S.P., 1991: On the numerical prediction model of ocean waves caused he numerical prediction model of ocean waves caused by monsoon.M. S. thesis, National Cheng Kung University.
[7] Sverdrup, H.U. and W.H. Munk, 1947: Wind, sea and swell: Theory of relations for forecasting. Publication 601, Hydrographic Office, U.S. Navy, 50 pp.

