An entire storm can be characterized by just two numbers: one related to the wave height and one to the wave period. It now becomes important to predict these values from other data - such as geographical and meteorological information. Figure 2.13 for ”Open Ocean Areas” and ”North Sea Areas” gives an indication of an average relationship between the Beaufort wind scale and the significant wave height H1=3 and the average wave periods T1 and T2, defined before.