A surf forecast or surf report is used to describe the wave energy, the wind conditions and the wave period. The wave energy (in kJ) explains the feel of the surf rather than just the wave height or the wave period. It explains the power of the predicted waves and may be the most useful guide to how engaging the surfing is likely to be at the surf spot. It is usually a dependent variable on both the wave size and wave period i.e. it has a direct proportional variation on the wave height and the wave period. It can be said that as wave size and wave period increase, the wave energy also increases exponentially.
The wave period (sec) on the other hand is the time space between two successive waves and it also has a direct proportion on the wave speed. Normally, wave periods not greater than 9sec are usually from locally generated winds and they don't produce a good surfingexperience.