In a perfect world a wave looks very simple. The height of a wave is the total distance from it’s peak to it’s trough. The period is the time, in seconds, that it takes for a first then second wave to pass the same point. In other words the time in seconds between successive peaks or troughs. Interestingly for us as surfers this number is consistently related to both a swells speed and the depth of water in which it can start to react with the seabed. This makes it something of a magic number for determining how a swell will transform itself into surf at your beach (something we’ll continue to cover in detail) and at least as important as the height of the swell.
The direction is exactly as it sounds – the direction in which the swell is heading. This is typically expressed in compass points (North, East, South, SW) or degrees (180, 270) and, while there’s no absolute convention surf forecasters tend to talk about the direction the swell is coming from. So a south swell is one that is heading from the south to the north, it could also be described as having a direction of 180 degrees.