waves in a given area typically have a range of sizes. for weather reporting and for scientific analysis of wind wave statistics, their size over a period of time is usually expressed as "significant wave height." this figure represents the average height of the highest one-third of the waves in a given time period (usually twelve hours) or in a specific storm system or event. given the variability of wave size, the largest individual waves are likely to be twice the reported significant wave height for a particular day or storm.