National Weather Service United States Department of Commerce



There are three fundamental properties of ocean waves: height, period, and direction. Wave height generally refers to how tall a wave is from trough to crest, wave direction is the direction the wave is coming from, and wave period is the time it takes for successive waves to pass a fixed point, such as a buoy. The period is also directly related to how fast waves move, how deep they extend into the ocean, how much energy they contain, which, in turn, influences the size of breaking waves at the coast, and more. 

In addition, it is common for there to be multiple, coexisting wave groups that coincide at any given point in the ocean. For example, during the fall, we often see short period waves from the NE that develop behind cold fronts, which simultaneously exist with longer period waves from the SE from tropical systems. In the summer we often see short period waves from the SSW associated with the local winds, along with small SE swell associated with the offshore Bermuda High Pressure area. Some users may only be interested in short period waves because they present hazardous, choppy waves for smaller boats, others may take particular interest in the long period waves given the shoaling hazards they create near shore, while others may be interested in both.  The point is, no two wave systems are created equal, any wave system present may be hazardous or of interest to different marine groups, and therefore we feel we should not ignore them.


Animation from COMET showing multiple wave systems


Currently, the National Weather Service in Wilmington provides a range of wave heights (i.e. 4-6 feet) with no corresponding direction or period information. The wave height values we currently provide are “Significant Wave Heights”, which is the average height of the highest one third of all waves at a particular point or region in the ocean. Significant Wave Height is a fundamental variable of the sea state that our customers are used to seeing, and also something very accessible from buoys to help gauge the current sea state and the accuracy of a forecast. As such, the proposed Coastal Waters Forecasts maintains that variable, but also supplements it with wave detail as described above and provided in forecast

Please help us evaluate the effectiveness of the proposed addition of wave detail to our Coastal Waters Forecast in real time. Over the next several months, we will be listening to your feedback (link to alias) to see how viable this project may be in the long term.


Additional Related Resources


Nearshore Wave Prediction System (High Resolution Wave Model run by value added winds created by the meteorologists at NWS Wilmington, and the heart of our wave detail project)

COMET Modules on Wave Fundamentals

Product Description for Wave Detail in the Coastal Waters Forecast