Initial Wind Wave Sea Height Chart

Initial Wind Wave Sea Height Charts are historical wind-wave sea height charts. These analyzed charts cover the Northern Hemisphere (00 and 12 GMT) and were prepared by the National Weather Service, National Meteorological Center. The charts are stored on 35-mm microfilm. One year of charts corresponds to one reel of microfilm. The heights of wind-waves, swell, and combined seas are depicted by labeled solid contours at 3-foot intervals. Wave periods are plotted in seconds and are enclosed in circles at selected grid points. Wave direction arrows are drawn at the maximum wave centers. Other properties of wave height distribution may be inferred from the depicted significant wave heights (defined as the average height of the highest one-third of the waves). The chart on microfilm can be scanned into a paper or digital copy upon request.