Sea State Code

The WMO sea state code is a ten-step scale (0 to 9) that classifies the sea surface by significant wave height, adopted by the World Meteorological Organization for marine reporting. The bands are: 0 calm, glassy (0 m); 1 calm, rippled (0 to 0.1 m); 2 smooth, wavelets (0.1 to 0.5 m); 3 slight (0.5 to 1.25 m); 4 moderate (1.25 to 2.5 m); 5 rough (2.5 to 4 m); 6 very rough (4 to 6 m); 7 high (6 to 9 m); 8 very high (9 to 14 m); 9 phenomenal (over 14 m). It describes the height of wind sea, not the wind itself, so it complements the Beaufort wind scale and feeds ship weather reports and routing.