high wave advisory; high seas advisory
Official weather advisory issued when high waves are expected, typically by the Japan Meteorological Agency.
The Japan Meteorological Agency issued a high wave advisory for coastal areas.
波浪警報 is a higher-level warning for more severe wave conditions, while 波浪注意報 is an advisory for less extreme but still hazardous waves.
Compound of 波浪 (high waves) and 注意報 (advisory, warning).