Guam, Northern Mariana Islands Coastal Flood Warning | Effective 04/13/2026 16:47

* WHAT...For the High Surf Warning, dangerously large breaking waves of 13 to 18 feet for Guam and 15 to 20 ft for Rota and 20 to 30 ft at Tinian and Saipan. For the Coastal Flood Warning, significant coastal flooding 1 to 3 ft for Guam, and 3 to 5 ft for Rota and 5 to 8 feet, potentially reaching up to 10 to 15 feet, for Tinian and Saipan. * WHERE...North, east and south facing reefs and shorelines of the Marianas. * WHEN...For the Coastal Flood Warning, until 5 AM ChST Thursday. For the High Surf Warning, until 6 PM ChST Thursday. * IMPACTS...Numerous roads may be closed. Low lying property including homes, businesses, and some critical infrastructure will be inundated. Some shoreline erosion will occur. Breaking waves can sweep people off jetties and docks, and into dangerous seas. Life- threatening swimming conditions and significant beach erosion can be expected. * ADDITIONAL DETAILS...As STY Sinlaku continues toward the Marianas, swell and surf will continue to build. This will maintain dangerous surf and coastal inundation as STY Sinlaku moves through the Marianas today through Wednesday. Inundation has already been reported at Inarajan Pools. Tinian and Saipan could see wave and wind driven surf push water on to land up to 10 to 15 feet higher than the water-level, especially along windward facing beaches and shores.