AdvisoryExpired

Coastal Flood Watch · Guam · GU

NWS Tiyan GU · updated Oct 16, 2026, 05:12 UTC

What

For the High Surf Warning, dangerously large breaking waves of 7 to 9 feet Saturday afternoon, building to as high as 26 feet for Guam, 20 feet for Rota and 19 feet for Tinian and Saipan. For the Coastal Flood Watch, significant coastal flooding possible.

Where

For the High Surf Warning, initially east facing reefs of Guam, Rota, Tinian and Saipan; spreading to south facing reefs through Sunday afternoon. For the Coastal Flood Watch, all reefs of the Marianas.

When

For the High Surf Warning, from 5 PM Saturday to 4 AM ChST Monday. For the Coastal Flood Watch, from Saturday afternoon through late Sunday night.

Impacts

Numerous roads may be closed. Low lying property including homes, businesses, and some critical infrastructure may be inundated. Some shoreline erosion may 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. Coastal inundation of up to 5 feet for Guam, 2 to 4 feet for Rota and 1 to 3 feet for Tinian and Saipan is possible. Coastal flooding and beach erosion is possible.

Details

As TS Champi approaches the Marianas, surf conditions are expected to deteriorate rapidly, with surf reaching 9 feet Saturday afternoon, building to dangerous/deadly levels through Saturday night.

Saved source report · captured Oct 16, 2026, 09:02 UTC. Follow the issuing authority’s current instructions.