Tropical Storm Choi-wan prompted tropical storm warnings across much of the Northern Mariana Islands on Thursday, October 1, as forecasters warned of damaging gusts, flooding rain and hazardous coastal conditions through the weekend.
In a local statement issued at 3:27 p.m. ChST, the National Weather Service office in Guam said a tropical storm warning was newly in effect for Agrihan and remained in effect for Tinian, Saipan, Alamagan and Pagan. A typhoon watch remained posted for Alamagan and Pagan and was added for Agrihan.
A warning means tropical-storm conditions are expected, generally within 24 hours. A watch means typhoon conditions are possible, generally within 48 hours. The labels describe different levels of confidence and timing; a watch is not a statement that typhoon-force winds are certain.
Where Choi-wan was and when conditions may worsen
At 2 p.m. ChST on October 1, the center of Choi-wan was near 16.8 degrees north and 147.5 degrees east, about 290 miles northeast of Guam. The storm was moving west-northwest at 18 mph with maximum sustained winds near 45 mph, according to the weather service.
Forecasters expected the system to slow and said it could strengthen into a typhoon by Friday afternoon. On Saipan and Tinian, tropical-storm-force winds of roughly 35 to 45 mph, with gusts to 60 mph, were forecast to begin Friday night and persist into Sunday. The strongest core could still track north of those islands, which is an important source of uncertainty.
Heavy rain, high surf and coastal flooding
The weather service projected 4 to 8 inches of rain for Saipan and Tinian through early Monday. Much higher totals were possible farther north: 8 to 14 inches around Agrihan and 10 to 16 inches around Alamagan and Pagan, with isolated totals near 20 inches close to the storm’s center. A flood watch for Saipan and Tinian was scheduled from 10 p.m. Thursday through late Sunday.
A later coastal hazard update issued at 8:43 p.m. ChST placed Saipan, Tinian and nearby islands under a coastal flood watch through Monday evening and a high surf advisory from 4 a.m. Friday to 4 a.m. Monday. Waves of 10 to 14 feet were expected along exposed reefs, with dangerous rip currents and localized coastal inundation possible.
What residents should do
People in the affected islands should use the latest official forecast for decisions, secure loose outdoor objects before winds increase, avoid flooded roads and stay away from wave-washed rocks and reef lines. Conditions and alert boundaries can change as the storm’s track becomes clearer.
Readers following Pacific weather can also see AskNovus coverage of heavy showers affecting Kauai and Oahu and visit the Weather section for additional verified updates.
Sources
- National Weather Service Guam — local statements and coastal hazards, October 1, 2026
- National Weather Service — current Saipan forecast and active alerts
- NMI News Service — local conditions report, October 1, 2026
Featured image: Josh Smith via Unsplash.