The National Weather Service (NWS) Guam Weather Forecast Office continues to monitor Invest 99W, a weak circulation southeast of Guam, which has been downgraded to a sub-low by the Joint Typhoon Warning Center. Despite the downgrade, computer models still show a disturbance forming south of Guam by midweek, bringing increased showers and gusty winds across the Marianas beginning Tuesday.
The Office of Homeland Security and Civil Defense (OHS-OCD) reports that heavy rainfall and near gale-force winds — up to 39 mph — are possible, with the peak expected around Wednesday or Thursday. Rainfall totals of 3 to 7 inches could occur between Tuesday and Thursday night, potentially leading to minor flooding and flash floods, especially in low-lying areas on Guam.
Residents are urged to clear drainage areas, monitor weather updates, and avoid flood-prone zones. Motorists are reminded to drive cautiously in heavy rain, watch for low visibility, and never attempt to cross floodwaters — as even six inches of moving water can be dangerous. OHS-OCD also warns of possible landslides in steep areas and advises reporting any signs of instability to authorities.
Weather conditions are expected to remain breezy and partly cloudy early in the week, becoming cloudier with scattered showers and isolated thunderstorms by midweek. The public is encouraged to follow the latest updates from the NWS Guam and GHS/OCD via their official websites and Facebook pages.