Apra Harbor, Guam

Tropical Storm Sinlaku (04W) continues to organize north-northwest of Chuuk. This system will continue to move very slowly in a west to northwest direction for another 24 to 36 hours, before increasing forward speed as it strengthens. The current forecasts have the system strengthening into a typhoon or stronger, and approaching the Marianas. The potential track takes TS Sinlaku into the Marianas, near Guam. However, models continue to show a slight spread where TS Sinlaku's track could shift slightly north or south, though these ranges are narrowing and will continue to narrow over the next 12-24 hours. A breezy, but relatively dry trade-wind pattern is in place over the Marianas, but as Tropical Storm Sinlaku closes in, conditions will deteriorate sometime around late Sunday. The Marianas should make preparations for the potential for Tropical Storm or Typhoon-Force winds, with the most likely time of Tropical Storm-Forced winds around Monday. For the far northern Mariana Islands, breezy and choppy sea conditions are expected late this weekend and inter early next week, with potential for Tropical Storm-Force winds around Tuesday. Locally heavy rainfall is likely with Tropical Storm Sinlaku. Models show the potential 10 to 15 inches near the center of TS Sinlaku, but if any of the islands will see this rainfall will depend on exact track of TS Sinlaku. Ensemble guidance shows broader potential for 5-8 inches across Guam, and 3-5 inches for Rota, Tinian, and Saipan, but higher rainfall totals may shift depending if the track of Tropical Storm Sinlaku shifts southward or northward. of rainfall to develop for Guam early next week

Tropical Storm Sinlaku (04W) continues to organize north-northwest of Chuuk. This system is currently moving very slowly in a west to northwest direction, and this trend is expected to continue for another roughly another 24 to 36 hours, before increasing slightly in forward speed. TS Sinlaku is expected to strengthen as it approaches the Marianas, possibly crossing Guam as a category 3 typhoon. Models continue to show a slight spread where TS Sinlaku's track could shift slightly north or south, though these ranges are narrowing and will continue to narrow over the next 12-24 hours. A breezy, but relatively dry trade-wind pattern is in place over the Marianas tonight, but as Tropical Storm Sinlaku closes in, winds are expected to increase with conditions deteriorating sometime late Sunday. The Marianas should make preparations for the potential for Tropical Storm to Typhoon-Force winds, with the most likely time of Tropical Storm-Force winds around Monday. For the far northern Mariana Islands, breezy and choppy sea conditions are expected late this weekend and into early next week, with potential for Tropical Storm-Force winds around Tuesday. This is expected to produce 15 to 20 inches of rainfall between Sunday night and Wednesday for Guam and Rota, with 8 to 15 inches expected for Tinian and Saipan. Widespread showers, torrential rain and scattered thunderstorms are expected as Sinlaku moves through the Marianas Tuesday through Tuesday night. As showers are likely to persist, consistent rainfall is likely to produce flash floods and saturate the soils enough to increase the chance for mudslides over central to southern Guam.

ESFGUM This Hydrologic Outlook is for Guam, Rota, Tinian and Saipan. Tropical Storm Sinlaku is slowly approaching the Marianas and is expected to strengthen, possibly crossing Guam as a category 3 typhoon. This is expected to produce 15 to 20 inches of rainfall between Sunday night and Wednesday for Guam and Rota, with 8 to 15 inches expected for Tinian and Saipan. Widespread showers, torrential rain and scattered thunderstorms are expected as Sinlaku moves through the Marianas Tuesday through Tuesday night. As showers are likely to persist, consistent rainfall is likely to produce flash floods and saturate the soils enough to increase the chance for mudslides over central to southern Guam. Residents of the Marianas need to closely monitor this developing situation as flood watches, advisories and flash flood warnings will likely be issued later. If living near streams and rivers, move items away from stream and river banks. Make sure storm drains nearby are not clogged, especially If living at low-lying areas.