Unai Achugao, 110

Tropical Depression 04W continues to organize north of Chuuk. This system will continue to move very slowly northwest 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, as it passes by Guam to the south. At this time, at least Tropical Storm Force conditions are possible for Guam and Typhoon Force conditions aren't out of the question, especially for southern portions of Guam. Current forecast tracks from the Joint Typhoon Warning Center has the typhoon passing south of Guam. Additionally, locally heavy rainfall will develop. Initial indications are for 10 to 15 inches of rainfall to develop for Guam early next week, decreasing into the 4 to 8 inch range further north towards Saipan. Locally higher amounts are probable. WITH THAT SAID...this system doesn't look to affecting the Marianas until sometime in the Sunday afternoon through Monday afternoon time frame, with possible deteriorating conditions thereafter. NOW IS THE TIME to start preparations! Forecast uncertainty in track and timing remains!

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

ESFGUM Tropical Storm 04W, currently located north of Chuuk, continues to organize and strengthen as it moves slowly west-northwest at 3 mph. This system is expected to become a tropical storm over the next few hours, strengthening further the next few days. As we approach the weekend, forward speed of 04W will increase, allowing the leading edge of the system to start affecting the region by Saturday afternoon. This rainfall will then increase in frequency and intensity Sunday into Monday, and may continue through Wednesday. Current forecasts range from 10 to 15 inches across Guam, decreasing into the 4 to 8 inch range for Saipan, with locally higher amounts possible. Of course, this is all dependent on the eventual track and intensity of what is expected to be a typhoon or super typhoon as it passes through the region, with current forecast tracks keeping the center a little south of Guam. However, forecast uncertainty remains and further track changes are anticipated. NOW IS THE TIME TO START PREPARING for locally heavy rainfall and the effects of such, especially if you live in or near a poor drainage area. Please continue to monitor the forecasts for changes at www.weather.gov/gum, or follow us on social media.

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.