FXPQ50 PGUM 142028 AFDGUM Area Forecast Discussion National Weather Service Tiyan GU 628 AM ChST Wed Apr 15 2026 .Marianas Update... Typhoon Sinlaku is moving slowly and at times it has become nearly stationary. This is continuing devastating winds of 115 mph or greater over Tinian and Saipan. While heavy rain bands continue across Guam and Rota, bringing strong gusts to around 70 mph (see tropical systems section below). Due to the slow motion and large size of Sinlaku, the Flood Watch was extended through tonight. For Guam and Rota, westerly winds are driving the highest surf and inundation along west facing reefs and wrapping around to north and south facing reefs, while relaxing somewhat along east facing reefs. For Tinian and Saipan, winds have shifted to the southeast and south as the center is now west-northwest of the islands. This is placing the highest surf along east, south and west facing reefs, but at Sinlaku move away to the northwest, the northwest swell will increasing, rebuilding surf along north facing reefs across the islands. Coastal Flood Warning continues through Thursday morning, with High Surf Warning through Thursday afternoon. && Tropical Systems Update... As of 5AM ChST position and 1 AM ChST forecast from JTWC, Typhoon Sinlaku had max winds of 145 mph and was about 20 miles northwest of Tinian, 25 miles west-northwest of Saipan, 70 miles north of Rota, and 125 miles north-northeast of Guam. The forward motion was northwest at 5 mph overnight, but recent satellite imagery suggest forward speed has decreased again and Sinlaku was nearly stationary early this morning. This is keeping Saipan and Tinian near the eastern eyewall where devastating winds of 115 mph or greater are occurring, and potentially peaking at 145 mph. Rota and Guam are still well within the tropical storm force winds, with observations on Guam reporting winds around 46 mph with gusts of 71 mph, especially as heavy rain bands continue to move over the islands. It will take a long time for decrease in the winds across Guam, Rota, Tinian and Saipan due Sinlaku's slow motion and large size as tropical storm winds extend up to 265 miles from the center. Winds will be increasing at Alamagan, Pagan, and Agrihan as Sinlaku moves northwest, then northerly and passes to the west of the northern islands, bringing strong tropical storm and potentially low-end category 1 to 2 typhoon winds toward the end of the week. For more information, please refer to bulletins from the Joint Typhoon Warning Center (JTWC) under WMO header WTPN31 PGTW and from the National Weather Service under WMO header WTPQ31 PGUM and WTPQ81 PGUM. && .Eastern Micronesia Update... Satellite imagery this morning shows a broadly unsettled pattern across much of the Marshall Islands with numerous showers and isolated thunderstorms, while relatively quiet conditions near Pohnpei and Kosrae. The convection by the Marshall Islands looks to be along convergent flow that is along the trade winds around the Marshall Islands and the southwest flow south of Typhoon Sinlaku that still just pushing into Pohnpei. Scattered showers and isolated thunderstorms are seen south of Pohnpei and Kosrae, near the Equator, within the surface trough extending southwest from STY Sinlaku, passing near Chuuk and south of Pohnpei and Kosrae. The broad area of convergence will gradually shift northward with the movement of Sinlaku and fragmenting through rest of the week, maintaining scattered to numerous showers for the RMI, including Majuro, over the next few days, while relatively drier conditions persist for Kosrae and Pohnpei. Latest altimetry data shows 6 to 8 foot seas across much of the region. Elevated west to northwest swell will maintain elevated, potentially near hazardous surf along west and north facing reefs of Pohnpei through at least the next day or two. && .Western Micronesia Update... Satellite imagery shows partly to mostly cloudy skies across Palau, Yap, and Chuuk with showers still patchy as drier air is being pulled int the region south of Typhoon Sinlaku as it continues to move northwest just west of Tinian and Saipan. For Chuuk, northwest to southwest swell are keeping surf and seas elevated but so far model guidance and altimetry data suggest seas and surf below hazardous thresholds, and guidance supports a slow decrease in seas and surf as Sinlaku continues away and gradually weakens over the next few days. For Yap and Palau, marine and surf conditions will be the main concern this week. Large northeast swell from distant Typhoon Sinlaku continues to produce hazardous seas within Yap coastal waters and could peak around 11 to 13 feet before slowly tapering off on Thursday. A Small Craft Advisory remains in effect for Yap through Thursday afternoon. This long-period swell is also expected to bring hazardous surf along north and east facing reefs facing reefs of Yap, reaching to around 9 to 13 ft. Hazardous surf, combined with the higher high tides with the new moon cycle, there may be a concern for some minor coastal inundation along northern and eastern shorelines at times of high tide over the next few days. Hazardous surf has also developed at Palau along north and east facing reefs with surf around 9 to 13 feet. Similar to Yap, minor coastal inundation along northern and eastern reefs could also be an issue during high tide. && .Prev discussion... /issued 752 PM ChST Tue Apr 14 2026/ Marianas Synopsis... Super Typhoon Sinlaku is seen just south-southeast of Tinian and Saipan this evening. Tropical storm force winds continue across Rota and Guam, with typhoon force winds occurring at Tinian and Saipan. Sinlaku continues to slowly move toward Tinian and Saipan. Numerous to widespread locally heavy showers are seen across the Marianas, with isolated thunderstorms near the eye wall. Discussion... Not much has changed from the previous forecast. Super Typhoon Sinlaku continues to track toward Tinian and Saipan. Tropical storm force winds remain from south of Guam to the northern CNMI, with typhoon force winds over Tinian and Saipan. Winds will continue to increase at both Tinian and Saipan, reaching as high as 150 mph with gusts over 180 mph. Therefore, an Extreme Wind Warning was issued for both islands. This warning will be updated through the night until winds look to fall below 115 mph sustained. After eye passage at Tinian and Saipan, winds will gradually subside, but look to remain at or above tropical storm force through Thursday afternoon. For Guam and Rota, winds are peaking or have just peaked and will be slowly subsiding at both locations later tonight, though tropical storm force winds look to continue at Guam Wednesday evening and at Rota until after midnight Wednesday. After STY Sinlaku moves out of the Marianas, a dry pattern will move into the region and persist for several days after. Marine... Marine conditions remain dangerous across the Marianas. Seas have peaked over Guam and Rota waters and are expected to slowly subside over the next few days. Seas peaked in Guam at 26 feet, as shown by Ipan buoy in the early morning hours, while remaining around 25 to 30 feet in Rota waters. For Tinian and Saipan, seas continue to increase, with Tanapag buoy showing seas of around 26 feet, while altimetry shows over 35 feet to the east of the eye of Sinlaku. Seas look to peak for Tinian and Saipan at around 40 feet tonight, beginning to subside after Sinlaku moves farther north, away from the islands. Small craft advisory level seas to hazardous seas look to continue into the weekend, possibly falling below 10 feet for Guam and Rota early in the weekend and for Tinian and Saipan late in the weekend. Hydrology... The Ensemble Tropical Rainfall Potential (ETRaP) estimates from microwave satellite data shows that 12 to 20 additional inches of rainfall are possible near the center. With the past few forecasts supporting passage near or over Tinian and Saipan, these islands will have the greatest potential for that rainfall. Guam could still see a storm total of 6 to 12 inches, with Rota potentially reaching 10 to 20 inches. Flash Flooding is possible so a Flood Warning was issued for all 4 islands. Tropical Systems... As of the 700 PM ChST PGUA radar fix, Super Typhoon Sinlaku was centered near 14.7N 145.9E, or about 25 miles southeast of Tinian airport, 30 miles south-southeast of Saipan airport, and 115 miles northeast of Guam. The latest 6-hourly track shows a steady west- northwest motion of around 5 mph at 300 degrees, with the eye looking to move directly over or just south of Tinian. However, Sinlaku looks to be stalling just southeast of Tinian, remaining nearly stationary over the last hour or two. Radar reflectivity depicts the appearance of concentric eyewalls, with the primary eyewall around 10 to 15 miles across and the secondary eyewall around 50 miles across. Bands of high reflectivity and heavy showers within the outermost eyewall are rotating over Saipan and Tinian this evening as the center of Sinlaku stalls to the southeast, moving west to southwest across the islands. Saipan has begun to see sustained typhoon force winds of 78 mph gusting to 113 mph, while Guam is experiencing sustained winds around 50 mph gusting to 76 mph this evening. As Sinlaku nears Tinian and Saipan, winds will continue to increase, with very dangerous, rapidly worsening conditions tonight as the eyewall begins to move overhead, and sustained Category 4 typhoon force winds develop, with 130 to 150 mph winds gusting to 175 mph. Outside of the eyewall, the highest reflectivities and heaviest showers are presently seen in the outer rain bands between Guam and Rota, west and south of Guam, and just north to northeast of Rota within the secondary eyewall. The latest forecast track from the Joint Typhoon Warning Center (JTWC) maintains a north-northwest passage of Sinlaku over or near Tinian and Saipan late tonight with an increase in forward speed, but potentially passing directly over or south of Tinian if the current track observed on radar holds. Sinlaku's track looks to shift more northward after it crosses Tinian and Saipan, moving through the northern CNMI just west of Alamagan, Pagan, and Agrihan on Wednesday through Thursday night, before making a northeast turn away by the end of the week. Super Typhoon Sinlaku is on a gradual weakening trend through the next few days, but is expected to maintain Category 4 strength as it crosses the Marianas tonight. Eastern Micronesia... Satellite imagery late this afternoon shows a broadly unsettled pattern across much of the Marshall Islands and relatively quiet conditions near Pohnpei and Kosrae. Scattered to numerous showers and isolated thunderstorms are seen over much of the RMI including Majuro and Kwajalein Atolls, extending further northwest, passing west of Wake Island, within the broad, trailing convergence into Super Typhoon Sinlaku, far west-northwest of the region. Scattered showers and isolated thunderstorms are seen south of Pohnpei and Kosrae, within the surface trough extending southwest from STY Sinlaku, passing near Chuuk and south of Pohnpei and Kosrae. The broad area of convergence will gradually shift northward with the movement of Sinlaku and fragment through rest of the week, maintaining scattered to numerous showers for the RMI, including Majuro, over the next few days, while relatively drier conditions persist for Kosrae and Pohnpei. Latest altimetry data shows 6 to 8 foot seas across much of the region. Elevated west to northwest swell will maintain elevated, potentially hazardous surf along west- facing reefs of Pohnpei through at least the next day or two. Western Micronesia... Satellite imagery shows partly to mostly cloudy skies and patchy showers across the region as Super Typhoon (STY) Sinlaku continues to move across the Marianas, further distancing itself from the region. The Small Craft Advisory, High Surf Advisory, and the Coastal Flood Statement was allowed to expire for Chuuk as conditions are expected to gradually improve as Sinlaku moves further away. For Yap and Palau, marine and surf conditions will be the main concern this week. Large northeast swell from distant Super Typhoon Sinlaku continues to produce hazardous seas within Yap coastal waters and could peak around 11 to 13 feet before slowly tapering off on Thursday. A Small Craft Advisory remains in effect for Yap through Thursday afternoon. This long-period swell is also expected to bring hazardous surf along north facing reefs of Yap, possibly reaching hazardous levels of 12 feet for east-facing reefs. Hazardous surf, combined with the higher high tides with the new moon cycle, there may be a concern for some minor coastal inundation along northern and eastern shorelines at times of high tide over the next few days. Hazardous surf is also expected at Palau, likely reaching hazardous levels of at least 9 feet along north facing reefs and 12 feet along east facing reefs overnight. && .GUM WATCHES/WARNINGS/ADVISORIES... GU...Coastal Flood Warning until 5 AM ChST Thursday for GUZ001. Flood Watch through late tonight for GUZ001. High Surf Warning until 6 PM ChST Thursday for GUZ001. Tropical Storm Warning for GUZ001. Typhoon Watch for GUZ001. MP...Coastal Flood Warning until 5 AM ChST Thursday for MPZ001>003. Flood Watch through late tonight for MPZ001>003. High Surf Warning until 6 PM ChST Thursday for MPZ001>003. Typhoon Warning for MPZ001>003. Marianas Waters...Tropical Storm Warning for PMZ151. Typhoon Watch for PMZ151. Typhoon Warning for PMZ152>154. && $$ Marianas: Kleeschulte East Micronesia/Tropical: DeCou/Schank West Micronesia: Cruz/Schank IDSS: Mesa