Area Forecast Discussion
Issued by NWS Tiyan, Guam
Issued by NWS Tiyan, Guam
609 FXPQ50 PGUM 120624 AFDGUM Area Forecast Discussion National Weather Service Tiyan GU 424 PM ChST Sat Jul 12 2025 .Marianas Synopsis... Mostly cloudy skies reign over the Marianas today. 0.5 inches of rain has fallen since midnight at the airport. Winds have been light with gusts to moderate. Altimetry shows combined seas of 3 to 5 feet, while the buoys 4 to 6 feet. && .Discussion... A wet and unsettled pattern is expected to continue for the weekend and the latter half of next week, with a short lull around Monday and Tuesday. TS 06W, located near the northern border of the AOR is pulling the trade winds into itself. This is causing a convergence zone over the Marianas and producing showers and thunderstorms. This zone will remain over the Marianas through the weekend. Then a short 24 to 36 hour lull in showers is anticipated due to TS 06W moving further away and the incoming monsoon trough building in. As the week progresses, models suggest that the eastern section will be forced northward. This northward trend is what will bring showers to the Marianas for the latter part of next week. && .Marine... Overall, fairly benign seas are expected for the Marianas. The surf is expected to be the highest along east facing reefs with a moderate risk of rip currents. On all other reefs, surf is expected to remain below 4 feet and the risk of rip currents will be low. Later next week, the monsoon flow may produce a southwest swell which could bring the surf up and possibly increase the risk of rip currents to moderate. && .Tropical Systems... A tropical disturbance remains southwest of Guam this afternoon. There is not a well defined circulation center, however, based on curvature shown in the visible satellite data, it is loosely located near 12N140E. Not much is expected from 94W over the next couple of days as it drifts west. Model guidance is in pretty good agreement that 94W will see little to no development over the next few days. && .Eastern Micronesia... The Inter-Tropical Convergence Zone (ITCZ) remains the primary player for eastern Micronesia. The ITCZ remains active, with scattered to numerous showers and isolated thunderstorms seen across the region. The majority of the convection is currently seen north of Majuro and south of Pohnpei associated with weak trade-wind troughs moving through and interacting with the ITCZ. This will continue to be the case for the next few days. A more robust trough looks to move into Kosrae Sunday night and Pohnpei Monday, bringing and extended period of numerous showers and isolated thunderstorms to both locations. Kosrae can expect the increase in coverage Sunday night through Monday night, with Pohnpei seeing the increase Monday and Monday night. The ITCZ looks to break down early next week, allowing POPs (Probability of Precipitation) to drop to around 20 percent Tuesday and Wednesday for Kosrae and Majuro and Wednesday for Pohnpei. Latest guidance indicates another burst in activity along the ITCZ by the end of next week. No major changes to the marine forecast. Mostly gentle to moderate winds are expected at Pohnpei and Kosrae, with occasional fresh winds possible early next week. For Majuro, moderate to fresh winds will become gentle to moderate late in the weekend. At Pohnpei and Kosrae, combined seas of 5 to 7 feet tonight will subside over the weekend, dropping to 3 to 5 feet Sunday night. For Majuro, combined seas of 6 to 8 feet will slowly subside over the next few days, becoming 4 to 6 feet by Tuesday evening. && .Western Micronesia... Palau and Yap: Similar to what`s been talked about the past few days, a southwesterly monsoon flow looks to develop in the next few days across the region. MIMIC PWATs are already in the 2.5 to 3 inch range with deep moisture saturation (surface to 50K feet), making for efficient rain-producers. Thus, some heavy rain concerns will potentially develop. For now, we increased shower coverage to numerous/likely for periods of time, especially at Yap as they`ll be better juxtapositioned for stronger surface winds and lift. Much of the upcoming week looks like "a wet one". Chuuk: A series of subtle trade wind troughs within the ITCZ will also allow persistent deep moisture transport with periods of increased lift. Here too, periods of numerous showers/likely probabilities will continue much of the week, with scattered shower coverage expected in between. && .GUM WATCHES/WARNINGS/ADVISORIES... GU...None. MP...None. Marianas Waters...None. && $$ Marianas: Bowsher East Micronesia: Kleeschulte West Micronesia: Doll