


Area Forecast Discussion
Issued by NWS Tiyan, Guam
Issued by NWS Tiyan, Guam
653 FXPQ50 PGUM 042012 AFDGUM Area Forecast Discussion National Weather Service Tiyan GU 612 AM ChST Sun Oct 5 2025 .Marianas Update... Looks like partly sunny skies and isolated showers are on tap for today in the Marianas, based on radar and satellite. We have the light winds for island convection, however it`s looking like we won`t get the sunlight required for island heating with the clouds that have moved in. The inherited forecast had already removed the island convection, so the only change made was to group the zones back together, since the biggest single reason for the zone split was now in the past. The other reason was winds 10 to 15 versus winds 15 to 20, so just called the winds 10 to 20. The buoys continue to show wave heights of 2 to 3 feet. && .Tropical Systems... The former Invest Area 94W has now been designated Tropical Depression 28W. Tropical Depression 28W is just barely within our Area Of Responsibility. It is forecast to move straight west, staying just within our AOR for at least a day or two. For additional information, please see the Tropical Cyclone Public Advisory issued by the National Weather Service under WMO header WTPQ31 PGUM and the Tropical Cyclone Warning issued by the Joint Typhoon Warning Center under WMO header WTPN31 PGTW. A tropical disturbance is now the subject of Invest Area 95W. 95W is centered near 7N154E. Currently, there is judged to be no chance for 95W to become a tropical cyclone within the next 24 hours. It is being watched for possibly future development outside of that time range. Information on 95W will be harder to come by until it actually starts to develop. && .Eastern Micronesia Update... There`s a lot of mid and high level cloudiness in Eastern Micronesia. The actual convection is mainly east of Majuro, with a smaller cluster between Majuro and Kosrae. So, today should actually be on the drier side. So the update was to lower the PoP`s to around 20 at Kosrae and Majuro, while retaining the partly sunny skies, since there are so many mid and high clouds floating around. At Pohnpei, retained the lower PoP`s, but raised the amount of clouds, as mid and high clouds are streaming in from the northwest. && .Western Micronesia Update... The forecast for Western Micronesia looked fine as was, so just reformatted to freshen up the date and time groups to say Today instead of Sunday, etc. A fairly wet week for Yap and Chuuk at least, and somewhat also Koror, but slightly less so. && .Prev discussion... /issued 812 PM ChST Sat Oct 4 2025/ Tropical Systems Update... Invest 94W is now the subject of a Tropical Cyclone Formation Alert, meaning tropical cyclone development is likely within 24 hours. The latest location for 94W is 23.8N and 143.3E, well north of the Marianas and east-southeast of Iwo To. Maximum sustained winds are 23 knots and the system is moving north-northwestward at 4 kt. For more information on Invest 94W, see bulletins issued by JTWC under WMO headers WTPN21 and ABPW10 PGTW. Prev discussion... /issued 524 PM ChST Sat Oct 4 2025/ Marianas Synopsis... Satellite imagery shows mostly cloudy skies, while radar imagery shows a few island effect showers near northern Guam. Buoy data shows sea heights of about 2 to 3 feet. Altimetry did not get a good pass near the islands today. Discussion... The Marianas is in the inflow convergence region of Invest 94W. Being in this region means as 94W strengthens so to will the change of showers increase. The island convection that was in the forecast has been removed due to the expected increase in cloud cover. Showers are expected to increase as Tuesday approaches. A trough is anticipated to pass over the Marianas then bring in high-end scattered showers and isolated thunderstorms to the region. Once this trough passes, pleasant weather may return. Marine/Surf... Combined seas of 2 to 4 feet and light to gentle winds are expected through at least Wednesday. There is a low risk of rip currents along all reefs through at least Wednesday. There also remains a moderate risk of lightning through at least Wednesday. Tropical Systems... Invest 94W is centered over the far northern CNMI near 23N143E. 94W is now rated as medium, meaning that development into a significant tropical cyclone is expected, but not within the next 24 hours. 94W is expected to continue to move west over the coming days as it continues to consolidate. Invest 94W will be monitored closely for the next few days. For more information on Invest 94W, see bulletins issued by JTWC under WMO header ABPW10 PGTW. Eastern Micronesia... A dry pattern has moved into Kosrae and Pohnpei for tonight, while Majuro is seeing scattered showers and isolated thunderstorms as a trade-wind trough approaches from the east. The Inter-Tropical Convergence Zone (ITCZ) has drifted north allowing a drier pattern to move into Pohnpei and Kosrae. This dry pattern will be short-lived as the ITCZ, though weaker, is expected to drop south while a weak trade-wind trough moves through. Scattered showers and isolated thunderstorms are expected to move into Kosrae Sunday and into Pohnpei Sunday night. Increased convection will continue at Pohnpei through most of next week as weak troughs continue to traverse the area. POPs (Probability of Precipitation) will range from 30 to 50% as the ITCZ wavers north and south. Kosrae will see a drier pattern return around the end of next week as the ITCZ moves out of the state. Majuro will see scattered showers and isolated thunderstorms through tonight as a trade-wind trough moves through and interacts with the ITCZ. For Sunday, scattered showers will continue, though will decrease. There will be a brief dry period for Sunday night, followed by another trade-wind trough bringing increased showers Monday and Monday night. By Tuesday, a dry pattern returns to Majuro and continues through the end of the week. Marine conditions are expected to remain fairly benign, with light to gentle winds and combined seas of 5 feet or less continuing through most of next week. Western Micronesia... Satellite imagery shows a broad trough gradually moving into Chuuk this afternoon. Late tonight and into Sunday, models continue to indicate some development with this feature as it slowly drifts northwest over the next day or so as a tropical disturbance. Unsettled weather is in store for Chuuk through Sunday or Sunday night, until the disturbance pulls away to the northwest, then scattered showers will continue through much of the upcoming week as a fragment of the ITCZ lifts northwest into the area. Meanwhile, patchy showers and light to gentle west to southwest winds over Yap and Palau are expected over the next couple days. Then, conditions begin to deteriorate Monday and Tuesday as distant Invest 94W and the aforementioned disturbance in central Micronesia support a southwest monsoon pattern over the region. Showers are expected to become numerous at times, mainly for Yap, with locally heavy showers possible. Scatterometry and altimetry data indicates benign marine conditions, light to gentle winds and combined seas of around 2 to 4 feet across the region. A pulse of southwest swell looks to build across Palau waters Monday, driven by a developing monsoon-like pattern, but no marine or surf hazards are expected at this time. Winds will remain mostly light to gentle, becoming moderate at times as the monsoon- like pattern strengthens. && .GUM WATCHES/WARNINGS/ADVISORIES... GU...None. MP...None. Marianas Waters...None. && $$ Marianas/East and West Micronesia/Tropical Update: Stanko Tropical Systems Update: Cruz Marianas: Bowsher East Micronesia/Tropical: Kleeschulte West Micronesia: Cruz