Chalan Piao, MP Weather

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Area Forecast Discussion National Weather Service Tiyan GU 624 PM ChST Tue Oct 27 2026

.Marianas Synopsis: Light to gentle north winds are visible over Guam and Rota this evening with gentle to moderate east-northeasterlies over Tinian and Saipan. Isolated showers remain over Guam and Rota with high-end scattered showers over Tinian and Saipan as a trough moves through slowly. Model and observation data indicate combined seas of 5 to 6 feet.

.Discussion: Isolated showers tonight across Guam and Rota are expected to continue for the whole forecast period with the exception of scattered island effect showers in the afternoon Wednesday. For the Tinian and Saipan, a trough will continue to move through the region and bring scattered showers and isolated thunderstorms tonight, becoming isolated Wednesday. Showers will likely remain isolated until Friday when scattered showers and isolated thunderstorms return upon the passage of Typhoon In-fa somewhere to the north through the far northern CNMI anywhere from just north of Saipan to Maug island. Showers for Tinian and Saipan will likely return to isolated for the rest of the forecast period by Saturday. Current Typhoon In-Fa is expected to make it's closest point of approach sometime Friday. Breezy conditions can be expected for Tinian and Saipan Friday with sustained winds up to 30 mph and gusts to 45 mph. The current JTWC track puts only a 10-20% chance of tropical storm sustained winds for Tinian and Saipan. This situation remains highly uncertain and will continue to be monitored closely for any potential changes. See the "Tropical Systems" section for more details.

.Marine: Gentle northeast winds will prevail across Tinian and Saipan through at least Wednesday night, while mostly light winds prevail over Rota and Guam. Scattered showers and isolated thunderstorms will be possible for Tinian and Saipan tonight as a trough moves through the region, with isolated thunderstorms possible for all islands Wednesday. Therefore, there is a moderate risk of lightning along the coastlines tonight for Tinian and Saipan, and all islands Wednesday. There will be a moderate risk of rip currents all week for north- and east-facing reefs due to a primary east-northeast swell and a secondary west-northwest swell that will become negligible by Wednesday. Combined seas are expected to waver between 5 and 6 feet through Thursday. By late Thursday, seas are expected to increase significantly and become hazardous ahead of Typhoon In-Fa that is anticipated to pass somewhere through the far northern CNMI between just north of Saipan to Maug island. Widespread seas of 10 to 15 feet are expected for Tinian and Saipan with seas potentially up to 20 feet possible if In-fa takes a more southern track. Seas of 10+ feet are also possible for Guam and Rota. Therefore, the surf will also be hazardous on all islands, particularity for north and east facing reefs.

.Tropical Systems: At 1 PM ChST, Typhoon In-fa was located 205 miles north of Enewetak, about 1265 miles east of Guam, near 14N162E. In-fa is nearly stationary, moving west at only 1 mph. Maximum sustained winds were 125 mph. TY In-fa is expected to move west through Thursday, then begin to turn west-northwest by Friday, heading toward the island of Pagan in the far northern CNMI. In-fa is expected to weaken slightly through tonight, then begin to strengthen again Wednesday. TY In-fa could become a Super Typhoon as early as Thursday, and reach the northern CNMI at that intensity Friday afternoon. Residents of Tinian, Saipan and the far northern CNMI should continue to monitor forecasts for any updates or changes and the possibility of any watches or warnings, as changes in intensity, track and timing will occur over the next few days. A significant shift south could bring TC conditions to Tinian and Saipan, though this is not expected at this time.

For more information on TY In-fa, see bulletins issued by the Joint Typhoon Warning Center under WMO header WTPN31 PGTW and by the National Weather Service under WMO header WTPQ31 PGUM.

.Eastern Micronesia: A fairly dry pattern is in store for eastern Micronesia through the weekend. Mostly clear skies are expected at Majuro and Kosrae tonight, continuing at Kosrae through Wednesday night. The most that can be expected for Pohnpei and Kosrae is only isolated showers through the weekend. For Majuro, the monsoon trough looks to drift west over the next couple days, with a band of weak convergence setting up briefly over Majuro. This is expected to bring scattered showers to the atoll Wednesday through Wednesday night. By Thursday, the dry pattern looks to return to Majuro.

For the marine forecast, nothing has really changed. Still looks like combined seas at or below 6 feet through the weekend. Gentle to moderate winds at Pohnpei will subside to light to gentle by Thursday, while light to gentle winds will prevail at Kosrae and Majuro through the weekend.

.Western Micronesia: The main forecast challenge continues to be any rainfall for Palau and Yap in the short term, as the monsoon trough remains overhead or very near here. However, the latest infrared satellite imagery shows rapidly warming cloud tops. A weak circulation that was near there the last 48 hrs has dissolved. As such, opted for just isolated showers through Thursday night. Thereafter, the southwest monsoon flow will briefly strengthen at Chuuk Thursday, associated with Typhoon In-fa. Then, it quickly (the monsoon trough and area of increased winds/surface convergence) peels west thursday night, arriving and Palau and Yap Friday into Saturday. This will need to be watched though (In-fa and the monsoon trough) as there's some concerns that In-fa could take a more southerly track then currently forecast, which could in turn prolong inflow-related convection.

Otherwise, seas of 3 to 5 feet will briefly increase a foot Friday, into Saturday, mainly near Yap, as In-fa passes through the northern CNMI, The winds will generally be light to gentle, albeit briefly higher at Chuuk Thursday as the southwesterly inflow into In-fa briefly strengthens.

Watches, warnings and advisories

GU: None. MP: None. Marianas Waters: None.