Area Forecast Discussion

Marianas Update

Models suggested, and so did altimetry, that seas were already below Small Craft Advisory criteria. So, went ahead and canceled that 12 hours early. Seas probably are high enough to support the high surf advisory for 12 more hours, so put that back out accordingly. Showers were sparse in the forecast today, and the radar shows they are in real life also. Verifying that trend, we only got a trace in the climate report yesterday. So, no other changes were necessary.

Tropical Systems

Typhoon In-fa has moved to near 21N143E. That is over 140 miles northwest of Agrihan Island in far northern CNMI. Wind speeds remain around 140 MPH and is heading west-northwest at about 22 MPH. In-fa is expected to turn to the north and decrease in forward motion.

For more information please refer to bulletins from the Joint Typhoon Warning Center under WMO header WTPN31 PGTW and from the National Weather Service under WMO header WTPQ31 PGUM and WTPQ81 PGUM.

Eastern Micronesia Update

No meaningful changes were need to the forecast. Isolated showers are expected over the region today, building to scattered for Pohnpei and Kosrae. Seas are expected to be 3 to 5 feet with light to gentle winds.

Western Micronesia Update

Just a rebalancing of showers this morning, done in accordance with satellite trends. Chuuk was isolated, so no changes were needed. Yap was isolated instead of scattered, so reduced the showers accordingly. and Palau was already scattered, so brought the scattered showers for the afternoon forward to the present time.

Prev discussion

/issued 541 PM ChST Fri Oct 30 2026/

Marianas Synopsis... Mostly high clouds are found over the Marianas this evening with spotty showers. Light to gentle winds prevail across Guam and Rota with gentle to moderate winds for Tinian and Saipan. Altimetry shows seas of 7 to 11 feet across the waters, with higher seas, in excess of 15 feet, north of Saipan.

Discussion... Not much has changed. A very dry pattern is anchored across the Marianas and looks to continue through the end of next week. The only exception is for Guam, during the afternoons of Sunday and Monday. With light and variable winds, island convection is expected for both afternoons, though Sunday looks to be the better chance out of both days. The one limiting factor will be the available moisture. However, after TY In-fa departs the region, it looks like PWats (Precipitable Water) will increase, possibly over 2 inches. This should allow the island convection to develop. If it does increase sufficiently and winds are light enough, the CNMI could also see some island convection. We should have a better idea tomorrow.

Marine/Surf... Large, long-period north swell emanating from TY In-fa will maintain seas up to 13 feet for Tinian and Saipan and up to 10 feet for Rota and Guam. Seas look to be the greatest as you go north, with southern Guam waters possibly seeing seas as low as 6 to 9 feet. This large swell will maintain hazardous surf for all the islands, mainly along north and east facing reefs this evening. Surf should begin to subside along east facing reefs later this evening as the swell becomes more northwest, while increasing to hazardous levels along west facing reefs. The large swell will subside by Saturday afternoon, allowing surf to fall below hazardous levels. The hazardous and elevated surf will maintain a high risk of rip currents along north and east facing reefs this evening, spreading to west facing reefs later in the evening.

Tropical Systems... As of 4:00 PM ChST today, Typhoon In-fa was located near 18.7N 146.2E, about 35 miles east of Agrihan and 375 miles north-northeast of Guam. Maximum sustained winds are 145 MPH, making In-fa a strong Category 4 typhoon with a west-northwest forward motion at 22 MPH. Destructive winds of 120 to 145 MPH with gusts to 180 MPH are most likely occurring over Agrihan as the island enters the western eyewall of In-fa. Further south, winds diminish, but are still destructive over Pagan and Alamagan. A partial eye passage is imminent over Agrihan as In-fa is forecast to maintain its current motion, emerging west of the far northern Marianas this evening and towards open ocean. Beginning Saturday, In-fa's forecast track becomes sporadic, but may continue to weaken over the next few days.

For more information please refer to bulletins from the Joint Typhoon Warning Center under WMO header WTPN31 PGTW and from the National Weather Service under WMO header WTPQ31 PGUM and WTPQ81 PGUM.

Eastern Micronesia... Fairly benign weather and seas will continue over the weekend, with brief periods of scattered showers for Pohnpei and Kosrae due to a reinvigorating segment of the monsoon trough shifting southward. Meanwhile, high pressure looks to set up over Majuro, so shower coverage will hover between 10 to 20 percent through the rest of the forecast period. Light to gentle winds will continue for all three forecast areas, with some periods of light and variable winds as diffusive flow occurs over the region. As the monsoon trough continues to re-establish itself next week, possibly south of 6N, the potential for showers could increase, especially for Kosrae. As of now, scattered showers and isolated thunderstorms are included to begin the work week.

Benign seas will continue through this weekend, with latest altimetry indicating combined seas of 3 to 5 FT across the region. Swells are 3 to 4 FT out of the north for Pohnpei, 3 to 4 FT out of the northwest for Kosrae, and 4 to 5 FT out of the northeast for Majuro. Then, distant mid-latitude features could emanate a long-period, north to northeast swell beginning next week, but surf and seas may remain below hazardous criteria.

Western Micronesia... A ridge extends across the southern half of the region, which points to light to gentle winds and a quieter weather pattern overall. However, afternoon visible satellite imagery shows spotty showers and a few thunderstorms across parts of Palau and Yap State due to the convergence between this feature and the monsoon trough just north of 10N. Additionally, island-effect showers did build across Palau earlier this afternoon. Showers that collapsed over Babeldaob sent out a small outflow boundary that enhanced a few thunderstorms near Koror. Continue to expected isolated to scattered showers for Yap and Palau this weekend and early next week, maintaining a special mention for island-effect showers and the potential for thunderstorms in the afternoon for Palau. Meanwhile, showers at Chuuk look to stay isolated, with a period of scattered showers as a trough builds in Sunday night.

Latest altimetry data shows combined seas of 3 to 5 feet. North to northeast swell emanating from Typhoon In-fa is expected to build seas to 4 to 6 feet across Yap and Palau over the weekend and next week, possibly reaching 7 feet at Yap early next week. Additionally, the long-period swell will also support elevated surf along north- facing reefs over the next few days, with wave model guidance showing a couple peaks in swell Saturday and starting around Tuesday. Meanwhile, seas and surf at Chuuk gradually trend down over the next few days as In-fa moves farther away, although northeast swell gradually builds into Chuuk State, keeping seas around 3 to 5 feet, possibly up to 6 feet around midweek.

GUM WATCHES / WARNINGS / ADVISORIES

GU...High Rip Current Risk until 4 PM ChST this afternoon for GUZ001.

High Surf Advisory until 4 PM ChST this afternoon for GUZ001.

MP...High Rip Current Risk until 4 PM ChST this afternoon for MPZ001>003.

High Surf Advisory until 4 PM ChST this afternoon for MPZ001>003.

Marianas Waters...None.