Marianas Update
Showers overnight were a bit anemic for Tinian and Saipan, however, more are now on their way. Therefore left the forecast in place, feeling that it would verify in the medium term, if not the short term. Therefore, no changes were needed in the Marianas. Seas of 6 to 8 feet will gradually diminish, possibly reaching 4 to 6 feet as early as Monday or Tuesday.
Tropical Systems
There are two suspect areas in the West Pacific currently. Invest Area 98W is near Chuuk, around 8N150E. It is currently rated sub-low by the Joint Typhoon Warning Center, which means development is not currently expected, however it is being monitored. The models tend to wash 98W out in a couple of days, and it doesn't look all that great even now.
The other suspect area is Invest Area 97W, which is in the northern Marshall Islands, around 12N165E. It is currently rated medium by the Joint Typhoon Warning Center, which means development is expected, but not within the next 24 hours. The models do develop 97W, however they are all over the place when it comes to where it might head. We do know a strong sub-tropical ridge remains in place to its north, so a straight north track is unlikely to persist. For the near future, this will be the system to watch.
For more information on 97W, please refer to the Significant Tropical Weather Advisory from the Joint Typhoon Warning Center. This bulletin is available under WMO header ABPW10 PGTW.
Eastern Micronesia Update
Increased the clouds at Pohnpei today, from mostly sunny to partly sunny. Everything else seemed okay at this time, so no other changes were made. The main action is farther north with 97W. It should have little or no effect upon the Eastern Micronesia zones though. Winds and seas are not expected to pose a major problem to mariners.
Western Micronesia Update
No changes were needed in Western Micronesia, where Yap was pretty dry, Chuuk was fairly wet, and Palau is somewhat dry. As in Eastern Micronesia, winds and seas are not expected to pose a major problem for mariners.
Prev Discussion
/issued 541 PM ChST Thu Oct 22 2026/
Marianas Synopsis... Himawari visible satellite and Doppler radar imagery this afternoon show partly cloudy skies and isolated to scattered showers across the area. Buoy and altimetry data depict combined seas around 6 to 8 feet.
Discussion... The Marianas are situated on the northwest periphery of a broad, weak circulation, Invest 98W, centered between Satawal and Chuuk Lagoon near 8N150E. A trade-wind trough extends northward from Invest 98W, with numerous showers and isolated thunderstorms seen along the axis, approaching the islands from the east. Scattered showers and isolated thunderstorms are expected tonight as the trade-wind trough shifts westward into the area, supported in part by divergence aloft associated with an upper-level low and trough. Over the next few days, model guidance shows most of the showers and thunderstorms developing near Tinian and Saipan where the strongest convergence looks to set up, as Invest 98W slowly meanders westward south of the islands, and an attendant trough to its northeast moves through the area. Late this weekend into early next week, a quieter ridging pattern looks to move in behind 98W.
Marine/Surf... Gentle to moderate northeast to east winds will prevail across Guam and Rota waters though at least Friday night, and start to diminish Saturday as wind direction briefly shifts southeast. For Saipan and Tinian, winds will be moderate to fresh out of the east over the next few days with occasional strong gusts Friday as trade winds briefly surge across the far northern CNMI. Combined seas of 6 to 8 feet could briefly increase a foot tonight as the highest pulse of the northeasterly swell arrives then, for Tinian and Saipan waters. Seas look to diminish thereafter as this swell begins to weaken. Meanwhile, there will be a moderate risk of rip currents through the weekend, mainly along north and east facing reefs. There will also be moderate risk of lightning through at least Friday night, mainly for Tinian and Saipan.
Tropical Systems... Two Invest areas were opened by the Joint Typhoon Warning Center (JTWC) today. A weak tropical disturbance is located over the northern Marshall Islands near 11N167E, designated Invest 97W by JTWC as of 1000 AM ChST. Invest 97W is currently rated "low" for development, meaning development is unlikely within the next 24 hours. Latest Himawari visible satellite shows broad, patchy cloud cover across the region with convection focusing near the center of 97W. The animated satellite imagery loop, and latest scatterometry data this morning, depict a weak, but clearly visible surface circulation in the vicinity of Rongelap and Bikini Atolls. Although there are several weak circulations across eastern and central Micronesia, models favor 97W most for development, with latest guidance showing gradual organization over the next few days as it remains quasi-stationary, strengthening more this coming weekend as it begins to move north. It is too early to say much about the eventual strength or track as 97W is a newly-formed system, but it will continue to be monitored in the coming days.
To the west, a broad, elongated surface circulation is centered between Satawal and Chuuk Lagoon near 8N150E, now dubbed Invest 98W by JTWC. Scattered to numerous showers and isolated thunderstorms are seen across the area, mainly within the convergent south to southwest flow into the disturbance. Invest 98W looks to remain broad and disorganized as it shifts west through the next few days, maintaining a generally wetter pattern for Chuuk and the Marianas into the end of the week. Invest 98W is also rated "sub-low" by JTWC, as it is not expected to develop in the next few days.
If Invest 97W or 98W organize and become rated "low" or higher, additional information on these disturbances will be found in bulletins issued by JTWC under WMO header ABPW10 PGTW.
Eastern Micronesia... Scattered showers from the monsoon trough will continue through tonight for Majuro and possibly Pohnpei, but are expected to remain fairly light with no thunderstorms. Kosrae is seeing dryer conditions and this is expected to continue for the entire forecast period as the monsoon trough stays weak and generally to the north. Winds are becoming light by tomorrow over Pohnpei which may allow for some scattered island effect showers in the afternoon. Light to gentle winds over Kosrae will be steady until potentially increasing slightly to gentle to fresh Saturday. Majuro has the highest winds, with gentle to moderate winds expected most of the forecast period, potentially becoming fresh Friday night as the monsoon surge peaks nearby to the northwest and feeds into the developing Invest 97W. However, with this system staying north, both Pohnpei and Majuro will also stay generally dry with isolated showers with the exception of low-end scattered showers and isolated thunderstorms Friday night for Majuro and Sunday for Pohnpei.
For the marine forecast, combined seas of 5 to 6 feet will remain steady for Pohnpei and Kosrae through the whole forecast period. Majuro may see 6 to 7 foot seas this weekend due to increased choppy seas from the monsoon surge. Otherwise, seas will likely drop back down to 4 to 5 foot by midweek for Majuro.
Western Micronesia... The main focus continues to be on the "newly-minted" Invest 98W, currently located near Chuuk at 7.9N 150.0E. This feature looks to move off to the north-northwest with little development expected, as evident by model data and JTWC's (the Joint Typhoon Warning Center) "Sub-Low" rating. Still, it looks to keep a prolonged period of scattered showers and isolated thunderstorms going as rainfall associated with the circulation and it's "inflow" persists. Farther west, Palau and Yap can expect just isolated showers this forecast period.
Winds and waves will be highest with 98W, as waves from distant STY Champi continue to decrease. Overall, seas of 4 to 6 feet are expected at Yap and Palau under light to gentle winds. For Chuuk, moderate to fresh winds will become light to gentle by the weekend with seas of 5 to 7 feet decreasing a foot by early next week.
As a side note, Palau looks to see a continuation of light haze due to wildfire smoke from Indonesia, as evident in satellite imagery. This looks to improve slightly over the next few days as Champi moves farther away and weak easterlies move cleaner air into the region.
Gum Watches/Warnings/Advisories
GU...None. MP...None. Marianas Waters...None.
Marianas/East and West Micronesia/Tropical Update: Stanko Marianas/Tropical Systems: DeCou East Micronesia: Ogle West Micronesia: Doll