textproduct: Tiyan

Marianas Update

A leading edge of a surface trough extending from distant Typhoon Dolphin (12W) continues to bring scattered showers and isolated thunderstorms to the region, carried by a moderate to strong westerly monsoon surge. Latest surface observations, radar and satellite analysis indicated that sustained winds have fallen below 30 mph. As such, windy conditions are no longer expected, so the Wind Advisory was cancelled earlier in the night. Otherwise, a Small Craft Advisory, High Surf Advisory and High Rip Current Risk Statement remain in effect for the Marianas.

Eastern Micronesia Update

A tropical ridge extending east from a buffer circulation over Kapingamarangi, will continue to produce a dry spell across the region for much of the forecast period. As such, the forecast remains unchanged. Continue to expect an extensive period of westerly swells as the monsoon trough remains anchored well north of Pohnpei, Kosrae and Majuro.

Western Micronesia Update

Similar to eastern Micronesia, a tropical ridge extending west from the aforementioned buffer circulation over Kapingamarangi in Pohnpei State, will continue to bring a drier regime across the region as most of the showers remain north of the main islands. As such, the forecast remains unchanged. Expect surf to continue building along north facing reefs of Palau and Yap over the coming days, as distant Typhoon Dolphin continues to head for Okinawa while producing pulses of northerly swell across the western Pacific.

Prev discussion

/issued 533 PM ChST Tue Aug 4 2026/

Marianas Synopsis... Satellite and radar observations show scattered to numerous showers and isolated thunderstorms. Sustained winds have been observed at 25 to 35 mph with gusts to 45 mph today. Altimetry and buoy data show combined seas between 8 to 11 feet.

Discussion... The monsoon surge that has brought strong to near gale winds to the Marianas over the last couple of days will persist tonight before beginning a weakening trend over the next couple of days. Although winds look to decrease towards the middle of the week, the monsoon looks to remain over the Marianas, keeping showers chances medium to high-end scattered (40-50%). The Wind Advisory remains in effect until 6 AM Wednesday. 20 to 30 mph winds with gusts to 40 mph will continue to be possible, especially in and around heavier showers. Winds look to decrease to 10 to 15 mph by Wednesday night as a short lull in higher winds moves over the region.

Towards the latter half of the week, into this weekend, and into next week, the forecast is dependent on the location and strength of newly designated Invest 96W located south of Wake Island. Invest 96W is currently weak with an elongated circulation, see the tropical discussion for more details. The westerly winds feeding into Invest 96W will intensify as the pressure gradient grows stronger. This will allow the monsoon to re-strengthen over the Marianas leading to a secondary surge. Uncertainty remains high on the placement of the monsoon surge. The GFS treats 96W more like a fully tropical system early next week, leading to stronger winds closer to the circulation and north of the CNMI. Meanwhile, the ECMWF has more of a subtropical appearance with the strong winds well south of the circulation, over the Marianas. The impacts would differ greatly with the potential for heavy rainfall and near gale winds near the center of the monsoon surge. A hydrological product may be needed in the coming days if confidence increases in the southern solution. Those in the Marianas should continue to monitor forecasts for updates in the progression of the monsoon.

Marine... Fresh to strong westerlies with occasional gale force gusts will continue through early Wednesday morning across the Marianas, especially near heavier showers. The monsoon looks to briefly weaken over the next couple of days, before reinvigorating later this week. A distant swell from Typhoon Dolphin (12W) continues to make its way into the region and will begin to shift from the north to the northwest. Meanwhile, a strengthening west to southwest swell will continue to impact our region over the next week. This combination in swells and wind waves will keep seas around 10 feet across the coastal waters, maintaining hazardous sea conditions for much of the week. A Small Craft Advisory remains in effect through early Friday morning.

A High Surf Advisory is in effect for west and north facing reefs, and a High Risk of Rip Currents is in effect for west, north, and east facing reefs of the Marianas. As monsoonal swells strengthen and period increases, surf could approach 12 feet across north facing reefs Wednesday night. A moderate risk of lightning is expected through the week.

Tropical Systems... A weak circulation, Joint Typhoon Warning Center's (JTWC) Invest 96W is centered south-southeast of Wake Island near 16N164E. Invest 96W is currently rated sub-low, meaning development is possible, but not expected over the next few days. 96W is expected to slowly move WNW over the next few days, with model guidance showing little, if any, development as it progresses. Invest 96W will be monitored closely over the next few days, but it currently does not appear to be a threat to the Marianas or Micronesia.

Eastern Micronesia... An abnormally dry regime has set up over eastern Micronesia, with little to no convection expected over the next several days. Kosrae looks to be the driest point, with several days, including the weekend, with POPs (Probability of Precipitation) less than 10 percent to near zero. Pohnpei and Majuro don't look to fair much better, with POPs remaining at or below 20 percent through the weekend.

For the marine forecast, expect gentle to moderate winds at Pohnpei to become light to gentle Thursday and continue through the weekend. For Kosrae and Majuro, light to gentle winds will prevail through the weekend. Combined seas look to remain fairly stable through the weekend as well.

Western Micronesia... A monsoon pattern remains north of the region, shifting slightly north away from Yap this afternoon. A trailing line of showers remains stretched out across eastern Yap State, otherwise relatively quiet weather persists for much of the region this week. Then, a southern bend in the monsoon trough brings a return to scattered showers at Chuuk late week.

Combined seas have increased to 5 to 7 feet, with seas up to 8 feet at Chuuk. Gentle to fresh southwesterlies are expected to continue at Palau, with moderate to fresh across Yap and Chuuk. As TY Dolphin passes to the distant north, north to northeast swell continues to build across Yap and Palau, shifting more northerly in the coming days. Elevated surf is expected this week along north-facing reefs, potentially becoming hazardous starting Wednesday night. Similarly, an increase in surf along west-facing reefs is expected as west to southwest monsoon swell builds. These trends in swell and elevated wind waves could see conditions approach hazardous levels for small craft in the latter half of the week for Yap.

GUM WATCHES/WARNINGS/ADVISORIES

GU...High Rip Current Risk through Saturday afternoon for GUZ001.

High Surf Advisory until 4 PM ChST Saturday for GUZ001.

Wind Advisory until 6 AM ChST early this morning for GUZ001.

MP...High Rip Current Risk through Saturday afternoon for MPZ001>003.

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

Wind Advisory until 6 AM ChST early this morning for MPZ001>003.

Marianas Waters...Small Craft Advisory until 6 AM ChST Friday for PMZ151>154.