FXPQ50 PGUM 012046 AFDGUM Area Forecast Discussion National Weather Service Tiyan GU 646 AM ChST Wed Jul 2 2025 .Marianas Update... Increased the clouds a little, as satellite shows the outer clouds in the monsoon band moving through the forecast zones. Also lowered the combined seas/wave heights looking at the buoys and the ECMWFwave model data. This had the effect of lowering both the east and the southwest swells, which made the risk of rip currents low. && .Tropical systems... Tropical Depression 04W, formerly monsoon disturbance Invest 90W, is centered near 25N147E, moving north to northwest at 9 mph. At this time, maximum sustained winds are 35 mph near the center. 04W is forecast to intensify through tonight, possibly becoming a tropical storm as it exits the region sometime this afternoon. No direct impacts are expected to the Marianas or Micronesia from this storm. && .Eastern Micronesia Update... Isolated to scattered showers are seen across the region. Only minor adjustments were made with this forecast package. The main changes were to delay the start of scattered showers for Kosrae and Pohnpei. Kosrae currently sits in between scattered showers and isolated thunderstorms located towards the north and south. These showers and thunderstorms are forecast to increase in coverage later today as surface convergence from the fragmented ITCZ and a trade-wind trough move over Kosrae. Pohnpei has seen a decrease in showers this morning, but guidance shows a resurgence this afternoon due to a trade-wind trough moving through. Scattered showers were kept for Majuro through the day as satellite shows increasing coverage of weak showers across the RMI. Only minor edits were made to the Marine forecast. Swells were bumped down a foot for today to around 5 to 6 feet. Pohnpei's buoy shows that a good portion of the sea height is from wind wave, and a 6 foot swell may be on the high side right now. && .Western Micronesia Update... Satellite shows numerous showers southeast of Palau and scattered showers just southeast of Chuuk. Only minor changes were made with this update. The main one was to start Yap with isolated showers and thunderstorms. Models do show scattered showers and isolated thunderstorms moving into Yap later today. The scattered showers were kept for Palau and Chuuk today. For Palau, numerous showers and thunderstorms are seen well to the southeast, however some convection on the northern edge of the deep convection looks to move into the coastal waters in a few hours, this would bring scattered showers, with additional showers expected throughout the day. For Chuuk, scattered showers are seen just to the east of Weno with a stronger shower just southeast of the coastal waters. Guidance was in good agreement with increasing shower coverage by 00z. No changes were made to the marine forecast. && .Prev discussion... /issued 544 PM ChST Tue Jul 1 2025/ Marianas Synopsis... Satellite imagery and radar show isolated showers for Guam and Rota and scattered showers for Tinian and Saipan. Altimetry shows combined seas of 3 to 5 feet, while Ipan and Ritidian buoys show heights of 3 to 4 feet. Discussion... Scattered showers are seen just outside the Marianas waters. These showers are anticipated to build in overnight for much of CNMI, Guam is expected to remain in a clearer region. A break in the monsoon trough will give way to a drier next few days. Showers are anticipated to pick back up around the end of the workweek. Over the weekend, showers are anticipated to be minimal. Marine... Benign sea conditions are anticipated throughout the forecast period. Winds are expected to be light to gentle. Surf is the highest along east facing reefs. An incoming southwesterly swell is anticipated to arrive over the weekend. This may increase surf and rip current risk along south and west facing reefs. The risk of rip currents remains moderate along east facing reefs. Tropical systems... JTWC's (Joint Typhoon Warning Center) Invest 90W, currently showing a defined circulation center, but is roughly located well north- northeast of Saipan near 22.5N 148.2E, moving northward. Numerous showers and isolated thunderstorms are found to the east of the invest. 90W is now rated low, meaning it is expected to develop, but not expected to become a significant tropical cyclone within the next 24 hours. Although a closed circulation is not seen now, 90W is becoming more organized, with a TUTT cell near 21N145E providing divergent flow in the upper levels. Models do favor 90W developing into a more organized circulation as it continues north. For more information on Invest 90W, see bulletins issued by JTWC under WMO header ABPW10 PGTW. Eastern Micronesia... For now, the Inter-Tropical Convergence Zone (ITCZ) has weakened a bit, with less convection seen along the boundary. There is a flare up of convection with a trade-wind trough that is moving toward Kosrae. This trough looks to bring increased convection to Kosrae later this evening. Another weak trough is seen approaching Pohnpei and is expected to bring low-end scattered showers and possible thunderstorms to Pohnpei by midnight. Otherwise, the ITCZ is expected to strengthen a bit, with increasing showers spreading across the region. An overall unsettled pattern looks likely for the region as the ITCZ strengthens and weak trade-wind troughs move through. There will be brief periods of isolated showers through the week due to the wavering of the ITCZ and in between troughs moving through. No changes were made to the marine forecast. Combined seas of 5 to 7 feet at Majuro slowly subsiding over the next few days, dropping to between 3 and 5 feet for the weekend. Seas of 4 to 6 feet for Kosrae and Pohnpei could reach 5 to 7 feet tonight into Wednesday before subsiding to between 3 and 4 feet for the weekend. Gentle to moderate winds are expected through the week for Kosrae and Majuro, with gentle to moderate winds becoming light to gentle for Pohnpei Wednesday night. Western Micronesia... The wet, southwesterly monsoon pattern looks to continue for tonight with rounds of heavier showers and thunderstorms for both Yap and Palau. Could see fresh to potentially strong gusts with the bursts of showers. A surface ridge will try to creep west and may push the edge of the monsoon flow to the north and west of Palau and Yap, with generally isolated to low-end scattered showers expected through the end of the week. Through the weekend into early next week, may see the ridge break down over the region and a slow return to a wetter, monsoon-like pattern. Outside of gusty winds and choppy seas near heavier showers and thunderstorms, fairly benign marine conditions expected, with seas 3 to 5 feet and gentle to at times moderate winds will diminish slightly over the coming days as the monsoon swell and winds decrease. By late weekend into early next week, a longer-period northwest swell generated by a possible distant tropical cyclone developing northeast of the Philippines could build into the region, increasing seas ans surf. For Chuuk, a surface trough lifting northwest along the leading edge of a building ITCZ will bring increasing showers over the coming days. Expect isolated showers this evening to become scattered after midnight. High-end scattered to numerous showers and isolated thunderstorms are expected Wednesday through Thursday as the aforementioned features pass through. While coverage looks to diminish beyond Thursday as the trough pushes away and the ITCZ diminishes, are still expecting scattered showers and isolated thunderstorms into the weekend as subtle surface features pass through and weak east-southeast flow linger. Gentle to moderate winds are expected through Thursday. Fresh to potentially strong gusts are possible near heavier showers and thunderstorms as well. Winds look become light to gentle by Friday as the trough pushes west. Seas of 4 to 6 feet will be possible through Thursday night with the disturbance pushing through, then lowering around 2 feet by the weekend. && .GUM WATCHES/WARNINGS/ADVISORIES... GU...None. MP...None. Marianas Waters...None. && $$ Marianas Update: Stanko Tropical Update: Montvila East/West Micronesia Update: Williams Marianas: Bowsher East Micronesia: Kleeschulte West Micronesia: Slagle