FXPQ50 PGUM 191826 AFDGUM Area Forecast Discussion National Weather Service Tiyan GU 426 AM ChST Wed May 20 2026 .Marianas Update... The going forecast remains in good shape with no changes needed. The main focus continues to be on the high rip risk for east facing reefs, which looks to continue through Thursday afternoon. && .Eastern Micronesia Update... For Pohnpei, convection is located to your north and east, but very nearby to your area. An area of enhanced surface convergence is moving into the area and should act as a focus for numerous shower development. The going forecast has this well in hand, with the only changes made were to increase rainfall potential to 70 percent for today and tonight, while also lowering the afternoon high slightly. The current forecast at Kosrae and Majuro looks good with no changes made there. && .Western Micronesia Update... We lowered afternoon high temperatures at Palau and Chuuk for today, given the expected increase in cloud cover and convection. For Yap, a weak convergence pattern still favors scattered show potential, but minimal activity this morning casts some doubt. As such, we lowered rainfall potential there to 30 percent for today and tonight. otherwise, no other changes were needed. && .Prev discussion... /issued 547 PM ChST Tue May 19 2026/ Marianas Synopsis... Isolated showers and partly cloudy skies will linger for the Marianas through the next few days. Combined seas are 6 to 8 feet and a high risk of rip currents is in effect along east-facing reefs until Thursday afternoon. The region may see increasingly wetter conditions over the weekend. Discussion... The Marianas remains in a relatively dry trade-wind regime for the next few days. Satellite imagery shows partly cloudy skies and isolated showers that look to continue through tonight. A brief period in higher winds is in store for Wednesday as easterly wind speeds will be between 15 and 20 miles per hour with occasional gusts up to 30 miles per hour. As we enter the latter half of the week, overall conditions may start to shift on Thursday. Model guidance shows a slight decrease in trade winds and an increase from isolated to low-end scattered showers until the weekend. There is still support from the models for a wetter period starting this weekend through early next week, so chances of showers were adjusted higher to reflect that trend. A slight chance of thunderstorms remains in the forecast as models continue to depict either a surface trough or a potential disturbance originating in central Micronesia and shifting northwest, possibly impacting the Marianas beyond Memorial Day. This will continue to be monitored and communicated throughout the next several days. Marine... Combined seas of 6 to 8 feet are expected to remain through Thursday afternoon. Buoy data continues to support swells capable of producing surf up to 9 feet, and model guidance depicts little changes in the sea state for the next few days, so the high risk of rip currents along east-facing reefs is in effect until Thursday afternoon. Current model guidance shows wave heights to gradually decrease by a foot or two starting Thursday afternoon and continuing through the weekend. Eastern Micronesia... An increasingly unsettled, but disorganized pattern continues to build across the region. An Intertropical Convergence Zone (ITCZ) extends eastward across Pohnpei and Kosrae States from over central Micronesia, interacting with trade-wind troughs centered just west of Pohnpei, west of Kosrae, and with a very broad upper-level low located far to the north-northeast. Farther east, another ITCZ fragment builds just east of the Marshall Islands with a trade-wind trough propagating westward along it. These features are producing areas of numerous to widespread showers and isolated thunderstorms within eastern Micronesia. Pohnpei and Kosrae are situated on the northern periphery of the showers and thunderstorms associated with the ITCZ to the south, and Majuro sits along the very western edge of the advancing trough, ITCZ fragment, and associated convection. Numerous showers and isolated thunderstorms, with locally heavy rainfall possible at times, are expected for all three forecast zones for tonight, remaining numerous for Pohnpei and Kosrae through at least Wednesday, but tapering to scattered for Majuro for the next day or so. Models continue to be aggressive in depicting a very wet pattern throughout the week, and showers will likely increase to become widespread from time to time over the next few days, with little certainty in exact timing. The upper-level low north-northeast of the region is expected to remain semi-stationary as it weakens, extending westward as an open trough over the next few days. Despite weakening, the trough's position and orientation look to maintain good upper-level support for showers and thunderstorms across central and eastern Micronesia, mainly over Pohnpei and Kosrae States this week. Meanwhile, the ITCZ to the south looks to fragment and shift westward, helping to form a broad, disorganized disturbance across central Micronesia. Strong convergence upstream of this disturbance, with decent upper-level support, looks to maintain at least scattered showers across the region through the latter half of the week. Benign marine conditions are expected through the week. Latest altimetry data indicates combined seas between 6 and 7 feet across much of the region. Models depict a very gradual relaxation of the east to northeast trade swell throughout the week, allowing seas to diminish by a foot or so over the next several days. Western Micronesia... Satellite observations show scattered showers over Yap and Chuuk with isolated showers over Palau. Altimetry data shows combined seas between 4 and 7 feet. The robust convection that moved over Yap today has begun to wane, but scattered showers are still occurring beneath the warming cirrus. Across Chuuk State including Weno, scattered showers are seen from trade-wind convergence residing over the region. An active weather pattern will setup across much of western Micronesia over the next week. A monsoon-like trough is developing south of Palau and will intensify through the week. Eventually, this looks to become a full fledged monsoon trough this weekend or early next week. This monsoon- like or monsoon trough is expected to interact with a tropical disturbance as well. The combination of these two features will bring unsettled weather, beginning across Chuuk on Wednesday and then eastern Yap State this weekend and into next week. Uncertainty remains high with guidance split on whether there will be a northward pull of moisture, or if we'll see a more westward push. The former scenario would delay active weather for Yap Proper and Palau, but would keep them in westerly flow as the monsoon tail forms, placing a train of showers and thunderstorms over them. The latter scenario would shift the bulk of the disturbance over Yap and Palau, but would also exit the region faster. Currently, both the ECMWF and GFS deterministic favor scenario one with their respective ensembles closer to scenario one but more in the middle. The Canadian (CMC) and it's ensembles favor scenario two more. For now, the forecast tries to remain in the middle of these scenarios. Combined seas are between 4 and 7 feet across western Micronesia. On a broader scale, combined seas are expected to fall this week as winds begin to weaken due to trade-winds to the north and strong westerlies to the south; with the islands caught in between within a lull. Seas couldbecome elevated across Yap and Palau late in the forecast period as the potential monsoon trough builds into the region. && .GUM WATCHES/WARNINGS/ADVISORIES... GU...High Rip Current Risk through Thursday afternoon for GUZ001. MP...High Rip Current Risk through Thursday afternoon for MPZ001>003. Marianas Waters...None. && $$ Marianas/East and West Micronesia Update: Doll Marianas: Mesa East Micronesia: DeCou West Micronesia: Williams