PGUM issues Area Forecast Discussion (AFD) valid 2019-12-01T07:47:00Z 482 FXPQ50 PGUM 010747 AFDGUM Area Forecast Discussion National Weather Service Tiyan GU 547 PM ChST Sun Dec 1 2019 .Marianas Synopsis... Mostly cloudy skies with moderate trade winds and isolated showers prevail across the Marianas this afternoon. Scattered showers associated with a trade-wind surge are seen to the east of Guam and Rota waters. Latest buoy observations show seas between 10 and 12 feet at the Tanapag buoy and around 7 feet at Ipan. && .Discussion... The biggest change to the inherited forecast is in the short term. Scattered showers and isolated thunderstorms developed along the leading edge of a trade-wind surge this morning and moved in to Tinian and Saipan. These showers have since moved off to the west, while developing showers are now evident to the east of Guam and Rota waters. These showers are expected to increase in coverage and move across Guam and Rota through the night. The bulk of the activity is expected to remain south of Tinian, though isolated thunderstorms remain a possibility. A few weak outflow boundaries are evident on visible satellite data to the east of Tinian and Saipan. Although not expected right now, these features could produce a brief period of scattered showers for both islands later this evening. Drier conditions are then expected by Monday morning. A tropical disturbance near Chuuk is expected to move through to the south of Guam over the next couple of days. Although this system is expected to remain south of the Marianas, it could bring isolated thunderstorms to the islands again Monday night through Wednesday. By Wednesday night, a more stable pattern is expected to move in to the region. && .Marine... Large north swell continues across the Marianas waters this afternoon. Latest readings from the Tanapag buoy show seas between 10 and 12 feet. This swell is producing hazardous surf conditions for west and north facing reefs as well as a High Risk of Rip Currents. Surf is between 10 and 14 feet along north exposures and between 9 and 12 feet for west facing. The north swell is expected to subside through the night, dropping sufficiently to allow surf to fall below hazardous levels by Monday afternoon and the rip current risk to fall to moderate. At the same time, a trade-wind surge will result in increasing east swell. This swell will prolong the Small Craft Advisory criteria through Tuesday evening. Surf is not expected to reach High Surf Advisory levels, however, it will be sufficient to produce a High Risk of Rip Currents along east facing reefs, with possible wrap around effects on north facing reefs. && .Tropical systems... Typhoon Kammuri is well west of the Marianas. As Kammuri continues to move west toward the Philippines, large swell across the Marianas, Yap and Palau will continue to subside. This will be the last mention of TY Kammuri in the Tropical systems section. Another developing disturbance is centered near Chuuk at 7.3N 152.7E. This system is the subject of a Tropical Cyclone Formation Alert (TCFA) by the Joint Typhoon Warning Center (JTWC). Models indicate this system will track toward the west over the next few days with modest development. This disturbance is expected to approach Yap around Wednesday. Islands from Weno/Chuuk westward to Yap can expect periods of heavy showers, isolated thunderstorms, fresh to strong gusty winds, hazardous seas and hazardous surf. Inter-island travel is NOT recommended until conditions improve. Some of the locations that may be affected include, but are not limited to, the islands of Weno/Chuuk lagoon, Ulul, Satawal, Woleai, Fais, Ulithi and Yap. This system will be monitored closely over the next several days. For more information on the TCFA, see bulletins issued by JTWC under WMO header WTPN21 PGTW. A Special Weather Statement has also been issued by the National Weather Service under WMO header WWPQ82 PGUM. && .Eastern Micronesia... Fair weather persists across the Marshall Islands this evening and will continue through Tuesday night. Forecast models show a surface trough setting up over the Marshalls on Wednesday, moving slowly westward. This will bring the best chance of showers this week. Farther west, showers and thunderstorms are seen near Kosrae and Pohnpei. Kosrae and Pohnpei sit on the eastern end of a monsoon trough that reaches westward through the tropical disturbance centered near Chuuk. Showers and thunderstorms will persist at least through Monday when the disturbance moves west. GFS prolongs a showery pattern through midweek with a convergence zone/surface trough setting up over the islands. Significant weather is otherwise not expected in the region. Seas and surf continue to slowly subside across the region. Surf remains hazardous only at Kosrae along north and east facing reefs. Surf should fall below hazardous levels by Tuesday. && .Western Micronesia... A tropical disturbance near Chuuk remains the subject of a Tropical Cyclone Formation Alert by the Joint Typhoon Warning Center. See the Tropical Systems section above for more information and regional concerns related to this disturbance. This disturbance will head west, reaching Yap around Wednesday. Expect showers and thunderstorms to increase across Yap and Koror around midweek as the disturbance nears. Forecasts may change as this system evolves the next few days, so folks in Yap and Koror should keep a close watch on area forecasts. Fair weather today at Yap and Koror will continue across the region through Monday night. South to west winds will subside, becoming variable then shift to the northeast on Tuesday ahead of the approaching disturbance. A trade-wind pattern will set up across Chuuk behind the disturbance for the last half of the week. The High Surf Warnings at Yap and Koror are no longer in effect as surf has fallen below 15 feet. Surf will remain hazardous at least through Monday night. Hazardous surf could be prolonged at Chuuk as the disturbance nearby passes through the state. && .GUM WATCHES/WARNINGS/ADVISORIES... GU...High Surf Advisory until noon CHST Monday for GUZ001>004. Marianas Waters...Small Craft Advisory until midnight CHST Tuesday night for PMZ151>154. && $$ Kleeschulte/M. Aydlett