Area Forecast Discussion
Issued by NWS Tiyan, Guam
Issued by NWS Tiyan, Guam
496 FXPQ50 PGUM 040708 AFDGUM Area Forecast Discussion National Weather Service Tiyan GU 508 PM ChST Thu Jul 4 2024 .Marianas Synopsis... Satellite shows showers and isolated thunderstorms over large areas toward the west and southwest of Guam, between the Marianas and Yap, while upstream eastward only isolated showers area seen. Ritidian buoy showed combined seas around 4 feet, but seas could be a little higher toward the east and northeast. Surface winds are gentle to moderate over the region this afternoon. && .Discussion... The upper-level trough that supports deep convection and development of thunderstorms has drifted a little farther away toward the west today, but there is still just the possibility of thunderstorms near or just west of Guam and Rota overnight. Otherwise, models indicate a more seasonal type of moist flow developing over the Marianas next week. Also, unstable weather continues over Eastern Micronesia, and there will likely be disturbances passing by Guam just to our south in the coming days. && .Marine/Surf... Gentle to moderate trade winds and combined seas of 3 to 5 feet will continue. There will be a moderate risk of rip currents along east facing reefs of the Marianas through the middle of next week, and a low risk along the other reefs. There will be a moderate risk of lightning tonight, mainly near Guam and Rota. A more general risk of lightning is possible starting Sunday. Weather conditions could become a little more unstable next week. && .Eastern Micronesia... Satellite imagery shows numerous showers and isolated thunderstorms ongoing for Majuro and are approaching Kosrae. Widespread showers are expected across Kosrae tonight with numerous showers possible at Majuro. Current upper level observations align with the GFS showing a TUTT to the north of eastern Micronesia and an upper jet on the southern edge of the TUTT extending down to Majuro. The combination of the upper jet and upper divergence across eastern Micronesia has led to numerous to widespread showers and isolated storms today. This looks to persist into the night as the GFS digs the jet southward, farther into eastern Micronesia. The trade-wind trough that is the surface trigger for the storms will move west tomorrow while the upper jet and TUTT shift eastward. This will lead to quieter conditions for Majuro and Kosrae as we head into the weekend. The bulk of the showers and storms should move towards Pohnpei on Friday and Friday night before shifting west of eastern Micronesia on Saturday. Much of the weekend appears relatively quiet for the region before an increase in precipitation coverage is anticipated early next week. Seas are generally in the 3 to 5 feet range but should build into the 4 to 6 feet range this weekend into next week. A Small Craft Advisory is in effect for Majuro until 6 PM this afternoon for convectively induced gusty winds. && .Western Micronesia... Satellite imagery shows scattered showers and isolated thunderstorms across Yap and Palau this afternoon. This is mostly associated with the TUTT that is moving westward to the north of western Micronesia, and the interaction with a couple of trade-wind troughs that have a weak circulation embedded to the west of Palau. These features are expected to shift westward and conditions appear to quiet down at the synoptic scale heading into the weekend. There does appear to be some potential for island convection for Yap, Palau, and Chuuk with light winds up to 500 mb through the weekend. Showers and storm coverage looks to increase for Chuuk early next week as a trough moves in from eastern Micronesia. && .GUM WATCHES/WARNINGS/ADVISORIES... GU...None. MP...None. Marianas Waters...None. && $$ Marianas: Simpson Micronesia: Williams