Scientific Forecaster Discussion
000 FXPQ60 PGUM 280737 AFDPQ Area Forecast Discussion National Weather Service Tiyan GU 533 PM ChST Fri Apr 28 2017 .Marianas Synopsis... Southeast winds prevail over the Marianas this afternoon. Low-level convergence will produce periods of scattered showers over Guam and Rota this evening. Isolated thunderstorms are possible across all the island through the night. && .Discussion... Afternoon satellite imagery showed a large area of scattered showers and isolated thunderstorms just northwest of the local area. Small segments of these showers were getting close to Guam and Rota and lightning was detected just to the northwest of Guam. While the large area of showers will remain north and northwest of the local area models hint at a brief period of scattered showers this evening near Guam and Rota. With the model and satellite data agreeing, added scattered showers to Guam and Rota through 12Z. Since lightning was detected have isolated thunderstorms through tonight for all the islands. Models agree on a return to a drier weather pattern with isolated showers expected through at least mid-week. Southeast winds will prevail through Saturday with east winds returning sometime on Saturday night. && .Marine... Scattered showers and isolated thunderstorms are expected in the Guam and Rota waters this evening, especially to the west of the islands. Isolated thunderstorms are possible through the whole night across all the coastal waters. Observations this afternoon from Ritidian, Tanapag, and Ipan buoys indicate combined sea heights around 4 feet. Expect combined seas of between 3 to 5 feet through the weekend. An east swell of 3 to 5 feet is expected through Tuesday. Tanapag buoy does show a northeast swell as does the WW3 model guidance. Model data indicate that this swell will end Saturday. Surf will be 5 to 7 feet on east facing reefs with little change the next few days. The surf on all other will be around 1 to 3 feet. Southeast winds will prevail through Saturday becoming east Saturday night. Wind speeds will be between 10 to 15 knots through Tuesday. && .Eastern Micronesia... In the near term, a disturbance to the east of Kosrae appears to be weakening and should have little impact on the area. However, scattered showers and isolated thunderstorms are developing further south between Kosrae and the equator and if these hold together, could bring rain to Kosrae later. Otherwise, an overall dry trade wind pattern is expected through Saturday night/early Sunday when another trade wind disturbance will bring a renewed chance of showers and thunderstorms, mainly for Kosrae and Pohnpei. This feature will move through by Tuesday, with a return to more isolated showers. && .Western Micronesia... The remnants of Tropical Depression Muifa are moving away from the region, but the area close to what is left of the circulation center still has plenty of showers and thunderstorms. South of the main center there were some scattered showers near Palau, and some isolated showers near Yap. Overall, rain chances should decrease, though there could be some afternoon convection over Palau on Saturday. Beyond that, a drier pattern appears to return. && .GUM WATCHES/WARNINGS/ADVISORIES... GU...None. Marianas Waters...None.