Scientific Forecaster Discussion
000 FXPQ60 PGUM 231922 AFDPQ Area Forecast Discussion National Weather Service Tiyan GU 520 AM ChST Mon Jul 24 2017 .Marianas Synopsis... Light to gentle southeast to south winds with mostly cloudy skies prevail across the Marianas this morning. PGUA WSR-88D data shows isolated showers across the region. Latest buoy readings show seas between 2 and 4 feet. && .Discussion... No changes made to the inherited forecast. Isolated thunderstorms remain in the forecast for today and tonight. Models indicate that the ridging between the tropical systems to the north and the monsoon trough to the south will remain over the region through next weekend. This will promote partly cloudy skies and only a few showers for the next week. Southeast to south winds will gradually shift to the southwest over the next few days. && .Marine... A small southwest swell will arrive the next few days, but with Typhoon Noru expected to remain to the north for the remainder of the week, a building north to northeast swell is anticipated to move into the Marianas, becoming the dominant swell around midweek. If Noru continues to develop over the next few days, the north swell could build sufficiently to bring high surf conditions to the islands by the end of the week, especially for Tinian and Saipan. && .Eastern Micronesia... A robust trade-wind disturbance coupled with upper-level divergence is producing showery weather over the Marshall Islands and some of the far northern islands, and for Kosrae today through tonight at least. Slightly drier mid levels should provide mild weather for Pohnpei and Chuuk thru today, at least. As the disturbance moves west over the next few days, showery conditions will spread toward Pohnpei and Chuuk. Decreasing trade winds near midweek should allow conditions to improve from east to west across the region. Another trade disturbance currently upstream near 163W could move into Eastern Micronesia later this week. Surf conditions will need to be monitored carefully at Majuro. The astronomical high tide or King Tide cycle will affect the Marshall Islands for the next few days, and there are east-southeast swell and wind waves up to 6 or 7 feet. Surf along south shores will be higher than average and splashing waves could occur along coastal roads and near the airport. && .Western Micronesia... There are High Surf and Small Craft Advisory head-lines for both Koror and Yap. A monsoonal circulation, Invest Area 99W, remains northwest of Koror near 11N131E with a monsoon trough stretched across Yap to southwest of Chuuk. Heavier showers are developing southeast to south of Koror, otherwise extensive cloudiness with patchy showers and thunderstorms are over Yap State and the Republic of Palau. Model guidance indicates increasing southwest winds and waves across Palau toward Yap, along with periods of showers, today thru Tuesday. Invest 99W should eventually move farther north into the Philippine Sea, and its influence over the area should diminish by Wednesday. After midweek, a surface ridge and milder weather is expected. && .GUM WATCHES/WARNINGS/ADVISORIES... GU...None. Marianas Waters...None.