SAIPAN — The National Weather Service in Tiyan is tracking tropical disturbance Invest 99W as a developing monsoon pattern over Yap State drives scattered to numerous showers and isolated thunderstorms across the Marianas Wednesday and into Thursday, with Rota and Guam expected to see the heaviest activity.
The Marianas remain in the northeastern periphery of the unsettled pattern, NWS said in its morning forecast discussion. Showers are expected to build across converging monsoon and trade-wind patterns today and tonight.
Saipan and Tinian will see mostly cloudy skies, scattered showers, and isolated thunderstorms Wednesday, with highs around 86 and southeast winds 15 to 20 mph. The chance of showers is 50 percent. Lows tonight will fall to around 78.
Rota faces a heavier outlook, with numerous locally heavy showers and isolated thunderstorms, highs around 85, and occasional gusts to 25 mph near the heavier cells. The chance of showers on Rota is 70 percent.
Moderate southeasterly trade winds are expected to diminish to light-to-moderate starting Thursday. Combined seas of 5 to 7 feet are forecast, with a southwest swell expected to fill in over the next few days.
In Tanapag Harbor on Saipan, high tide was 2.2 feet at 4:30 a.m. Wednesday, with low tide of 0.2 feet at 11:32 a.m. and a second high tide of 1.7 feet at 6:26 p.m.