Updated: 7:00 PM ChST on November 01, 2014
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Area forecast discussion National Weather Service tiyan GU 310 PM chst Sat Nov 22 2014 Marianas synopsis... a TUTT passes east of the marianas along 150e. An approaching trade-wind disturbance just to the southeast of the forecast zones has all but dissipated. A much more substantial trade-wind disturbance lies over and to the north of Chuuk and Pohnpei. Much smaller and weaker trade-wind disturbances can be seen on satellite southwest of Wake Island. && Discussion... satellite trends and near term model guidance both suggest the bulk of the trade-wind disturbance and surge currently north of Chuuk and Pohnpei will pass to the south of Guam. System remains diffuse enough to suggest scattered shower coverage is not in the offing for Guam tonight or Sunday...but situation will have to be monitored. After this disturbance passes...follow on trade-wind disturbances will continue supplying low-level moisture through Tuesday. TUTT will be lingering in the vicinity...so will carry mostly cloudy skies and isolated thunder in the forecast tonight through Tuesday. Second half of the forecast period looks drier as trade-winds usher in a drier air mass. && Marine... latest altimetry and buoy readings initialize combined seas closely to gridded values between 6 and 7 feet. However...energy arriving at the buoys is more concentrated in north swell versus east swell...so bumped up north swell 2 feet and shaved a foot from east swell today and tonight. Change results in a 5-foot north swell...which is only a foot or so below the height necessary to generate high surf. Wave watch guidance suggests north swell have already peaked...so do not believe high surf is likely during the next couple of days. Winds were gusting to around 25 knots earlier this morning over the forecast zones but have decreased this afternoon. Low pressure developing south of Japan will be weakening the subtropical ridge during the next couple of days...so do not anticipate a Small Craft Advisory for winds either. && Eastern micronesia... a fresh to strong trade-wind surge is moving through the region this afternoon. The leading edge of the surge is just north of Pohnpei to just south of Kosrae. Scattered showers that were expected this afternoon at Kosrae did not materialize with most of the convection developing late and to the south of Kosrae...though isolated showers and thunderstorms do remain a possibility there through the evening as the surge continues to push westward. Scattered showers are now moving into Pohnpei waters and are expected to continue there until around midnight. A secondary surge is now moving in to the Marshall Islands... bringing another round of isolated showers and thunderstorms to Majuro. These showers are expected to move west of Majuro late this evening with a brief period of drier conditions moving through the region through Sunday night. A trade-wind convergence zone is now just east of the date line and is expected to move over the Marshalls early Monday and spread over Kosrae Sunday night and over Pohnpei Monday. This convergence will maintain unsettled conditions over Majuro until the end of the week. As winds weaken over Kosrae and Pohnpei by midweek...the convergence zone will begin to dissipate. This will allow drier conditions to set up over both locations Wednesday. Building trade-wind swells and wind waves will cause higher surf and rip current risks along the east facing shores of Kosrae state and the Marshall Islands during the next few days. However...surf heights for both places should stay below hazardous levels. && Western micronesia... a weak disturbance is moving through Chuuk this afternoon... bringing scattered showers to the state a little earlier than previously expected. The leading edge of a trade- wind surge will move into the state Sunday...maintaining scattered showers over weno through the day. Showers will quickly decrease over the state Sunday afternoon with drier conditions likely for a brief period Sunday night. For Monday...the trade- wind convergence pattern that will affect Pohnpei will likely bring another round of unsettled weather to Chuuk early next week. Dry conditions are expected to continue over Yap and Koror though Sunday night. Early next week...increasing trade-wind convergence will bring an increase in convection to the region. Most of the activity will remain north of Koror though isolated thunderstorms are a possibility....especially over the northern coastal waters. && Gum watches/warnings/advisories... GU...none. Marianas waters...none. && $$ McElroy/kleeschulte