Area Forecast Discussion
Issued by NWS Tiyan, Guam
Issued by NWS Tiyan, Guam
436 FXPQ50 PGUM 060818 AFDGUM Area Forecast Discussion National Weather Service Tiyan GU 618 PM ChST Thu Jun 6 2024 .Marianas Synopsis... Satellite imagery shows a mid to upper level low associated with the Tropical Upper Tropospheric Trough (TUTT) just to the east of Saipan and northeast of Guam. Otherwise, partly cloudy skies and isolated showers have persisted through the day. Altimetry data shows combined seas between 4 and 6 feet. && .Discussion... Not much change was made from the previous forecast. The TUTT is still positioned just east of the Marianas and is producing scattered showers and isolated thunderstorms near 15N150E and down to 12N152E. Current guidance has this meandering just east of the Marianas over the next few days keeping precipitation chances isolated. As we move into early next week, the TUTT should reposition itself into an orientation that favors divergence over the Marianas. This is when scattered showers and a slight chance for thunderstorms will be possible. && .Marine... Combined seas of 4 to 6 feet will diminish to between 3 and 5 feet by Saturday. Meanwhile, trade winds of 10 to 15 knots will diminish to around 10 knots around the same time. This will allow benign marine conditions to continue, the only exception being that around Tuesday we could see a moderate risk of lightning. && .Eastern Micronesia... Satellite this afternoon shows scattered showers and isolated thunderstorms building south and east of Majuro in an area of trade- convergence. Latest model guidance continues to build the Inter- Tropical Convergence Zone (ITCZ) south of Majuro by Friday to extend south of Majuro and Kosrae on Friday. The GFS is more robust than the ECMWF in building the ITCZ westward to north of Pohnpei during the same time frame. In either case, convergence along the ITCZ will generating periods of scattered showers and isolated thunderstorms through at least Saturday before the ITCZ fragments and dissolves around the beginning of next week. Benign seas conditions and light to gentle winds are expected through early next week at Kosrae and Pohnpei. For Majuro, benign sea conditions and gentle to moderate trades will give way to light to gentle trades this weekend into early next week. Altimetry passes this afternoon west of the Marshalls shows combined seas between 4 and 6 feet. && .Western Micronesia... The Tropical Upper Tropospheric Trough (TUTT) just west of Palau is generating scattered showers and isolated thunderstorms over Yap and Palau this afternoon. Shower and thunderstorm activity across Yap and Palau is expected to decrease as the TUTT cell moves west- southwest away from the region by Saturday. Model guidance from both the ECMWF and GFS both show a weak ridge setting up over Yap and Palau with weak trade-wind troughs rounding the periphery of the ridge, bringing periods of isolated to scattered showers through early next week. Benign seas conditions and light and gentle winds are expected to continue through early next week at Chuuk, Yap, and Palau. Altimetry passes this afternoon show combined seas between 3 and 4 feet. && .GUM WATCHES/WARNINGS/ADVISORIES... GU...None. MP...None. Marianas Waters...None. && $$ Marianas: Williams Micronesia: Kelly