Area Forecast Discussion
Issued by NWS Tiyan, Guam
Issued by NWS Tiyan, Guam
285 FXPQ50 PGUM 172031 AFDGUM Area Forecast Discussion National Weather Service Tiyan GU 631 AM ChST Tue Jun 18 2024 .Marianas Synopsis... Satellite shows isolated showers moving through most of the Marianas Waters, with scattered showers in the southern Guam Waters. The Ritidian buoy reveals combined seas of 4 to 6 feet composed mainly of a moderate trade-wind swell and wind waves. && .Discussion... The disturbance is pushing out a little faster than anticipated, so trimmed the scattered showers a little. This placed them over the southern Guam Waters as opposed to over the island. This made it so the only forecast difference was slightly more clouds at Guam, so went ahead and recombined the zones, since weather is very similar over the remainder of the 7 day forecast period. This was the only change that made any significant difference. && .Marine... Combined seas of 4 to 6 feet will gradually diminish to between 3 and 5 feet by Saturday, and could reach 2 to 4 feet thereafter. This may be just enough to allow the risk of rip currents to diminish to low. Wind speeds are increased just a little this set of grids, around 2 or 3 knots for the first few periods. This is not enough to upset the benign marine conditions, which look likely to continue through the next several days at least. && .Eastern Micronesia and Chuuk... The Inter-Tropical Convergence Zone (ITCZ) remains across this area this morning, mainly between 4N and 8N, but it is less well-defined. Heavier showers are over Chuuk State, just west of Pohnpei, and along a surface trough that is moving from the Marshall Islands into Kosrae State. These heavy showers are in areas where low-level convergence is better focused, helped along with a divergent upper- level flow. The ITCZ and surface troughs moving across the region will cause areas of heavy showers and thunderstorms through this week, though minor shifts in the ITCZ may allow for periods of isolated showers. Combined seas of 4 to 6 feet are expected across the region, with some heavier conditions over the northeast Marshall Islands. Seas are not expected to change much this week as the trade swell is expected to change very little. Besides locally stronger gusts near showers and thunderstorms, winds will remain gentle to moderate this week, except becoming moderate to fresh at Majuro by Thursday. && .Western Micronesia... Only patchy showers and isolated thunderstorms are seen over Western Micronesia early this morning. ASCAT Winds analysis from last night indicated a surface trough stretches from the southern Philippines southeastward through a very weak circulation centered Southeast of Koror roughly near 6N136E then ending at about 4N142E. A surface trough also runs from near Yap to just southwest of Guam. The surface troughing pattern will likely persist over far western Micronesia during the coming days, and trade wind troughs could also push into western Micronesia from the east. Winds are expected to remain gentle to moderate, with winds at Yap mainly from the southeast, while Palau will be more variable, likely switching between southeast and southwest at times depending on how the troughs moves over the next few days. Marine conditions are not expected to change much this week. && .GUM WATCHES/WARNINGS/ADVISORIES... GU...None. MP...None. Marianas Waters...None. && $$ Marianas: Stanko Micronesia: Simpson