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Area Forecast Discussion
Issued by NWS Tiyan, Guam
Issued by NWS Tiyan, Guam
985 FXPQ50 PGUM 292136 AFDGUM Area Forecast Discussion National Weather Service Tiyan GU 736 AM ChST Sun Jun 30 2024 .Marianas Synopsis... Satellite shows partly sunny skies and widely scattered showers moving through the Guam and Rota Waters, with mostly sunny skies and isolated showers moving through the Tinian and Saipan Waters. The Ritidian buoy reveals combined seas of 3 to 5 feet, composed of trade-wind swells of 3 to 5 feet and 2 to 3 foot wind waves. && .Discussion... The moisture for this week looks a bit more restricted than it did last week. Seems this is largely due to a, for now at least, less robust than previously expected appearance of the monsoon trough. While the current unfavorable state of ENSO can`t stop the monsoon trough, it can hamper and restrain it. So the trough will get here, but it`s starting to look like it won`t be this week. Still, some moisture is filtering up from the south, so rainfall should slowly increase, and then sometime later the trough itself will arrive. The latest data from the GFS shows a particularly favorable presentation on day 16, but of course many models will promise you the moon that far out, the point is, will it start to move forward, and if so when. At that time, if not earlier, we will be able to shed the drought designation. && .Marine... Combined seas will remain within the 3 to 5 foot range for the foreseeable future in the ECMWFwave model, while in the GFSwave model they start at 3 to 5 feet then gradually diminish toward 1 to 3 feet in the extended. Since historically the GFSwave has trended a bit low, leaned toward the ECMWFwave solution. Meanwhile, winds will be 10 to 15 knots pretty much the whole time, which will lead to benign marine conditions this week. Enjoy them while they`re here. && .Eastern Micronesia and Chuuk... Unsettled weather continues across most of the region due to an Inter-Tropical Convergence Zone (ITCZ) and upper-level support from a Tropical Upper-Tropospheric Trough (TUTT) to the north. Widespread showers and several thunderstorm clusters are found around the Marshalls, then a weakened segment of the ITCZ stretches north of Kosrae, across Pohnpei, and ending east of Chuuk. Last night`s scatterometry pass did capture outflow boundary winds reaching up to 26 kt, originating from strong, collapsed storms to the east. This matched well with yesterday`s forecast, however satellite imagery shows that showers have cleared for the most part for today and ITCZ showers will have a chance to rebuild tonight. Otherwise, no major changes to the forecast. This upcoming week, models show a fairly active ITCZ pattern as trade-wind troughs continue to propogate through, but subtle shifts in the boundary will also bring brief periods of fairer weather as well. Winds will generally be light to moderate, with fresh to strong gusts possible for Kosrae today, and Pohnpei through tonight. Combined seas of 3 to 5 feet for most of the region and up to 6 feet at Majuro. && .Western Micronesia for Palau and Yap... A tropical disturbance west of the region continues deliver abundant moisture and induce a broad area of convergence in far western Micronesia. Satellite imagery shows pockets of deep convection moving through the main islands of Palau and Yap this morning. Models guidance depicts unsettled weather, however poorly-organized over the next day or two, then quieter weather is expected for the remainder of the week as a weak wind pattern sets up with some subtle disturbances passing through and bringing scattered showers at times. Island-effect convection could also flare up at times next week under the weak wind regime. Wind are mostly light to gentle with fresh to strong gusts possible with heavier showers tonight for Yap and for Palau today. Buoys indicate seas between 2 to 4 feet and will remain fairly benign as the week progresses and swell and wind waves decrease. && .GUM WATCHES/WARNINGS/ADVISORIES... GU...None. MP...None. Marianas Waters...None. && $$ Marianas: Stanko Micronesia: Cruz