Area Forecast Discussion
Issued by NWS Tiyan, Guam
Issued by NWS Tiyan, Guam
942 FXPQ50 PGUM 220644 AFDGUM Area Forecast Discussion National Weather Service Tiyan GU 444 PM ChST Sun Sep 22 2024 .Marianas Synopsis... Satellite and radar observations show isolated showers across the Marianas with scattered showers seen just to the east and southeast of Guam`s coastal waters. Ritidian and Tanapag buoys show combined seas between 2 and 4 feet. && .Discussion... A few changes were made with this forecast package. Scattered showers are expected to develop overnight and into Monday. Precipitation chances look to increase this week as a plume of moisture that is associated with Invest 91W move over the Marianas. A monsoonal-like pattern will set up across the Marianas with gentle to moderate westerly winds towards the middle of the week. At this time, the monsoonal pattern and Invest 91W appear to be little to low impact for the Marianas with low development chances. Please see the Tropical systems section for more details. Continue to monitor forecasts for any potential changes in the development of 91W. && .Marine... Seas look to remain benign with combined seas of 3 to 5 feet expected for much of the week at this time. Moderate to fresh winds of 15 to 20 knots may be possible as Invest 91W lifts away from the Marianas later this week. Although marine conditions look to remain calm this week, the forecast could change significantly depending on the development of Invest 91W. Continue to monitor forecasts for future updates. && .Tropical systems... Joint Typhoon Warning Center`s Invest 91W has moved rapidly northwest over the last 12 hours. Latest model guidance indicates that 91W will slow down considerably over the next couple days and approach the Marianas around Tuesday night or Wednesday. Models don`t favor much intensification of this circulation, with increased convection and winds of 20 to 25 mph possible around midweek as it passes through the Marianas. Invest 91W will continue to be monitored over the next few days. && .Eastern Micronesia... Eastern Micronesia has entered into an unseasonable dry period. This dry period looks to continue across the region into the weekend. As weak surface troughs move through the region, the islands could see brief periods of increased showers, though overall, look for POPs (Probability of Precipitation) to remain around 20 percent. No changes to the marine forecast. Combined seas of 2 to 3 feet will continue for Pohnpei and Kosrae, with 3 to 4 feet continuing for Majuro. Light to gentle trade winds will continue through the week. && .Western Micronesia... A broad west-southwest to east-northeast oriented trough stretches across western Micronesia and to the south of the Marianas, extending through JTWC`s Invest 91W near 12N152E. Satellite shows a region of scattered to numerous showers focused along the trough`s axis, mainly to the east-southeast of Yap and west of Chuuk. Based on model guidance and latest satellite trends, showers look to remain sparse for Palau and Yap this evening before becoming scattered at times overnight, and POPs were adjusted accordingly. The monsoon-like trough extending into 91W will linger over western Micronesia for the next few days before shifting northward during the mid-week, bringing gentle to moderate southwesterly flow over Palau and Yap. The associated convergence and moisture will yield on-and-off scattered showers throughout the week to both locations. Chuuk remains under the influence of a dry low-level ridge, and currently sits within the southwesterly flow to the south of the trough`s axis. Chuuk will remain fairly dry for the next few days, with a slight increase in showers for the latter half of the week due to a broad passing trade- wind trough. Marine conditions remain fairly benign. Babeldaob buoy data shows 1 to 3 ft seas near Palau, and altimetry data shows 2 to 4 ft seas just east of Chuuk. Light to gentle winds are expected throughout the week, with no marine hazards anticipated. && .GUM WATCHES/WARNINGS/ADVISORIES... GU...None. MP...None. Marianas Waters...None. && $$ Marianas: Williams Eastern Micronesia: Kleeschulte Western Micronesia: Decou