Area Forecast Discussion
Issued by NWS Tiyan, Guam
Issued by NWS Tiyan, Guam
046 FXPQ50 PGUM 260843 AFDGUM Area Forecast Discussion National Weather Service Tiyan GU 643 PM ChST Sun May 26 2024 .Marianas Synopsis... Satellite imagery is showing partly cloudy skies and isolated showers moving west from Tinian and Saipan, with mostly clear skies over Guam and Rota. Latest altimetry data is indicating seas of 3 to 5 feet in the coastal waters. && .Discussion... Mostly clear skies and dry conditions over the Marianas this afternoon with CIMSS MIMIC precipitable waters values around 1 to 1.25 inches in the region. An approaching weak disturbance will bring increasing clouds and isolated showers later tonight and into tomorrow. Otherwise, expect slight upticks in clouds and showers through the week as ripples in the trades pass through. Some guidance is suggesting the flow turning more southerly and drawing deeper moisture from Micronesia across the region, with an increase in clouds and showers expected. For now, confidence is too low this far out and capped Probability of Precipitation (POP) at 20 percent and sky cover partly cloudy. && .Marine... Fairly benign marine and surf conditions this week with a slightly elevated trade swell impacting the waters. A background north to northwest swell emanating from distant storms may pass through the waters around mid to late week. Gentle to moderate trade winds expected through most of next week. Sea heights 3 to 5 feet look to rise about a foot Monday through Tuesday, then drop back down to 3 to 5 feet by Wednesday. A moderate risk of rip currents continues along east facing reefs, with a low risk along south, west and north facing reefs. && .Eastern Micronesia... Convection across the region and just east of the Date Line has diminished through the day, and showers are isolated across Pohnpei, Kosrae, and Majuro. A weak trough is currently passing near Kosrae and models show convection redeveloping along the trough later tonight bring scattered showers and isolated thunderstorms to Kosrae and Pohnpei later tonight and into Monday. Expecting showers to remain isolated at Majuro tonight, but introduced isolated thunderstorms back into the forecast later tonight as satellite shows some bubbling cumulus to the east of Majuro, where a few cumulus towers start to build and then quickly collapse, suggesting some low- level instability that could spark an isolated thunderstorm later tonight near Majuro. Models show a ITCZ-like pattern rebuilding over the next few days, but it is starting to lack the southeasterly winds associated with a true ITCZ. Regardless, trade convergence and showers should increase across Pohnpei and Majuro later this week, while showers will likely be mainly north of Kosrae until about Thursday, when the pattern starts to fragment into a series of troughs. Altimetry shows combined seas are between 4 and 6 feet, with scatterometer showing gentle to moderate winds across most of the region, Marine conditions are not expected to change much the next several days. && .Western Micronesia... The convergent flow that has been near Palau and Yap Proper has now pulled far enough west that showers are now isolated across both locations. Over by Chuuk Lagoon, a TUTT cell just to the northwest is starting to increase shower and thunderstorm activity to the east of the lagoon, and this should move through the Chuuk Lagoon later tonight. As the trade-wind pattern becomes more active across Micronesia, expect scattered to numerous showers across Chuuk State through the middle of the week. Models show the TUTT weakening over the next few days, but is expected to continue to drift westward. This should start to increase showers across eastern and then western Yap State over the next few days, while showers at Palau will be more episodic, relying more on passing trade-wind troughs to bring in some periods of scattered showers. Yap and Palau buoys indicate seas are around 4 feet, and altimetry shows seas around 4 to 5 ft across the region. Scatterometer data shows winds are gentle to moderate. Seas and winds are expected to change very little over the next few days. && .GUM WATCHES/WARNINGS/ADVISORIES... GU...None. MP...None. Marianas Waters...None. && $$ Marianas: Slagle Micronesia: Schank