Area Forecast Discussion
Issued by NWS Tiyan, Guam
Issued by NWS Tiyan, Guam
459 FXPQ50 PGUM 300701 AFDGUM Area Forecast Discussion National Weather Service Tiyan GU 501 PM ChST Sun Jun 30 2024 .Marianas Synopsis... Satellite imagery is showing increasing clouds and showers this afternoon. A few lightning strikes were observed west of Guam. Latest altimetry and Ritidian buoy data are indicating seas of 3 to 5 feet. && .Discussion... A disturbance to the southeast of the Marianas will push across the region through tomorrow. Latest CIMSS MIMIC Precipitable Water is showing a over 2 inch values approaching the CNMI and over 2.5 inches approaching Guam. Have scattered showers for Tinian and Saipan through tonight and for Guam and Rota through tomorrow. While the upper-level support for thunderstorms has diminished and the model Galvez-Davison Index (instability) is marginal, have included a slight chance for thunderstorms as there have been a few strikes observed earlier to the west of Guam. For the rest of the period, multiple disturbances will pass near to south of the Marianas. Expect upticks in clouds and showers, especially for Guam and Rota, where moisture will be deeper and convergent flow will be more prevalent. && .Marine/Surf... Gentle to moderate trade winds and combined seas of 3 to 5 feet will continue this week. Some gusty winds and choppy seas are possible at times through the week near heavier showers and thunderstorms, especially over Guam and Rota waters, as a couple of disturbances pass near to south of the Marianas. A moderate risk of rip currents will continue along east facing reefs, with a low risk along all other reefs. Little change in surf and rip risk expected through the week. && .Eastern Micronesia and Chuuk... Developing ITCZ is producing spotty showers and is expected to remain spotty as the models show the ITCZ remaining weak with the TUTT moving out. Thus, lowered the probability of precipitation (POP) slightly from the previous forecast. Tuesday, models indicate a localized increase in showers along the leading edge of the ITCZ near Pohnpei around Monday night, then to Chuuk Tuesday, then fizzling out before it reaches Yap. The heavier showers look to pass north of Pohnpei and Chuuk but will bring scattered showers for them Monday night Tuesday. An increase in shower potential is expected late week for Majuro and possibly for Kosrae as convergent tradewinds develop over by the Marshalls and move across the region. Seas of 4 to 6 feet were observed by altimetry near Majuro and Kosrae. Not much change is expected for marine conditions. Gentle to moderate trades are expected at times. && .Western Micronesia for Palau and Yap... The near-equatorial trough continues to produce some showers nearby Koror`s waters. Latest model run shows that heavier showers are expected to develop west of Koror near the disturbance this evening, and we should also see convective activity increasing along the near- equatorial trough to bring scattered showers tonight for Koror and Yap. Scattered showers are expected for tomorrow also, but should slowly trend down to partly cloudy with isolated showers some time tomorrow. After a brief lull, incoming showers from the east are expected to cross both Koror and Yap around mid-week. Seas of 3 to 5 feet were observed by altimetry near Koror and Yap`s waters, and buoys reported around 4 feet. Not much change is expected for marine conditions. Mostly gentle trades are expected, becoming moderate at times. && .GUM WATCHES/WARNINGS/ADVISORIES... GU...None. MP...None. Marianas Waters...None. && $$ Marianas: Slagle Micronesia: Hong