281
FXPQ50 PGUM 210755
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
555 PM ChST Thu Aug 21 2025

.Marianas Synopsis...
Satellite shows scattered showers across the region, with denser
cloud cover over Guam and Rota this afternoon. Radar imagery shows
the deeper convection earlier this afternoon trending down in
intensity and coverage. However, locally heavy showers are still
over southern Guam waters and farther east of the region. Buoys show
steady seas between 3 and 4 feet.

&&

.Discussion...
A broad trough extends from an active pattern in western Micronesia.
Overall convergence across the region has increased, with scattered
showers expected through least Friday afternoon. Locally heavy
showers are still possible for Guam and Rota through tonight. Then a
subtle trough may move through Saturday, bringing another period of
scattered showers. Models are showing a bit more organized convection
early next week. This is largely dependent on another tropical
disturbance developing well to the south, so some uncertainty exists,
but more can be gleaned from subsequent model runs.

&&

.Marine/Surf...
Locally heavy showers with gusts to 20 kt are possible for Guam and
Rota tonight. Otherwise, combined seas of 3 to 4 feet and light to
gentle winds are expected over the next few days, increasing to 3 to
5 foot seas and gentle to moderate trades next week. There will be a
moderate risk of rip currents along east facing reefs through
tonight. On Friday, the rip risk for east facing reefs drops to low
and rip risk is expected to remain low for all reefs through the
weekend.

&&

.Eastern Micronesia...
The main item of interest is a surface trough that stretches from
just northeast of Kosrae to between Kwajalein and Majuro. Another
trough in the trades is located from east of Majuro at 176E between
6N and 12N. Extensive cloud cover with scattered showers will
continue to accompany these features as they head west the next
several days, with a few thunderstorms mixed in from time to time as
well.

As for sea conditions, mainly light to gentle winds may increase
briefly to moderate at times, with seas of 3 to 6 feet expected.

&&

.Western Micronesia...
A broad trade-wind trough extends southwest into Yap State from just
east of the Marianas, passing over Ifalik and Eauripik before curving
to the south of Ngulu. Along the forward edge of this trough,
satellite reveals a band of scattered to numerous showers and
isolated thunderstorms extending south-southwest from the Marianas
and across western Yap State, building westward over the Republic of
Palau this afternoon. Scatterometry reveals a few higher gusts of 20
to 25 knots associated with this convection, with otherwise mostly
gentle to moderate trades throughout the region. To the east on the
backside of the trough, satellite shows scattered showers building
over Chuuk, associated with broad trade-wind convergence.

The trade-wind trough will continue to push west and maintain
numerous showers for Palau and Yap overnight. Model consensus
continues to show the development of a weak circulation in the area
along the southern edge of this trough, late overnight through
Friday, then gradually pushing northwest across Palau through
Saturday. ECMWF is being particularly aggressive in depicting this
feature along with the extension of a monsoon trough into the region.
These features will maintain at least scattered shower coverage near
Palau and Yap through early next week. Winds will become light and
variable at times through Monday, looking to gradually shift westerly
across Palau early next week. Chuuk can expect a relatively quieter
forecast period, with a series of weaker troughs crossing the area
late Friday through the weekend, bringing periods of scattered
showers and isolated thunderstorms.

Altimetry data shows benign seas across the region, with combined
seas of around 2 to 3 feet near Palau, 2 to 4 feet near Yap, and
around 3 to 4 feet near Chuuk. Seas look to increase by a foot or two
early next week mainly across Palau waters, as a south to southwest
swell sets up in response to a developing monsoon-like pattern.
However, marine hazards are not expected at this time.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...None.
MP...None.
Marianas Waters...None.
&&

$$

Marianas: Cruz
East Micronesia: Doll
West Micronesia: DeCou