364
FXPQ50 PGUM 281909
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
509 AM ChST Fri Aug 29 2025

.Marianas Update...
Convection has decreased across the Marianas this morning, with
partly sunny conditions expected through the morning. A trade-wind
trough, currently east of the waters, is expected to approach the
Marianas this afternoon, bringing scattered showers and isolated
thunderstorms back to the region. The remainder of the forecast
remains unchanged, with an overall wet pattern expected over the
weekend.

&&

.Eastern Micronesia Update...
There were a few small changes for the short term from the previous
forecast. For Pohnpei, cloud cover was increased to cloudy skies with
scattered showers. The POPs (Probability of Precipitation) were
lowered to 30% as most of the convection has pushed west of the
island. Although the risk of thunder has decreased, isolated
thunderstorms do remain a possibility. For Kosrae, also increased
cloud cover to cloudy, however, POPs remain at 40%, with scattered
showers and isolated thunderstorms possible through the day. For
Majuro, convection has decreased across the atoll, with partly
cloudy skies and isolated showers now seen over the area. However,
showers and thunderstorms are approaching from the east, which should
bring scattered showers and isolated thunderstorms back to the atoll
this afternoon. Otherwise, no changes to the forecast.

&&

.Western Micronesia Update...
A monsoon pattern continues across western Micronesia this morning.
Convection has decreased significantly across Yap, but increased
across Palau this morning. Shower coverage was increased to numerous
a bit earlier than expected for Palau, with this wet pattern
continuing into Sunday. For Yap, scattered showers and isolated
thunderstorms look to move back into the area this afternoon. Yap
will also see a wet pattern continuing through the weekend. The
remainder of the forecast remains unchanged.

For Chuuk, a weak circulation with strong convergence is seen over
Chuuk State, bringing numerous showers and isolated thunderstorms to
Weno through the day. Gusty winds and locally heavy showers remain a
possibility through today. The remainder of the forecast is
unchanged, however, shower coverage may need to be increased for a
short time this evening.

&&

.Prev discussion... /issued 612 PM ChST Thu Aug 28 2025/

Marianas Synopsis...
Latest satellite and radar imagery show mostly cloudy skies and
scattered showers over the region this afternoon. Buoy and altimetry
data show combined seas 3 to 5 feet.

Discussion...
An active weather pattern continues across much of Micronesia, which
is influencing the weather across the Marianas. Scattered showers
late this afternoon is expected to persist through the evening, then
the islands may see a relative lull in showers tonight and Friday
morning before an increase in convergence and moisture ahead of a
broad surface trough will trend towards a wetter pattern by Friday
night and through the weekend. The trough would be anchored to a
potential disturbance closer to Yap, so timing and intensity of
showers may be dependent on its development and vary in subsequent
model runs. Similarly, seeing some potential of convectively-driven
gusts to 25 mph with this feature, but awaiting for more model
consensus before including into the forecast at this time.

Marine/Surf...
Gentle to moderate easterly trades become light to moderate
southerlies over the weekend, as a broad surface trough passes
through. Combined seas of 3 to 5 feet are expected to continue over
the next several days, with occasional wind-driven short-term
increases, especially over the weekend. A moderate risk of rip
currents continues along east facing reefs for the next several days.

Eastern Micronesia...
A wet and unsettled pattern continues across much of eastern
Micronesia. Satellite this afternoon shows numerous showers covering
much of the northern and central RMI, nearly all of Kosrae State,
and southern Pohnpei State, becoming more scattered further north near
Pohnpei itself. The Intertropical Convergence Zone (ITCZ) remains the
dominant feature across the region, extending westward from across
the Date Line near 9N180, passing over the Marshall Islands just
north of Kwajalein, to end near a weak circulation in eastern Chuuk
State. Most of the showers and isolated thunderstorms are seen along
and south of the ITCZ, with another area of strong convergence seen
over southern Pohnpei State extending westward into southern Chuuk
State. Models show an increase in showers over Pohnpei tonight as the
ITCZ lifts northward, with showers becoming numerous around midnight.
At the same time, Kosrae and Majuro should see a gradual decrease in
showers through the overnight hours as the strongest convergence
shifts north of the area. Some higher gusts are possible near heavier
showers, with this morning`s scatterometry indicating 20-knot gusts
near Kosrae, with some 25-knot gusts seen in the convective bands
further southeast, south of Pohnpei. After tonight, scattered showers
will gradually diminish in coverage over the next few days across
Pohnpei and Kosrae, while Majuro can expect an increase by the
weekend as a fragment of the ITCZ reasserts itself nearby, bringing
numerous heavier showers across the area from Friday night through
Saturday night. This will be followed by a relative lull in showers
through early next week as the ITCZ diminishes.

Higher winds and gusts are leading to choppier seas near Kosrae, with
buoys and altimetry data indicating 5 to 6 foot seas there, with
slightly more relaxed seas of 3 to 5 feet near Pohnpei, and around 4
to 6 foot seas for Majuro. Overall sea conditions are expected to
remain benign as a primary east to southeast trade swell dominates.
Gentle to moderate winds will persist across the region outside of
heavier showers through the forecast period. Seas will relax by a
foot or two across the region for the latter half of the weekend
through early next week, as the trade swell relaxes.

Western Micronesia...
Latest satellite imagery and surface analysis still shows that the
monsoon trough is north of Yap, but there appears to be a weak,
elongated circulation east-northeast of Yap near 11N143E, between
the monsoon trough and the surface trough southwest of the Marianas
and near Chuuk State. The proximity of the weak circulation near Yap
is causing winds to become more variable in direction across Yap
State, while westerly winds continue across Palau, still around 10-15
kt with patches of 20-25 kt within showers, based on today`s
scatterometry and AMSR2 ocean surface wind data. Over by Chuuk, a
weak circulation is still south of Chuuk, connected to the broad
surface trough extending east-northeast across eastern Micronesia,
producing scattered to numerous locally heavy showers across Chuuk
and Pohnpei States, and to the north of Kosrae and west of Majuro.

As the surface trough passes through Chuuk tonight and Friday,
numerous, locally heavy and gusty showers are expected across the
State, with showers then decreasing in intensity and coverage Friday
night and through the weekend as the trough shifts west-northwest
towards the Marianas, Yap, and Palau. for Palau and Yap, convection
is still cycling through periodic flare ups, with scattered showers
currently just east of Yap, near the weak circulation, and just
southwest of Palau along convergent southwest flow. Over the
weekend, the trough near Chuuk will trek WNW, bringing increased
moisture to Yap and Palau. Ensemble model guidance still suggests 3-5
inches of rainfall are possible Sunday, led by a still aggressive
GFS. The GFS is still showing winds increasing around Sunday, but the
most recent runs of the deterministic and ensemble have started to
back off slightly on peak winds and are favoring a more northern
shift of stronger winds just north of Palau and Yap. The ECMWF is
still much less aggressive with winds compared to the GFS but the
most recent run of the deterministic and ensemble have trended
slightly higher and also favor the stronger winds just north of Palau
and Yap. It appears the two global models are starting to come to a
consensus, so the most likely scenario for Palau and Yap looks to be
periods of heavy showers and gusty winds, that may lead to choppy
seas but seas hand surf are still expected to remain below hazardous
levels of 10 feet and 9 feet, respectively. Seas will hover between 3
and 5 ft the next several days at Chuuk, but may spike a couple of
feet higher tonight and Friday due to gusts, and between 4 and 7 ft
for Yap and Palau. Highest seas will be found within the stronger
westerly flow south of Palau.

&&

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

$$

Marianas/East Micronesia/West Micronesia Updates: Kleeschulte
Marianas: Cruz
East Micronesia: DeCou
West Micronesia: Schank