609
FXPQ50 PGUM 090823
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
623 PM ChST Thu Oct 9 2025

.Marianas Synopsis...
Satellite imagery shows partly cloudy skies, while radar imagery
shows isolated showers over the Marianas. Altimetry shows 3 to 4 feet
combined seas, and buoy data confirms these sea heights.

&&

.Discussion...
A slow moving broad surface trough will be moving into the region
tonight from the east, coupling with an upper-level low over the
Marianas, producing a recipe for scattered showers and isolated
thunderstorms over the area. The upper-level low is moving a bit
faster than the trough, though, so this upper-level support will
eventually out-run the trough. This will result in less shower and
thunder coverage the next few days. The trough is expected to be out
of the coastal waters and into the Philippine Sea around Friday
night. Once this system passes, a return to a trade-wind pattern is
expected.

Model guidance shows in the longer term, that an east-west trough in
Yap State may produce a tropical disturbance. While models suggest it
will mostly remain in Yap State, this system may cause a convergence
zone over the Marianas and produce some showers around the beginning
of next week. However, at this time impacts are anticipated to be
minimal.

&&

.Marine...
Winds are expected to be light to gentle for the next few days, and
will become moderate by Sunday. Combined seas of 3 to 5 feet will
persist through Friday, to then build to 5 to 7 feet thereafter, as a
long-period north swell moves through the region from the distant
Typhoon Halong.

For the surf, there is a moderate risk of rip currents along east
facing reefs, with a low risk along all other reefs expected through
Friday. Then, the swell emanating from distant Typhoon Halong is
anticipated to arrive. This swell is expected to  increase surf
along north facing reefs, and increase the risk of rip currents to
moderate by Saturday. There will also be a moderate risk of lightning
the next few days.


&&

.Tropical Systems...
Tropical Storm Nakri (29W) is centered near 24N135E well west of
Iwo-To. This system is moving north-northwest at 14 mph, with maximum
sustained winds of 45 mph. This system is expected to continue to
move in this general direction toward the Ryukyu Islands, followed by
a slight acceleration in forward speed through Friday, to then turn
northeast toward Kyushu, Japan. This system will maintain this
intensity overnight, to then gradually intensify as it exits the WFO
Guam Area of Responsiblity (AOR). As such, this system is not
expected to have any direct impact to any islands in our region.

&&

.Eastern Micronesia...
An east-west oriented trough extends across the central Marshall
Islands from across the Date Line, passing over Majuro and to the
south of Kwajalein. Satellite this afternoon showed scattered
showers across the area, including over Majuro coastal waters, with
most of the showers just east of the RMI along the trough axis.
Conditions are fairly quiet across the rest of eastern Micronesia,
with isolated to scattered showers seen near Pohnpei and just
isolated showers around Kosrae. Slightly better surface convergence
near Pohnpei will maintain better shower chances there overnight. The
east-west trough centered near Majuro will gradually shift west
through the next few days, increasing showers for Kosrae and Pohnpei
during the weekend, mainly from Saturday night onward. Early next
week, the Intertropical Convergence Zone (ITCZ) looks to become
active across the RMI and shift westward, bringing more substantial
shower chances across the region during the first half of next week.

Buoy and altimetry data show combined seas of around 2 to 4 feet
near Pohnpei and Kosrae and 3 to 5 feet near Majuro. The Coastal
Flood Advisory for Majuro was extended until Friday at 3 PM ChST, as
observed coastal water levels have been running about half a foot
higher than predicted, indicating a continued possibility for minor
flooding during times of high tide. Late this weekend, a long-period
elevated north swell looks to move into the region, emanating from
distant Typhoon Halong and Tropical Storm Nakri. This will increase
combined seas by 1 or 2 feet, but no marine or coastal hazards are
expected at this time. The expected north swell will be closely
monitored in the forecast over the next few days. Winds are expected
to remain light to gentle across the region through the forecast
period.


&&

.Western Micronesia...
A southwesterly monsoon clashing with a trade-wind convergence zone
will continue to bring unsettled weather to Palau and Yap through
Friday. These on-and-off showers and some thunderstorms will bring
moderate to occasionally strong winds to Palau tonight, before
slowing significantly over the next few days as winds diminish across
much of western Micronesia, as a ridge extending across the Marianas
to the northeast dips down slightly through Thursday. After a brief
period of drier weather at Palau and Yap during the weekend, an east-
west oriented trough is expected to form, extending from a potential
tropical disturbance in eastern Yap State to then follow said
trough`s axis on its way west, with little significant impact
expected to the region at this time. Low-end scattered showers are
expected for much of the forecast period at Chuuk, as gentle to
moderate trades continue and bring a period of drier conditions
during the weekend, followed by increasing showers next week.

Combined seas of 3 to 5 feet are expected across the region through
the weekend, before increasing slightly near Chuuk as a northerly
swell emanating from a distant Typhoon Halong near Japan, makes its
way across the area. Pulses of southwest swell are expected to make
their way across Palau and Yap the next few days, before various
northerly swells overtake the monsoon swell during the weekend.
This will cause surf to build along north-facing reefs, while
diminishing along south and west reefs of Palau and Yap. At this
time, no significant marine and/or surf impacts are expected by these
swells.

&&

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

$$

Marianas: Bowsher
East Micronesia: DeCou
West Micronesia/Tropical: Montvila