315
FXPQ50 PGUM 110810
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
610 PM ChST Sat Oct 11 2025

.Marianas Synopsis...
Satellite and radar this afternoon reveal isolated showers and partly
cloudy skies across the islands, with fairly uniform conditions
upstream. Buoy and altimetry data indicate combined seas of 4 to 6
feet.

&&

.Discussion...
Similarly quiet conditions will continue across the Marianas through
the rest of the weekend, with a build-up of showers early next week
as a broad trough and possible weak disturbance shift northwest into
the area from over Chuuk State. The more aggressive model solutions
depict a tropical depression forming just west of the Marianas around
Wednesday, while most models maintain the disturbance as a robust
open surface trough. Overall, this will bring a wetter pattern from
around Monday night through at least Wednesday night, with showers
becoming numerous at times midweek. Showers may become locally heavy
at times and provide some stronger gusts, with a peak around
Wednesday and Wednesday night. Quieter conditions will resume by the
end of the week as a low-level ridge briefly sets up nearby.

&&

.Marine...
Combined seas will remain at around 4 to 6 feet through the period,
comprised of a long-period north swell and a secondary trade swell.
Winds will be gentle to moderate out of the northeast to east through
the weekend, becoming moderate to fresh at times early next week as
a weak disturbance lifts northwest through the area. Seas may
increase by a foot or so around Tuesday with an expected increase in
winds and wind waves. The long-period north swell, emanating from
distant tropical systems, is generating elevated surf along north
facing reefs, and wrapping around the islands to increase surf along
east and west facing reefs as well. There will be a moderate risk of
rip currents along north, east, and west facing reefs of the Marianas
through at least Sunday night. Exercise caution, as narrow reefs and
channels may see strong rip currents develop. North swell and
associated surf will gradually diminish through the next few days.

&&

.Eastern Micronesia...
A broad Tropical Upper-Tropospheric Trough (TUTT) cell persists to
the south-southwest of Wake Island and north of eastern Micronesia,
and is helping to enhance convection across the region. Satellite
reveals scattered showers over Majuro waters, becoming numerous just
further east extending beyond the Date Line, within a fragmented
Intertropical Convergence Zone (ITCZ). Widespread cloud cover and
scattered to numerous showers are seen over Kosrae and near Pohnpei,
within a robust southwest-northeast oriented trough. A series of
outflow boundaries is pushing westward toward Pohnpei waters from
prior deep convection within the trough. Scatterometry this afternoon
reveals a fairly modest gentle to moderate wind field across the
region, with the exception of strong, near-gale force gusts seen near
Kosrae associated with deep convection in the area. The broader
trough will continue to push westward, maintaining a wet pattern for
Pohnpei and Kosrae through the remainder of the weekend, continuing
into early next week for Pohnpei. Majuro will continue to see
scattered showers nearby this evening with an expected decrease
overnight as the ITCZ fragment lifts further north. Majuro will see a
resurgence in showers early next week as the ITCZ redevelops over
the area in earnest, with showers possibly becoming numerous at times
around Tuesday and Wednesday.

Benign marine conditions continue, with buoys and altimetry
indicating combined seas around 3 to 5 feet across the region,
comprised of mixed swell mainly from the north-northeast and south-
southeast. Seas will increase by a foot or two late Sunday through
early next week as a long-period north swell arrives, generated by
distant tropical systems. Marine and surf hazards are not expected at
this time, but the incoming swell will be closely monitored as surf
may approach hazardous levels of 9 feet along north-facing reefs of
Pohnpei and Kosrae.

&&

.Western Micronesia...
A broad surface trough extends across Chuuk State, generating
scattered showers across the area while thunderstorms have been very
isolated and mainly south Chuuk Lagoon and surrounding islands, found
mainly between 2N and 4N. Winds look to be light to gentle across
the trough with easterly winds around Chuuk Lagoon, located north of
the trough axis, but shifting towards the west, south of 6N, south
of the trough axis. Over by Palau and Yap, winds here are still
fairly light and variable across the region, with drier air settled
over the islands. The 00Z RAOB sounding from this morning showed
precipitable water (PW) values around 1.8 to 1.9 inches, which is on
the drier side for the area and helping to explain the lack of
showers. The latest loop of the Blended TPW satellite imagery shows
this pocket of dry air extending across Yap State and is shifting
westward, suggesting Palau and Yap will remain in this pocket of
drier air tonight and through Sunday, helping to limit shower
development, even if light winds and partly cloudy skies create
conditions favorable for island-effect showers over Palau during peak
heating in the late morning and early afternoon hours.

For Chuuk, model guidance supports this surface trough slowly lifting
northwest through Chuuk state and the towards Marianas over the next
few days, this will keep a wetter pattern in place over Chuuk. The
peak of the showers is expected to occur around Monday as the trough
axis moves across, with the potential for some gusts around 25 kt
(~30 mph) due to showers. As this trough moves off to the northwest,
winds and showers are expected to decrease Wednesday, before the next
series of troughs move into the area from near Pohnpei, helping to
keep periods of scattered showers in the forecast for later in the
week. For Palau and Yap, as the surface trough in Chuuk State lifts
northwest, there may be alight influx of moisture at Palau and Yap,
through the beginning of the upcoming week, but with models showing
a lack of major features, and winds remaining fairly light to gentle
across the region, any showers will likely be episodic and related
to weak convergence or island heating during the daytime hours.

Combined seas of 3 to 5 feet are expected across the region through
Sunday, before increasing slightly about a foot near Chuuk Monday as
a northerly swell emanating from a distant tropical and mid-latitude
systems well north of the region, makes its way across Micronesia,
and winds waves increase due to a passing surface trough. Northerly
swells will replace the southwest swell that was dominating much of
Palau and Yap waters the last few days, which 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 across Palau, Yap, and Chuuk by
these swells as models show the swell peaking at a height of 5 feet
and period of 12-14 seconds Monday, keeping surf along north facing
reefs below hazardous levels of 9 feet.

&&

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

$$

Marianas/East Micronesia: DeCou
West Micronesia: Schank