772
FXPQ50 PGUM 081945
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
545 AM ChST Tue Dec 9 2025

.Marianas Update...
The forecast has not changed much overnight. Gentle to moderate
northeasterlies and dry weather prevail across the Marianas, with
buoys reporting seas around 5 to 7 feet. A shear line to the north is
expected to fragment and shift southward, bringing breezy conditions
and low-end showers to the Marianas. Scattered showers were kept in
the forecast for tonight, but newer model data is starting to delay
the start of scattered showers to Wednesday, matching the start of
breezy conditions. Once daylight makes visible satellite imagery
available, it will be easier to track the movement of the shear line
and determine if newer model data is correct with the timing and
movement of the the shear line. Once these fragments dissipate or
get carried downstream, drier diffusive flow will return to the
Marianas.

The Marianas is beginning its transition into dry season, which
usually sees an increase in shear lines, especially during January
and February, as strong cold front push off Japan and decay in the
tropics. Dry season is also the time when drought is more likely
develop in our region and increase the risk of fires to spread
rapidly, especially during breezy conditions, if control of a fire
is lost. This is something to keep in mind over the next few weeks
and months.

Combined seas of 6 to 8 feet are expected to occasionally go up a
foot due to increased wind waves generated by shear line fragments.
A moderate risk of rip currents is expected along north and east
facing reefs of the Marianas for at least the next few days, with the
potential that high surf of 9 feet will build once again along north
facing reefs later this week if the north-northeast swell builds in
response to stronger winds along the shear line.

&&

.Eastern Micronesia Update...
Satellite this morning shows a dry trade-wind pattern across
Pohnpei, Kosrae, and Majuro. Southwest of Pohnpei and Kosrae, a band
of scattered showers and isolated thunderstorms is seen, focused
along the NET which extends east-southeast into the region from over
Chuuk State, and supported by a broad upper-level trough, extending
from a low centered northeast of the RMI. models show this upper-
level supporting helping to increase showers slightly at Majuro late
this afternoon through Wednesday as a weak trough moves in from
across the Date Line, but otherwise dry weather will be the main
pattern across the region for the rest of the week. Models still
depict a more robust trough moving into the region this coming
weekend, increasing showers mainly over the RMI. The upper-level low
supporting the showers and thunderstorms southwest of Pohnpei and
Kosrae looks to gradually shift east and exit the region by the end
of the week.

Buoys and altimetry data indicate combined seas of around 7 to 8
feet near Pohnpei and Majuro, and 6 to 7 feet near Kosrae. Buoy data
and model guidance continue to support a decreasing trend in sea
heights as the north swell and primary trade swell diminish through
Friday. Model data is indicating another pulse of northerly swell
will move through this weekend which may produce a brief period of
surf up to 9 feet along north facing reefs. Winds look to stay gentle
to moderate throughout the rest of the week.

&&

.Western Micronesia Update...
A dry trade regime continues across the main forecast points of
Palau, Yap and Chuuk this morning. Pockets of scattered showers and
isolated thunderstorms continue to develop along a segment of the
Near-Equatorial Trough (NET), but remain well southeast of Chuuk
Lagoon, and east to southeast of Palau and Yap Proper. Models still
indicate the potential for scattered showers (chance of showers
around 30 percent) at Yap and Palau tonight as troughing and
convergence increase along the western periphery of the NET just
south of Koror. Scattered showers look to continue over Palau through
midweek before the NET axis retreats further south in the latter
half of the week. Trade-wind troughs propagating westward through the
region north of the NET will occasionally interrupt the dry trade
regime across the region, with another period of scattered showers
or two expected this weekend.

Altimetry data from this morning indicates combined seas around 4 to
6 feet near Palau and Yap, and 5 to 7 feet around Chuuk. The higher
seas near Chuuk are likely associated with the lingering north swell,
combined with a slowly decreasing but still elevated trade swell.
The marine forecast remains fairly steady through the rest of the
week as the northeast trade swell remains dominant, with seas
diminishing slightly for Palau and Chuuk before coming back up by a
foot or so this weekend. Winds will be light to moderate for Palau
and Chuuk throughout the forecast period, staying mostly moderate for
Yap.

&&

.Prev discussion... /issued 703 PM ChST Mon Dec 8 2025/

Marianas Synopsis...
Gentle to moderate northeasterlies prevail across the region. Doppler
radar indicates light passing showers in the Guam and Rota waters.
Buoys show seas are about 5 to 7 feet.

Discussion...
As a quieter trade-wind regime continues through Tuesday, descending
shearline fragments from the north are expected to bring breezy
conditions with low-end scattered showers around midweek. Once these
fragments dissipate or get carried downstream, drier diffusive flow
will return to the Marianas.

Marine...
Multiple northerly swells have weakened enough to allow surf to drop
below hazardous levels along north facing reefs of the Marianas,
which in turn, also allows the rip current risk to drop to moderate
along said reefs. As such, the High Surf Advisory and High Rip
Current Risk Statement were allowed to expire earlier this afternoon.
Combined seas of 6 to 7 feet are expected to occasionally go up a
foot through Wednesday night, to then potentially increase another
few feet as shearline fragments shift southward into the Marianas. A
moderate risk of rip currents is expected along north and east facing
reefs of the Marianas for at least the next few days, before surf
becomes hazardous once again along north facing reefs in the second
half of the week.

Eastern Micronesia...
Satellite this evening shows a mostly dry trade-wind pattern across
the region, with isolated showers and partly cloudy skies seen over
Pohnpei, Kosrae, and Majuro. Southwest of Pohnpei and Kosrae, a band
of scattered showers and isolated thunderstorms is seen, focused
along the NET which extends east-southeast into the region from over
Chuuk State, and supported by a broad upper-level low centered
northeast of the RMI. Showers will increase slightly near Majuro
around Tuesday night and Wednesday as a weak trough moves in from
across the Date Line, but otherwise conditions look to remain mostly
dry throughout the week. Models depict a more robust trough moving
into the region this coming weekend, increasing showers mainly over
the RMI. The upper-level low supporting the showers and
thunderstorms southwest of Pohnpei and Kosrae looks to gradually
shift east and exit the region by the end of the week.

Buoys and altimetry data indicate combined seas of around 8 to 9 feet
near Pohnpei, Kosrae, and Majuro. Latest buoy data and model guidance
depict a decreasing trend as north swell and the background trade
swell diminish throughout the week, and the High Surf Advisory has
been cancelled for Pohnpei, Kosrae, and Majuro. Likewise, the Small
Craft Advisory was cancelled for Pohnpei. Winds look to stay gentle
to moderate throughout the week.

Western Micronesia...
A fairly dry trade regime continues across much of western
Micronesia, with only isolated showers seen near Chuuk, Yap, and
Koror coastal waters this afternoon. A little further south of these
forecast points, Himawari visible satellite imagery shows scattered
showers extending across eastern Yap State and western Chuuk State,
along a segment of the Near-Equatorial Trough (NET), but remaining
southwest to south of Weno coastal waters, and east to southeast of
Palau and Yap Proper. Models depict the NET meandering southward over
the next day or so, with only isolated showers expected until around
Tuesday night, where Probability of Precipitation (PoP) was
increased to 30 percent for Yap and Palau as troughing and
convergence increase along the western periphery of the NET just
south of Koror. Scattered showers look to continue over Palau through
midweek before the NET axis retreats further south in the latter
half of the week. Trade-wind troughs propagating westward through
the region north of the NET will occasionally interrupt the dry
trade regime, with another period of scattered showers or two
expected this weekend.

Altimetry data from this morning indicates combined seas around 4 to
6 feet near Palau and Yap, increasing up to 7 to 9 feet just west of
Chuuk. The higher seas near Chuuk are likely associated with the
pulse of long-period north swell that is passing through the region,
combined with the elevated trade swell, but these swells will
continue to subside through the next few days allowing surf to fall
below hazardous levels of 9 feet, and the High Surf Advisory for
north-facing reefs of Chuuk was allowed to expire at 5 PM ChST. The
marine forecast remains fairly steady through the rest of the week
as the northeast trade swell remains dominant, with seas diminishing
slightly for Palau and Chuuk before coming back up by a foot or so
this weekend. Winds will be light to moderate for Palau and Chuuk
throughout the forecast period, staying mostly moderate for Yap.

&&

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

$$


Marianas/East and West Micronesia Update: Schank
Marianas: Montvila
East/West Micronesia: DeCou