386
FXPQ50 PGUM 152051
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
651 AM ChST Tue Dec 16 2025

.Marianas Update...
The Marianas are currently in the lull after the shear line. A weak
disturbance will increase showers to scattered tonight through
Wednesday night. Thursday and Friday will return to isolated before
the next shear line descends from the north. All this was captured
well by the inherited forecast so no changes were needed.

&&

.Marine...
Seas will be on a slow decline, so the risk of rip currents will
gradually fall. This will make the risk, which is currently high,
become moderate this evening. This will likely remain true until the
weekend with the approach of the new shear line.

&&

.Fire weather...
The past shear line brought enough rain to give us a respite from the
advance of the KBDI. It is starting to increase again though, and
will likely recover all the ground it lost in the next few days. It
remains to be seen if the next shear line will impose another cost
upon it. For the next week or two fire weather will remain more or
less in line because of the time that rain has bought for us.

&&

.Eastern Micronesia Update...
A few showers have started developing recently near Pohnpei. So while
I knocked the PoP`s down 10 percent, I did retain scattered showers.
That was the only change for Eastern Micronesia. Kosrae and Majuro
should be rather dry today, so isolated fit well. Maintained the High
Surf Advisory for Kosrae along east reefs.

&&

.Western Micronesia Update...
Maintained the Small Craft Advisory for Yap. Originally made no
changes for Western Micronesia, with scattered showers for Koror
Palau and Chuuk, and isolated showers for Yap. The showers near Chuuk
started really filling in now, so the oncoming forecaster has gone
ahead and updated for numerous. With the way it`s filling in, that`s
a good call, Chuuk is likely to be the wettest of all the forecast
points today.

&&

.Prev discussion... /issued 614 PM ChST Mon Dec 15 2025/

Marianas Synopsis...
Moderate to fresh northeasterlies prevail across the region.
Satellite imagery and Doppler radar indicate shallow, quick-passing
showers in Guam and Rota waters. Buoys show seas are 7 to 9 feet.

Discussion...
A brief period of drier conditions is expected across the region
through Tuesday, followed by the arrival of a minor mid-to-upper-
level enhanced surface trough that is likely to bring breezy
conditions and low-end scattered showers around midweek. After, a
return to a seasonally drier cycle, followed by another shearline
dipping down and bringing another period of widespread cloud cover,
higher shower coverage and elevated winds through the weekend.

Marine...
Trade swell and localized wind waves induced by a passing shearline
have weakened enough to allow seas to fall below levels hazardous to
small craft. As such, the Small Craft Advisory was allowed to expire
earlier this afternoon. Even so, seas are expected to remain choppy
as said trade swell and secondary northerly swell continue to mix in,
keeping seas elevated for much of the week. As another shearline
makes its way across the region, and another significant pulse in
northerly swell crosses the waters, a Small Craft Advisory may be re-
issued by the weekend. Combined seas of 6 to 8 feet are likely to
persist through Tuesday night, before increasing briefly around
midweek and then increase once again by the weekend as the
aforementioned northerly pulse and higher trade swell make their way
across the region. A high risk of rip currents is expected along east
facing reefs of the Marianas through at least late Tuesday afternoon,
before becoming moderate thereafter, while a moderate risk of rip
currents is expected to continue along north facing reefs for the
next several days.

Eastern Micronesia...
The Intertropical Convergence Zone (ITCZ) extends into the southeast
corner of the region, leading into a broad trough that is spreading
showers southward across northwest Kiribati. Fairly quiet conditions
exists across the main forecast locations this evening. Increasing
convergence to the north and northeast of a weak Near-Equatorial
Trough (NET) disturbance is expected to produce a flare up in
convection across southern Pohnpei State, with scattered showers and
isolated thunderstorms building into Pohnpei coastal waters around
midnight. Afterwards, this area of enhanced convergence looks to
fragment into a few troughs as it moves westward into Chuuk State.
Starting around midweek the ITCZ begins to build across the region,
bringing more unsettled weather near and south of Majuro and
stretches westward into Kosrae late week.

Altimetry and buoy data show combined seas of 5 to 8 feet, with the
Pohnpei buoy showing an increase in longer-period northerly swell
to 3 to 4 feet. Overall, the combination of east to northeast trade
swell and longer-period north swell are elevating surf along north-
and east-facing reefs. Decided to issue a High Surf Advisory for
east-facing reefs of Kosrae due to their lower high surf threshold
of 8 feet. This pulse of north swell slightly subsides around
midweek, however, trade swell is expected to increase, maintaining
the hazardous surf along east reefs through late week.

Western Micronesia...
Latest satellite data shows a dry pattern over Yap, Palau and Chuuk,
with convection associated with the Near-Equatorial Trough (NET)
seen to the south of Yap Proper to southwest of Weno. Altimetry shows
seas between 7 and 9 feet to the east of Yap, with seas up to 11
feet farther north. Seas are between 4 and 7 feet at Palau and Chuuk.

The NET remains the primary player across western Micronesia. As the
NET drifts west, convection looks to remain to the southeast of
Palau to southwest of Weno. The dry pattern currently seen across the
region looks to continue at Weno tonight. Convection looks to
increase Tuesday morning as the eastern end of the NET drifts north
and a weak trade-wind trough moves in to interact with the NET. A dry
pattern is then expected to return to Chuuk Wednesday night and
continue into the weekend.

For Palau, showers look to increase as the NET approaches Tuesday
morning, with scattered showers and isolated thunderstorms moving in
early in the morning. Showers look to gradually increase through
Tuesday night, with numerous showers and isolated thunderstorms
moving into the Republic by Wednesday morning. Not expecting locally
heavy rainfall at this time due to heavier showers remaining south,
though this does remain a possibility. An overall unsettled pattern
then looks to continue across Palau into the weekend.

For Yap, dry conditions look to continue at Yap Proper through
midweek as the NET remains south of the island. Around Thursday,
convection associated with the NET looks to drift far enough north to
bring increased showers and a risk of thunderstorms to the island
through Friday. As the NET continues to drift west, a dry pattern
will return to Yap for the weekend.

For the marine forecast, combined seas look to increase over the next
couple of days across Yap and Palau. Yap is expected to see the
biggest change as north swell, a building trade swell and wind waves
push seas up to around 10 feet. Along with the seas, moderate to
fresh winds wind frequent strong gusts are also expected to move into
the region. Therefore, a Small Craft Advisory was issued for Yap
beginning 5 am Tuesday morning and continuing through Wednesday
afternoon. Seas and wind are expected to subside by Wednesday
afternoon. For Palau, seas are expected to reach as high as 8 feet
before beginning to subside near the end of the week. Chuuk will see
building seas later in the week into the weekend. Winds look to
remain moderate to fresh through the week at Palau, with gentle to
moderate winds at Chuuk becoming moderate to fresh Thursday.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...High Rip Current Risk until 4 PM ChST this afternoon for GUZ001.

MP...High Rip Current Risk until 4 PM ChST this afternoon for MPZ001>003.

Marianas Waters...None.
&&

$$


Marianas/East and West Micronesia Update: Stanko
Marianas: Montvila
East Micronesia: Cruz
West Micronesia: Kleeschulte