149
FXPQ50 PGUM 281951
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
551 AM ChST Sat Nov 29 2025

.Marianas Update...
Winds have increased a little and are now expected to become breezy
today at Tinian and Saipan and Sunday at Guam and Rota. This was
pretty much expected already yesterday afternoon, so no substantial
changes were needed. Scattered to numerous showers will reign the
next few days as a broad trough moves through, centered to the south.

&&

.Marine...
Seas are about 5 to 7 feet on the buoys this morning, but are
expected to swell to 7 to 9 feet as a north swell comes down from a
large storm that moved off Japan earlier this week. A high risk of
rip currents will be possible for a time early this week.

&&

.Eastern Micronesia Update...
Only weak features in Eastern Micronesia at this time. A couple of
weak trade-wind troughs and a weak ITCZ (Inter Tropical Convergence,
leading to mostly isolated with a couple of low-end scattered shower
periods. However, around Sunday, some models have the ITCZ bouncing
back and getting beefed up after Sunday. I left the forecast
unchanged, but am going to take the under on that bet at this time.
The heavier showers begin Sunday night at Pohnpei, Monday at Kosrae,
but possibly tonight at Majuro.

&&

.Western Micronesia Update...
The main feature affecting Western Micronesia is a weak circulation
in the Near-Equatorial Trough. This trough does not have much in the
way of deep convection, one area south of Yap and east of Palau, and
another area south of Chuuk. These are likely to be changeable, both
in area and time, so we will keep an eye on them. The inherited
forecast agreed well with satellite this morning, so no changes were
needed.

&&

.Prev discussion... /issued 611 PM ChST Fri Nov 28 2025/

Marianas Synopsis...
Gentle to moderate winds, partly cloudy skies, and isolated showers
prevail across the region this afternoon. Showers around a trough
about 200 miles to the east is gradually moving west towards the
Marianas. Buoy and altimetry data reveal combined seas between 5 and
7 feet.

Discussion...
A trend towards more unsettled weather is expected over the next
several days. A trough to the east is expected to bring scattered
showers and isolated thunderstorms starting later this evening. Then
this feature becomes more robust as overall convergence north of the
Near Equatorial Trough (NET) increases. Models show this feature
developing further around Tuesday and Wednesday once it has moved
past the Marianas off to the west. This development is linked to a
NET disturbance that may pull away to the north, meeting up with the
aforementioned trough. We will continue to monitor this developing
pattern since this may lead to more rainy days through the middle of
next week from the trailing convergence behind this possible
disturbance.

Marine/Surf...
Gentle to moderate trades prevail across the region through
Saturday, as a broad trough is expected to bring moderate to fresh
winds and an increase in showers Saturday night through Monday.
Combined seas of 5 to 7 feet build to 7 to 9 feet early next week as
a northerly swell arrives, generated by a distant low pressure
system. This, in turn, may cause the moderate risk of rip currents
along north and east facing reefs to increase to high early next
week as well.

Eastern Micronesia...
Not a lot seen across eastern Micronesia this afternoon. Low-end
scattered showers are seen across Kosrae and to the east of Pohnpei.
Isolated showers are found over Majuro. Buoys and altimetry show seas
between 5 and 8 feet.

Latest surface satellite data shows low-end scattered showers over
Kosrae that look to slowly clear through the evening, drifting west
into Pohnpei. This will result in drier conditions over Kosrae later
this evening at Kosrae with a brief period of scattered showers at
Pohnpei tonight. By Saturday morning, the dry pattern returns to
Pohnpei and both locations will see a period of drier weather. Models
continue to try to develop an Inter-Tropical Convergence Zone (ITCZ)
into the region over the weekend into next week. Satellite does show
an ITCZ east of the Date Line, where it has pretty much remained
over the past several days, occasionally drifting a little west of
the Date Line. Weak trade-wind troughs moving across the Date Line
will help enhance convergence over the region and could be the
kicker that actually gets the ITCZ started. Another key factor is the
location of the Near Equatorial Trough (NET) that is seen to the
south of Pohnpei and Kosrae. As the NET begins to drift west, this
will allow the approaching trade-wind troughs to maintain intensity
or strengthen a bit. Therefore, decided to go with the model guidance
somewhat, though kept the POPs (Probability of Precipitation) a bit
lower than the models liked. Overall, it does look like a more
unsettled pattern should move into the region over the weekend and
into next week.

For the marine environment, some changes were made to the forecast.
Overall, marine conditions are expected to deteriorate a bit over the
weekend as the trade-wind swell and a long-period north swell build
over the area. A very strong mid-latitude low pressure system will
produce a long-period north swell that is expected to arrive Sunday.
Then, over the next few days, the north swell looks to build a bit
more, with model guidance currently showing the swell reaching around
4 feet early next week. Along with the north swell, the northeast
trade swell will also build a bit. Combined seas are expected to
reach as high as 8 feet for Pohnpei and Kosrae and it is possible
that Majuro could see a brief period Sunday night with seas around
10 feet, especially over the northeast waters. Winds look to remain
mostly gentle to moderate with occasional fresh winds at Majuro.

Western Micronesia...
Satellite imagery shows fairly dry weather over Palau this evening as
the weak, elongated circulation noted yesterday has open back into
the Near Equatorial Trough (NET), with convection remaining fairly
inactive along the axis of the NET. Models continue to support a
fairly dry pattern at Palau through most of the weekend, but light
winds and daytime heating will continue to be supportive of isolated
island-effect showers, with an isolated thunderstorm possible in the
right conditions. Convergent flow north of the NET, along with a
passing trade-wind trough is generating scattered showers over Yap
this evening, with the occasional short-lived thunderstorm popping
up within the trade-wind trough. Expect showers to decrease to
isolated overnight as the trade-wind trough moves off to the west,
however, the overall pattern will continue to support periods of
scattered showers and isolated thunderstorms at Yap through Saturday
night, with a drier pattern expected Sunday and into the beginning of
the upcoming week. Across Chuuk, scattered showers and isolated
thunderstorms are being supported by the convergent flow north of the
NET and a trough passing through Chuuk and starting to move towards
the Marianas. As the trough lifts towards the Marianas, models show
convergence increasing behind the trough, increasing showers to
numerous briefly at Chuuk tonight and then decreasing back down to
scattered by Saturday. Models are also supporting a broad circulation
developing within the NET over the next few days that will shift
westward, pulling the NET with it, as the circulation appears to
follow the vorticity associated with the trough expected to move up
into the Marianas and then continue to move westward into the
Philippine Sea north of Yap and Palau. While models favor showers and
thundestorms mainly north of Palau and Yap late this weekend and
into next week, if the NET and trough decouple, then the potential
for showers may increase at Palau and Yap. Though the NET will move
way from Chuuk, trade-wind troughs exiting eastern Micronesia will
continue to support scattered showers and isolated thunderstorms
across Chuuk into the middle of the upcoming week.

Altimetry data indicates combined seas are around 4 to 5 feet near
Palau and Yap and 5 to 6 feet near Chuuk. Winds are fairly light
around Palau, while still gentle to moderate at Yap and Chuuk, with
some gusts to 25 kt in convection across Chuuk State. The northeast
trade swell is expected to remain fairly steady over the next several
day, but still expecting a long-period north swell to move into the
region late this weekend or early next week, which will build surf
along north-facing reefs. Wave models support most of the energy of
the north swell will be near and east of Chuuk, so surf will remain
below hazardous levels of 9 feet at Palau and Yap, but depending on
the the strength of the primary northeast trade swell, surf may push
up to 9 feet at Chuuk along north-facing reefs. Seas will peak
around 5 and 6 feet near Palau and Yap and around 7 to 8 feet at
Chuuk by the middle of the week. The next King Tide cycle is
expected to occur with the full moon on December 4th, meaning high
tides will be elevated a few days before and after the full moon.
This will increase the potential for some minor coastal inundation,
especially at vulnerable islands/atolls. Factors such as the current
La Nina pattern, and pulses of long-period swell are other factors
that can increase the risk of minor coastal inundation. During the
new moon back on November 20th, and the last King Tide cycle near the
beginning of November with the previous full moon, Chuuk did
experience some coastal flooding. While the upcoming King Tide cycle
is not expected to produce high tides as high as the King Tides back
in November, tides will be similar to the tides experienced during
the new moon, so this potential for coastal inundation is something
to watch for during the first week of December.

&&

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

$$


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