510
FXPQ50 PGUM 292053
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
653 AM ChST Sun Nov 30 2025

.Marianas Update...
The scattered showers and isolated thunderstorms moved through the
Marianas, leaving us with a soak-u-lent 0.02 inches... sigh. We may
have picked up a couple of tenths after midnight. And now, both
radar and satellite are mostly empty upstream. Showers could always
redevelop of course, there`s still a trough upstream. Took a look at
the 1.5 inches of QPF in the grid today and called up DESI. That was
more than even the highest member of the Grand Ensemble gave. So, had
to take today and the next couple of days weather down a notch, left
it scattered though, because the trough remains upstream. It will
just be less than had been expected.

&&

.Marine...
The marine forecast for the Marianas is pretty much right on track
and no changes were needed. Combined seas of 6 to 8 feet will grow to
between 7 and 9 feet over the next few days. There`s a high risk of
rip currents along east reefs, which could spread to north reefs and
require a high surf advisory, but hasn`t done so yet.

&&

.Eastern Micronesia Update...
No changes were made to the forecast this morning. Clouds are
evaporating over Pohnpei, and Kosrae remains fairly clear, so those
two forecasts are working great. Majuro is fairly clear right now as
the expected scattered showers are lurking to the south. They could
easily move back in. It`s mainly speed convergence of the trades with
possibly a hint of an Inter Tropical Convergence Zone driving this
activity in the Marshalls. Upper-level divergence seems to be the
driver for the scattered showers and isolated thunderstorms northeast
of Pohnpei.

&&

.Western Micronesia Update...
No changes were made to the forecast for Western Micronesia. The
showers at Chuuk are looking a bit sparse, but figured they could
redevelop, so re-issued the forecast of scattered. Oddly, Koror has a
weak circulation right near them, but there is hardly any convection
with it. This is going to allow for mostly sunny skies with isolated
showers at both Yap and Koror, which matched well with the inherited
expectations.

&&

.Tropical Systems...
JTWC`s Invest Area 93W is a highly stretched and disorganized thing,
but it is still a thing. It apparently has 2 circulation centers, one
south-southwest of Chuuk near 2N148E, and one near Koror Palau at
6N135E, with a trough connecting them. All the convection is to the
northeast, slightly northeast of the Chuuk center, and far northeast
of the Koror center, mostly associated with a couple of trade-wind
troughs moving through the Marianas. A tropical system with no
convection is one that`s not developing, so no change is expected in
the near term, other than that it might gradually drift westward or
west-northwestward.

.Prev discussion... /issued 613 PM ChST Sat Nov 29 2025/

Marianas Synopsis...
Visible satellite and radar imagery show scattered showers and
isolated thunderstorms across the region, mainly focused across Guam
and Rota coastal waters this afternoon. Buoy and altimetry data
reveal seas between 5 and 6 feet.

Discussion...
ASCAT analysis shows a trade-wind trough across western waters
earlier today, which continued to propagate westward this afternoon.
This brought an increase in scattered showers and several
thunderstorms near Guam and Rota today. Satellite and model trends
indicate an area scattered to numerous showers and isolated
thunderstorms developing to the east as trade-wind convergence
strengthen north of Invest 93W, a weak tropical disturbance to the
southeast. As 93W moves south of Guam over the next few days, this
will attribute an unsettled weather pattern across the Marianas. An
increase to numerous showers are expected later tonight for Guam and
Rota and after midnight for Tinian and Saipan. A peak in showers are
expected Sunday with gusts to 30 mph and locally showers possible for
Guam and Rota Sunday. Scattered to numerous showers continue through
early next week, then trade convergence following this disturbance
may prolong showers near Guam and Rota through the midweek.

Marine/Surf...
Combined seas of 5 to 7 feet are expected to build to 7 to 9 feet
Sunday as northerly swell arrives, generated by a distant low
pressure system. There will be a moderate risk of rip currents along
north and east facing reefs of the Marianas through tonight. Then,
the arrival of long-period north-northeast swell will increase surf
along north and east facing reefs over the next few days. The rip
risk increases to high along east facing reefs first, then surf along
north-facing reefs may increase to the high rip risk and high surf
thresholds (9 foot surf along north facing reefs) Sunday night and
Monday. As for now, a High Risk of Rip Currents will be in effect
Sunday morning through Wednesday afternoon.

Tropical Systems...
A weak disturbance, JTWC Invest 93W, is centered near 9N148E. This
feature is currently more of an open trough, extending north from a
weak buffer circulation near 1N149E to end near 12N148E. Invest 93W
looks to move toward the west-northwest over the next few days,
possibly becoming a weak circulation north of Yap and Palau early
next week. Invest 93W will be monitored closely over the next few
days for any indication of more rapid development.

Eastern Micronesia...
Mostly cloudy skies with low-end scattered showers and isolated
thunderstorms are seen across Pohnpei this evening. Partly cloudy
skies with isolated showers are present over Kosrae and Majuro.
Buoys show seas of 4 to 5 feet at Kosrae and Pohnpei, while altimetry
shows seas of 4 to 5 feet for Pohnpei and Kosrae and 6 to 9 feet
east of Majuro.

Models continue to overestimate rainfall across eastern Micronesia.
This is due to the expected development of an Inter-Tropical
Convergence Zone (ITCZ) that hasn`t materialized. There is now a weak
ITCZ that extends from the Date Line to just north of Majuro.
However, not much convection is seen with this feature yet. There are
scattered showers and isolated thunderstorms to the east of Majuro
that look to move over the atoll later tonight. Low-end scattered
showers and isolated thunderstorms are then expected to continue into
the beginning of next week. A drier pattern is then expected to
return to the atoll and continue through at least the middle of next
week.

For Kosrae, a dry pattern looks to continue through Sunday. Beginning
Sunday night, weak trade-wind troughs passing through the state look
to bring periods of scattered showers, with POPs (Probability of
Precipitation) mostly in the 30 to 40% range. However, there will be
times when the POPs drop to around 20%. Although models want to bring
the ITCZ west into Kosrae, and later into Pohnpei, this doesn`t look
likely. If the ITCZ does strengthen westward, POPs will need to be
increased.

For Pohnpei, an outflow is pushing northeast from a convective
complex to the southwest of the island. As this outflow approaches, a
band of weak convergence is producing scattered showers and a couple
thunderstorms within the coastal waters. Scattered showers and
isolated thunderstorms look to continue there through tonight. By
Sunday morning, a drier pattern looks to move in from Kosrae,
resulting in isolated showers Sunday and Sunday night.

Gentle to moderate winds are expected at Kosrae and Pohnpei through
the middle of next week. For Majuro, gentle to fresh winds are
expected through the middle of next week.

Sea and surf conditions will undergo changes over the weekend.
Trade-wind swell looks to slowly build 1 to 2 feet across eastern
Micronesia while a long-period north swell also enters the region.
The northeast trade swell is expected to reach 8 feet at Majuro, 7
feet at Pohnpei and 6 feet at Kosrae. This swell could reach high
enough to produce hazardous surf conditions of 8 feet along east
facing reefs on Kosrae, depending on the easterly component of the
swell. The north swell is expected to arrive by Sunday afternoon,
climbing from 3 feet Sunday afternoon to 5 feet by Monday morning,
with a period of 14 seconds. Another King Tide cycle will also occur
beginning around Tuesday afternoon, with the highest tides on
Thursday. With the long-period north swell combined with the King
Tide cycle, minor coastal inundation is expected along north facing
reefs of Majuro, especially within the lagoon, including the airport.
Residents of Majuro should take this time to ensure that property is
removed from coastal flood prone areas.

Western Micronesia...
Satellite imagery shows an area of scattered showers and isolated
thunderstorms, centered around 7N138E, to the east of Palau and south
of Yap Proper. The CIMSS 500 MB relative vorticity product shows and
area of increased vorticity over this location, indicating there is
vertical lift that is helping to support this area of convection.
Models suggest this area of showers will shift northwest, bringing
scattered showers and isolated thunderstorms to Palau and Yap later
tonight, and then as the 500 mb vorticity weakens, the convection
will diminish and for both locations Sunday, though light winds may
trigger some isolated island-effect convection during peak heating
hours at Palau. Across Chuuk, scattered showers and isolated
thunderstorms continue to be supported by the convergent flow north
of the NET trailing behind the trough (being monitored as Invest 93W)
that is moving into the Marianas. Models supporting a very broad
circulation developing within the NET over the next few days that
will shift westward, following the vorticity associated with the
trough as it moves through the Marianas and then continue to move
westward into the Philippine Sea north of Yap and Palau, potentially
also developing into a circulation . While models favor showers and
thunderstorms mainly north of Palau and Yap, convergence along the
circulations will bring scattered showers and isolated thunderstorms
to Palau Sunday night and Monday, and into Yap starting around Monday
night. Though the NET will move way from Chuuk, models suggest trade-
wind troughs exiting eastern Micronesia will continue to support
scattered showers and isolated thunderstorms across Chuuk trough the
middle of the upcoming week. However, as noticed in the eastern
Micronesia discussion, models have been overestimating rainfall for
that region, which could also mean they are overestimating rainfall
for Chuuk next week, so this will be a trend to watch over the next
couple of days.

Altimetry data combined seas are around 4 to 5 across the region.
The primary 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 around Monday, 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
there is still the potential for surf to push up to 9 feet at Chuuk
along north-facing reefs around Tuesday. 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. Based on current tide
predictions, this risk will peak Thursday, December 4th to about
Monday, December 8th.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...High Rip Current Risk through Wednesday afternoon for GUZ001.

MP...High Rip Current Risk through Wednesday afternoon for MPZ001>003.

Marianas Waters...None.
&&

$$


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