398
FXPQ50 PGUM 030837
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
637 PM ChST Mon Nov 3 2025

.Marianas Synopsis...
Moderate to fresh easterlies prevail across the Marianas. Satellite
imagery and Doppler radar indicate a line of showers moving across
Guam waters, followed by a broad surface trough moving in from
upstream, as it interacts with upper-level features to produce
lightning. Buoys show seas are between 5 and 8 feet.

&&

.Discussion...
The tropical disturbance that is developing in central Micronesia and
remains to be the primary culprit for increasing weather across the
Marianas, is now known as JTWC`s Invest 90W. This system continues
to consolidate, and is expected to begin moving toward the Marianas
by Wednesday. As it approaches, shower and thunder coverage will
increase, with the heaviest showers and potentially stronger winds
expected to arrive by Wednesday night. Even with the consistent storm
motion trends, high uncertainty remains regarding wind impacts, as
the system remains largely disorganized. Even so, moderate to fresh
trades may become fresh to strong as early as Tuesday night, with a
chance for windy conditions to develop coming into the second half of
the week. Once certainty increases, a Wind Advisory may be issued
across the Marianas, if conditions warrant. After the system exits
to the west, feeder bands along the leeside of the system may bring
an extended period of rainfall for the rest of the week, but looks
like model guidance is going too aggressive on shower coverage
duration coming into the tail end of the forecast cycle.

&&

.Marine...
Sea conditions have improved steadily enough to no longer be
hazardous to small craft at this time. As such, the Small Craft
Advisory was cancelled for today. Combined seas of 5 to 7 feet are
expected to increase slowly over the next several days, before
picking up suddenly during 90W`s passage, potentially producing sea
conditions hazardous to small craft before the weekend.
A moderate risk of rip currents is expected along north and east
facing reefs of the Marianas through at least midweek. After,
southeasterly to southerly flow caused by 90W may introduce a
moderate rip current risk along south facing reefs, and a high rip
current risk along east facing reefs by the weekend.

&&

.Tropical systems...
A largely disorganized tropical disturbance, now known as JTWC`s
Invest 90W, is centered near 9N147E in eastern Yap State, just
northwest of Satawal. An open-cell configuration, with 15 to 20 kt
sustained monsoonal inflow, is expected to move into a very tight
neutral zone tucked between two massive wind shear zones that can
take apart the system; this neutral zone is situated right over the
Marianas. The shear tendency in this pocket of hope continues to
decrease, given that the system continues to meander in its general
vicinity while gaining steam prior to its exit to the north. At this
time, the Invest Area is designated as a Low, indicating that
development into a significant tropical cyclone within the next 24
hours is not likely. Model trends continue to show a signal for
intensification coming into the second half of the week, when the
eastern periphery rain bands will move in across the Marianas during
passage. Due to the lackluster nature of this system, high
uncertainty remains in the storm motion at this time.

For more information on Invest 90W please see the Significant
Tropical Weather Advisory bulletin for the Western/Southern Pacific
Ocean issued by the Joint Typhoon Warning Center under WMO header
ABPW10 PGTW.

&&

.Hydrology...
Moderate uncertainty remains regarding potential rainfall impacts,
but early estimates indicate this system to bring locally heavy
rainfall of 5 to 8 inches across the Marianas by the weekend.
With such rainfall, flash flooding remains a possibility Wednesday
through Saturday. Uncertainty regarding mudslide risk during the
weekend remains high. If feeder bands form, showers are likely to
persist into the weekend, which would become more likely to saturate
the soils enough to increase mudslide risk. Residents need to closely
monitor this developing situation as flood watches, advisories and
flash flood warnings could be issued later.

&&

.Eastern Micronesia...
A dry trade-wind pattern continues across eastern Micronesia with
only partly cloudy skies, spotty showers seen across the region.
Light to occasionally gentle trade winds are in place at Pohnpei and
Kosrae, with gentle to moderate winds at Majuro.Combined seas are 3
to 5 feet across the region.

Majuro looks to be the first to see increasing convection, with low-
end scattered showers expected Tuesday as a weak trough moves
through the area. Behind this trough, a series of trade-wind troughs
are expected to move through the Marshalls, maintaining increased
convection through Thursday. A drier period looks likely for Friday
before an Inter-Tropical Convergence Zone (ITCZ) moves in from east
of the Date Line. this should make for a wet weekend at Majuro.

For Kosrae, the dry pattern looks to continue a while longer, with
only isolated showers expected there through Wednesday night. By
Thursday, the trade-wind troughs moving through Majuro should drop
far enough south to bring increased convection to Kosrae. These
troughs are expected to keep the island in a wetter pattern at least
into the weekend.

For Pohnpei, the troughs will hold off a bit longer, with the island
maintaining a dry trade-wind pattern through Thursday. By Friday,
convection should increase as the first of the troughs makes its way
through. A wetter pattern is then expected to remain at Pohnpei
through the weekend.

Combined seas of 4 to 6 feet are seen at Majuro, with seas building
fairly quickly to between 6 and 8 feet by Wednesday. This is due to
a trade-wind surge producing increased trade swell over the region.
Seas are expected to peak at Majuro Wednesday night, but remain
elevated into the weekend. Due to higher tides over the next few
days, this building swell will bring minor coastal inundation to
Majuro and other islands and atolls in the Marshalls, with 1 to 2
feet of inundation expected Tuesday into the weekend. A Coastal
Flood Advisory has been issued with inundation starting Tuesday
afternoon. Winds will be gentle to moderate into the weekend.

For Pohnpei, seas of 3 to 4 feet will slowly build due to the trade-
wind surge, reaching around 6 feet Thursday into the weekend. Kosrae
will see combined seas of 3 to 4 feet through Wednesday night, when
seas begin to slowly build, reaching 5 to 6 feet over the weekend.
This northeast swell could produce hazardous surf conditions along
east facing reefs over the weekend. Light to gentle winds at Pohnpei
and Kosrae will become gentle to moderate Wednesday into Thursday.

&&

.Western Micronesia...
The heaviest weather across the region is currently over eastern Yap
and western Chuuk States, within the monsoon trough and around the
embedded circulation being monitored by JTWC as Invest 90W, located
near 9N147E. Satellite imagery showers numerous locally heavy
showers and isolated thunderstorms across the outer islands with
scatterometer wind data showing a westerly wind burst around 20 to 30
kt this morning south of Invest 90W. These showers and winds are
creating hazardous conditions that will make inter-island travel in
eastern Yap State and western Chuuk State difficult and at times
dangerous. Model guidance shows that Invest 90W will likely
consolidate slowly, with little likelihood of developing into a
significant tropical cyclone over the next 24 hours, though heavy
convection will continue to build over the eastern islands of Yap
State and into western Chuuk State. Invest 90W is expected to slowly
move northwest, dragging the monsoon trough north and west, pulling
the strong monsoon winds and heavy showers away from Chuuk State and
further west across Yap State.

Chuuk Lagoon currently sites on the eastern edge of the monsoon
trough so winds are more southerly and weaker, around 10 to 15 kt,
with scattered showers and isolated thunderstorms this evening. Over
the past couple of hours satellite imagery shows cooling cloud tops
in the easter waters of Chuuk which suggest convection is increase,
so expect showers to become numerous overnight with some occasional
gusts to 25 kt possible in heavier showers. As Invest 90W and the
monsoon trough move north and west, winds will become more southeast
at Chuuk and the risk for heavy showers and strong winds will shift
westward over the next few days, though convergent flow into the
monsoon trough and 90W will continue to support a wet pattern across
Chuuk. Palau and Yap Proper are currently experiencing mostly cloud
skies but showers currently isolated with diffuse flow over both
locations as Palau and Yap are currently between Typhoon Kalmaegi,
located west of 130E and near the Philippines, and Invest 90W in
eastern Yap State. As Kalmaegi continues to move away to the west,
models show convergence increase over the area which will support
scattered showers and isolated thunderstorms later tonight and over
the next couple of days. Models support Invest 90W moving in west-
northwest to north-northwest direction with trends largely
suggesting 90W passing between Yap and Guam Wednesday or Thursday,
though there is still a large degree on uncertainty in motion and
speed of development to to 90W`s current disorganized state. Overall,
this general motion will shift stronger monsoonal winds and the
potential for heavy showers towards Palau and Yap, especially during
the Thursday to Saturday time frame, with model guidance supporting
winds around 15 to 20 kt across Palau and potentially up to 25 kt at
Yap.

Altimetry data shows seas are around 5 to 7 feet across the region,
but are likely higher around Invest 90W where conditions are likely
nearing or meeting hazardous conditions of 22kt and seas of 10 feet
for small craft in eastern Yap State. The primary swell continues to
be the northeast swell, driven a trade-wind surge in the central
Pacific, with a secondary westerly swell generated by the monsoonal
flow of the monsoon trough that is also being enhanced by Invest 90W,
and by Typhoon Kalmaegi near the Philippines. Sea and winds are not
expected to change much around Chuuk the next few days as the
strongest winds and seas will likely slowly shift westward following
the monsoon trough and Invest 90W. Winds of 22kt and seas of 10 feet
are possible around Palau and Yap during the Thursday to Saturday
time period but this will depend on how Invest 90W develops and moves
over the next few days, but development over the next 24 hours into
a significant tropical cyclone is unlikely. Surf will be elevated
along west, north, and east facing reefs across the region but not
expected to exceed hazardous levels of 9 feet along west and north
reefs and 12 feet along east facing reefs through the next few days.
However, models show the northeast swell building near the end of the
week, with a potential north to northwest swell developing from
Invest 90W if it starts to organize. Surf conditions could become
hazardous along some reefs late this week or this weekend.

&&

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

&&

$$

Marianas/Tropical: Montvila
East Micronesia: Kleeschulte
West Micronesia: Schank