227
FXPQ50 PGUM 052046
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
646 AM ChST Mon Oct 6 2025

.Marianas Update...
The Marianas are setting up to be partly sunny with isolated showers
this morning. Seas of 2 to 3 feet, similar to what they have been.
Those could be about to increase thanks to the tropical disturbance
Invest Area 95W. Based on satellite though, 95W isn`t quite as
vigorous as the GFS seems to think it is, so I might take the under
bet on those sea heights...and the other items associated with the
passage of 95W on Tuesday.

&&

.Tropical Systems...
Tropical Storm 28W Halong has moved north of our Area of
Responsibility, so it will likely not be mentioned again in our
products, other than maybe a closing mention for the Tropical Weather
Discussion in several hours. For further information on Halong, refer
to warnings from the Joint Typhoon Warning Center under WMO header
WTPN32 PGTW.

Invest Area 95W is currently between the Marianas and Chuuk. The GFS
has really been liking it for development, perhaps a bit too much,
based on satellite presentation this morning, which is...
underwhelming. Information on 95W will be a bit hard to come by until
its organization begins to improve.

&&

.Eastern Micronesia Update...
The forecast for Eastern Micronesia was in good shape this morning,
based on the PacIOOS runup forecast though, put out a Coastal Flood
Advisory for Majuro. The forecast never gets to B level, so an
advisory for just minor or nuisance flooding or splashing seems
appropriate.

&&

.Western Micronesia Update...
Based on the underwhelming state of 95W, revised some precipitation
downward in Western Micronesia. Scattered showers becoming isolated
for Chuuk (they may actually be isolated already), and just isolated
today in Koror. Based on satellite, it seems 95W is struggling
currently.

&&

.Prev discussion... /issued 634 PM ChST Sun Oct 5 2025/

Marianas Synopsis...
Satellite and radar imagery show isolated showers across the coastal
waters, increasing slightly along the most southern edge of Guam`s
coastal waters, along some convergent flow. Cloud cover is
decreasing slightly over the islands as island-effect convection that
was driven by daytime heating continues to diminish. Winds remain
light and variable with combined seas around 3 to 4 feet.

Discussion...
For most of the day, a band of showers have been developing just
south of the Marianas, along an area of convergent flow created by
light southwest winds meeting the north to northeast flow around
Invest 95W, a disorganized tropical disturbance located near Chuuk
State. Models show this area of convergence lifting northward as
Invest 95W slowly drift northwest, increasing showers and the
potential for isolated thunderstorms across Guam and the CNMI. This
area of convergence is expected to weaken Monday morning, creating
similar conditions to earlier today, with weak winds across the
Marianas. This could trigger another round of island convection,
especially over Guam during the peak heating hours of the day,
especially if cloud cover associated with Invest 95W remains
southeast of the Marianas for most of the day. Model guidance
supports Invest 95W remaining disorganized as it drifts northwest and
passes through the Marianas around Tuesday. However, even if Invest
95W remains disorganized, there is still the potential for locally
heavy showers and thunderstorms and gusty winds as Invest 95W moves
through the region, so introduced numerous showers and gusts to 30
mph with locally heavy showers to the forecast for Tuesday. Invest
95W is expected steadily move northwest and pull away from the
Marianas by Wednesday, allowing for winds and the potential for
showers to decrease through Thursday. By Friday, models support
another trough approaching the Marianas, increasing the potential for
showers for the end of the week.

Marine...
Combined seas of 3 to 4 feet and light to gentle winds are expected
to build Monday night and Tuesday as a tropical disturbance (Invest
95W) approaches the region. The east swell is also expected to build,
and should cause a moderate risk of rip currents to develop along
east facing reefs Monday night. Though Invest 95W is expected to
remain disorganized, low visibility due to heavy rain, gusty winds
and choppy seas up to 8 feet are possible Tuesday. Seas and winds
will then decrease Wednesday as Invest 95W moves northwest and away
from the region. The east swell is also expected to subside slightly,
but the moderate risk of rip currents along east facing reefs may
linger through at least Wednesday night. An approaching TUTT cell
will continue to keep the risk of isolated thunderstorms in the
forecast for at least the next few days. Looking towards the weekend,
wave models show a long-period north swell entering the region,
likely generated by Tropical Storm Halong as it continue to develop
north of the region. Currently, wave models keep the swell around 2
to 3 feet, causing surf to be slightly elevated along north facing
reefs this weekend.

Tropical Systems...
TS Halong is now centered near 25N142E and has remained quasi-
stationary over the past several hours. Halong is expected to speed
up a bit and move west, hugging 25N for the next few days. Halong is
also expected to strengthen over the next several, possibly becoming
a typhoon Monday night or Tuesday. No direct impacts are expected
for the Marianas or Micronesia from TS Halong, though the Marianas
and western Micronesia may see a slightly elevated northerly swell
late this week, generated by Halong as it continues to strengthen.
For more information on TS Halong, please refer to bulletins issued
by the Joint Typhoon Warning Center under WMO header WTPN32 PGTW and
by the National Weather Service under WMO header WTPQ32 PGUM.

A broad disturbance, Invest 95W, is evident on satellite and the
latest ASCAT analysis to the northwest of Weno, Chuuk, centered near
11N151E. Latest model guidance indicates that, due to Invest 95W`s
current disorganized state, strengthening is not expected for the
next day or two as it drifts northwest. 95W is expected to pass
through the Marianas during the first half of the week. Guidance also
suggests that any development will be minor as the models struggle
to develop 95W as it moves northwest of the Marianas. Invest 95W will
be monitored closely over the next few days for any indication of
possible development.

Eastern Micronesia...
Eastern Micronesia started out fairly dry this morning, but that is
quickly changing for Kosrae and Majuro. The Inter-Tropical
Convergence Zone (ITCZ) is becoming more active along with a weak
trade-wind trough moving through Kosrae. Pohnpei is seeing mid-and
upper-level clouds spinning out of Invest 95W.

An active ITCZ is now affecting Majuro, producing scattered showers
and isolated thunderstorms across the atoll with increasing
convection moving in from the east. An elongated trough is seen to
the south and east of Majuro, interacting with the ITCZ to generate
this convection. The trough is expected to move into Majuro by early
Monday morning, with POPs (Probability of Precipitation) increasing.
Decided to keep POPs at around 50% for now, though this could change
by morning. If the ITCZ remains over Majuro as the trough moves
through, numerous showers are a possibility with locally heavy
showers. As of now, it looks like the trough will push the ITCZ a bit
farther north. The ITCZ and trough look to be out of the Marshalls
by Tuesday, allowing a dry pattern to move into the region. This dry
pattern looks to remain over the Marshalls through the end of the
week.

For Kosrae, a very weak trough approaching the island is producing
low-end scattered showers and isolated thunderstorms. These showers
may decrease to isolated for an hour or two, but another trough,
currently evident on satellite to the east of Kosrae, will result in
convection again increasing to scattered. The elongated trough over
the Marshalls also looks to move into the area Monday night,
maintaining low-end scattered showers and isolated thunderstorms
through Tuesday. POPs look to remain in the 20 to 30% range through
midweek, then the dry pattern over the Marshalls looks to move in for
the remainder of the week.

Pohnpei is sitting on the eastern edge of outflow from Invest 95W.
95W will help keep Pohnpei fairly dry through Tuesday night as most
of the moisture in the region will flow into it. Also, the slow
movement of 95W help hold back the other approaching troughs. Around
midweek, 95W is expected to be farther away from Pohnpei to no longer
have an effect, allowing increased convection to move into the area.
POPs look to increase into the 30-40% range Wednesday and Thursday
before the dry pattern moves in from Kosrae.

Overall, marine conditions look to remain benign, with light to
occasionally gentle winds. Combined seas of 3 to 4 feet are expected
for Pohnpei and Kosrae, with 3 to 5 feet at Majuro. One thing worth
mentioning for Majuro, a full moon will occur Monday, thus producing
higher than normal tides. As of now, it appears that any inundation
will be minor. Models show a very small, around 1 foot, longer-
period south swell in the Marshalls arriving Monday or Monday night.
This swell is not expected to increase. However, if the swell does
increase, even as little as 1 additional foot, it could produce a
more significant inundation along south shores of up to 1 foot during
high tide. This will be monitored over the next couple of days.

Western Micronesia...
Invest 95W is still fairly disorganized across much of Chuuk State.
ASCAT analysis places a circulation near 11N151E, about 230 miles
northwest of Weno. However, model guidance does indicate an elongated
center and trough extending to the southeast, prolonging numerous to
widespread showers and isolated thunderstorms over Chuuk tonight and
Monday morning. Much of the showers have stratified over Weno this
afternoon, but are expected to increase again overnight, with gusts
to 25 kt near heavier showers. Afterwards, showers are expected to
trend down to isolated Monday night and Tuesday as the 95W pulls away
to the northwest, then scattered showers build back in around
midweek as a fragment of the ITCZ lifts northwest into the area.

Farther west, showers and clouds are picking up over parts of
eastern Yap State, although showers are still isolated over Yap
Proper and Palau this afternoon. A shift towards wetter weather is
expected over the next few days as distant TS Halong and Invest 95W
continues to support a southwest monsoon-like pattern over Palau and
Yap. Showers are expected to become numerous at times, with locally
heavy showers possible. By late week, southwesterlies weaken as 95W
passes to the distant north, while a trade-wind pattern begins to
push in from the east, possibly prolonging scattered showers through
the weekend.

Scatterometry and altimetry data indicates, light to moderate winds
and combined seas of around 2 to 3 feet near Yap and Palau, and up to
4 feet near Chuuk. A pulse of southwest swell looks to build across
Palau waters Tuesday and into Yap Thursday, driven by a developing
monsoon-like pattern. Seas look to build to 3 to 5 feet around
midweek. Winds will remain mostly light to gentle at Yap and Palau,
becoming moderate to fresh at times Monday night through Tuesday
night. Towards the weekend, wave models show a long-period north
swell begining to enter Yap and Palau waters, emanating from distant
TS Halong. This is expected to build surf along north-facing reefs,
although no hazards are expected at this time. For Chuuk, gusts to
25 kt are possible tonight, otherwise light to moderate south to
southwest winds shift back to light to gentle trades by Tuesday
night.

&&

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

$$


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