179
FXPQ50 PGUM 022025
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
625 AM ChST Mon Nov 3 2025

.Marianas Update...
Satellite early this morning shows isolated showers across the
Marianas, with surface observations and scatterometry indicating
gentle to moderate trade winds across the area. Winds are still
expected to increase this afternoon, but were decreased slightly in
the forecast according to latest observations and model trends. The
Small Craft Advisory will still be in effect today, as frequent
strong gusts will maintain elevated, choppy seas and conditions
hazardous to small craft through the afternoon. Otherwise, there was
very little change to the forecast. Buoys and altimetry indicate
combined seas of 6 to 8 feet around the islands early this morning.

Tropical Systems Update...
Tropical Storm Kalmaegi continues to move westward across the
Philippine Sea and is currently located near 11N130E, west of Yap
and north-northwest of Palau. TS Kalmaegi is expected to exit west of
Guam`s Area of Responsibility (AOR) later this morning, but some
effects will still be felt within the region. Westerly swell
generated by Kalmaegi will increase surf and seas at Palau and Yap
this week, while the monsoon trough extending through TS Kalmaegi and
across western Micronesia will support a wet pattern across the
region. For further details on TS Kalmaegi, please refer to the
public advisory issued by the National Weather Service under WMO
header WTPQ31 PGUM and the warning from the Joint Typhoon Warning
Center under WMO header WTPN31 PGTW.

&&

.Eastern Micronesia Update...
Little change was needed to the forecast. Satellite reveals overall
quiet conditions and isolated to scattered showers across the region
early this morning. A weak shallow trough will increase showers near
Majuro today and tonight as it propagates west through the area.
Buoys and altimetry indicate combined seas of around 3 to 5 feet.

&&

.Western Micronesia Update...
Satellite reveals numerous showers across Yap State between Yap
Proper and Chuuk, associated with a weak circulation embedded within
the monsoon trough that stretches across the region. Chuuk remains
along the eastern edge of the monsoon trough with most of the
convection focused further west. Showers are still expected to
increase today and tonight for Chuuk, but were decreased slightly in
the forecast based on latest observations and model trends,
maintained at numerous with wording for locally heavy showers.
Altimetry indicates combined seas around 4 to 6 feet across the
region.

&&

.Prev discussion... /issued 637 PM ChST Sun Nov 2 2025/

Marianas Synopsis...
Moderate to fresh trades prevail across the region. Satellite imagery
indicates a hastened trade-wind pattern bringing some isolated
showers across the waters. Buoys and recent altimetry passes show
seas are 6 to 8 feet.

Discussion...
A tropical disturbance developing in central Micronesia, is expected
to move toward the Marianas in the next few days and bring heavy
downpours, thunderstorms and strong gusty winds to the area around
midweek. After a brief period of breezy conditions Monday (trade-wind
surge induced), winds and showers will increase once again beginning
Tuesday, with heavy showers likely coming into the second half of the
week. Based on current projections, once this system exits the region
to the west, feeder bands along the leeside of the system may bring
an extended period of rainfall for the rest of the week. As such,
shower and thunder coverage may remain elevated coming into next
week. As this system remains largely disorganized with little to no
low-level circulation center (LLCC) visible yet on satellite
imagery, high uncertainty remains in its potential development at
this time. Various agencies will continue to watch this feature over
the coming days.

Marine...
A combination of an incoming trade-wind surge and elevated trade
swell, conditions are expected to become hazardous to small craft
Monday. As such, a Small Craft Advisory is issued for Monday for
winds of 20 to 25 kt. Combined seas of 6 to 8 feet are expected to
briefly peak at 9 feet Monday, then persist until midweek. Then, a
passing tropical disturbance may bring conditions hazardous to small
craft once again beginning Tuesday night, potentially lasting through
at least Thursday as the disturbance passes. A moderate risk of rip
currents is expected along north and east facing reefs of the
Marianas through at least midweek. After, a tropical disturbance and
leeside southeasterly to southerly flow may introduce a moderate rip
current risk along south facing reefs, and a high rip current risk
along east facing reefs by the weekend.

Hydrology...
Moderate uncertainty remains regarding potential rainfall impacts
from the developing tropical disturbance near Chuuk. Early estimates
indicate this system to bring locally heavy rainfall of 5 to 8
inches across the Marianas by the weekend. This feature will be
monitored closely over the next several days by various agencies, so
expected rainfall totals may change. Even so, flash flooding remains
a possibility Wednesday through Saturday. As showers are likely to
persist, consistent rainfall is likely to saturate the soils enough
to increase mudslide risk by the weekend, especially at Guam.
Residents on these islands need to closely monitor this developing
situation as flood watches, advisories and flash flood warnings could
be issued later.

Tropical Systems...
Tropical Storm Kalmaegi is steadily moving westward and is currently
located 11N133E, west of Yap and north-northwest of Palau. TS
Kalmaegi expected to continue to move westward across the Philippine
Sea and towards the Philippines as it moves away from western
Micronesia. Westerly swell generated by Kalmaegi will increase surf
and seas at Palau and Yap this week, while the monsoon trough
extending through TS Kalmaegi and across western Micronesia will
support a wet pattern across the region. For further details on
Kalmaegi, please refer to the public advisory issued by the National
Weather Service under WMO header WTPQ31 PGUM and the warning from the
Joint Typhoon Warning Center under WMO header WTPN31 PGTW.

The Joint Typhoon Warning Center closed Invest 99W earlier today as
the convection that was associated with 99W has dissipated. The
eastern extent of the monsoon trough across Chuuk State will be
monitored over the next several days as models support a potential
tropical disturbance/circulation developing within the trough around
midweek.

Eastern Micronesia...
A dry trade-wind pattern is in place across Majuro and Kosrae this
evening. However, Pohnpei is seeing scattered showers and isolated
thunderstorms as a weak trade-wind trough moves through and interacts
with upper-level divergence. The convection over Pohnpei looks to
subside overnight as the trough passes the island, with the dry
pattern moving into Pohnpei Monday morning and continuing through
Thursday. For Majuro, a weak trough to the east is expected to slowly
move through the Marshalls, bringing increased showers to the atoll
Monday into Monday night. There will then be a brief dry period
before a series of trade-wind troughs move through the region,
resulting in another increase in convection Tuesday night. Models are
also trying to develop another Inter-Tropical Convergence Zone
(ITCZ) over the Marshalls around midweek. There is low confidence in
where the ITCZ will develop, so decided to keep POPs (Probability of
Precipitation) at 40 to 50%. For Kosrae, the series of troughs look
to move into the area Tuesday night, ending the dry pattern through
the end of the week. Pohnpei should see the end of the dry period
around the end of the week.

Seas look to begin to increase over the region through the week. At
Pohnpei, seas of 3 to 4 feet this evening will begin to build
overnight reaching 4 to 6 feet by Thursday. For Kosrae, the building
seas will be a bit slower, with seas reaching 4 to 6 feet there near
the end of the week. With a 6 foot northeast swell, Kosrae could see
hazardous surf conditions Friday into the weekend. At Majuro, seas of
3 to 4 feet will also begin to build tonight, reaching 6 to 8 feet
Wednesday night into Thursday, then begin to subside a bit. Seas are
expected to drop to between 5 and 7 feet Thursday night into the
weekend. These building seas are in response to a trade-wind surge
to the northeast resulting in a building trade-wind swell. Light to
occasional gentle winds at Pohnpei and Kosrae will increase to gentle
to moderate later in the week, while Majuro will see gentle to
moderate winds through the week.

Western Micronesia...
Tropical Storm Kalmaegi continues to steadily move westward across
the Philippine Sea towards the Philippines and away from Yap and
Palau. While the monsoon trough extending through Kalmaegi and across
western Micronesia is supporting scattered showers and thundestorms
across Palau, eastern Yap State, and Chuuk State, the weather has
been fairly dry over Yap Proper today. The Blended TPW satellite
product shows similar precipitable water (pw) vales across Palau and
Yap, but looping various low-level water vapor and pw satellite
products, shows divergent flow over Yap, suggesting there may be some
low- to mid-level subsidence that is helping to suppress showers and
thunderstorm development at Yap this evening. As Tropical Storm
Kalmaegi continues westward, the divergent flow over Yap is expected
to weaken overnight, and with the monsoon trough extending across the
region, scattered showers and isolated thunderstorms are expected to
develop across Yap later tonight. The overall monsoon trough/pattern
will support scattered showers and isolated thunderstorms across
Palau and Yap through most the week, with gentle to moderate westerly
winds for the first half of the week. Around midweek, models show a
strengthening in the monsoon flow as a broad tropical
disturbance/circulation develops in or near Chuuk State, which will
cause winds to become moderate to fresh, with some gusty winds
possible, especially near showers and thunderstorms.

Chuuk sits on the eastern edge of the monsoon trough and satellite
imagery shows scattered to numerous showers and isolated
thunderstorms, mainly between the equator and 8N and to the west of
Chuuk Lagoon this evening. Over by Pohnpei, a weak trade-wind trough
is moving westward and is being supported by upper-level divergence.
Overall model guidance supports the monsoon trough and the
approaching trade-wind trough to support numerous to widespread
showers across Chuuk State Monday through Tuesday, with occasional
gusts around 25 to 30 kt possible in heavier showers. With Chuuk
Lagoon sitting the the eastern edge of the monsoon trough, any
westward shift in the monsoon trough could make the difference
between numerous to widespread showers developing over Chuuk Lagoon
or quickly pushing west of the lagoon, so watch for any short-term
updates to the forecast. A broad tropical disturbance/circulation is
expected to develop within the monsoon trough and starts to lift
towards the Marianas around midweek. This will steadily pull the
monsoon trough westward, and lead to a slow but steady decrease in
showers across Chuuk State, from east to west, later this week.

A steady northeast swell extends across the region, driven by the
elevated the trade winds in the central and western Pacific, mainly
north of 10N, due to the strengthen pressure gradient as a ridge of
high pressure develops in the mid-latitdues northwest of Hawaii. Seas
are currently 4 to 6 feet around Chuuk. Tropical Storm Kalmaegi and
the westerly monsoon flow are generating a westerly swell that will
be impacting Yap and Palau for most of the week. Surf will be
elevated on the west of the islands, but current forecast keep surf
below hazardous level of 9 feet. The westerly swell and winds will
also support elevated seas, but through at least Wednesday, winds are
expected to remain around 5 to 15 kt across Palau and Yap, below
hazardous levels of 22 kt, with seas around 5 to 7 feet, below
hazardous levels of 10 feet. Around Wednesday night and Thursday,
models show an increase in winds across Palau and Yap as a broad
tropical disturbance develops in or near Chuuk State. This will push
winds up to fresh (~20 kt) and likely cause seas to build 1 to 2
feet. This is still just below hazardous conditions to small craft,
but this will be a trend to monitor over the next few days.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...None.
MP...None.
Marianas Waters...Small Craft Advisory from 6 AM this morning to 6 PM ChST this
     evening for PMZ151>154.

&&

$$


Marianas/East and West Micronesia/Tropical Update: DeCou
Marianas: Montvila
East Micronesia: Kleeschulte
West Micronesia/Tropical: Schank