492
FXPQ50 PGUM 032003
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
603 AM ChST Thu Dec 4 2025

.Marianas Update...
A dry trade-wind pattern extends across the Marianas this morning,
with overall winds speeds expected to be around 10 to 15 mph over the
next several days. Model guidance still supports a weak trade-wind
trough passing near or south of Guam tonight and into Friday,
supporting a period of scattered showers and isolated thunderstorms
around Guam and Rota, while likely passing far enough south that
showers will remain isolated at Tinian and Saipan. Once this trough
passes west of the Marianas, dry weather will return as the region
continues its transition into dry season, typically extending from
late December to early May.

Seas are around 5 to 7 feet, supported by the elevated trade swell
and slowly subsiding longer-period north swell, with gentle to
moderate winds across the region. The high risk of rip currents has
ended along north and east facing reefs as surf has dropped below 9
feet. Sea and surf conditions are not expected to change much through
Friday night, but another pulse of northerly swell this weekend,
along with a slight increase in the trade swell, will help to push
seas up to 6 to 8 feet around Saturday and rebuild surf along north
and east facing reefs. Current model projects keep surf just below 9
feet, but a slightly increase in either swell could cause surf to
build to 9 feet, bring back the potential for high surf along north
facing reefs and a high risk of rip currents along north and east
facing reefs. A weak trough is expected to pass near or just south
of the Marianas tonight and Friday. The greatest potential for
scattered showers and isolated thunderstorms will be across Guam and
Rota coastal waters.

&&

Tropical Systems Update...
Invest 93W has shifted west-southwest overnight and is now located
near 13N132E. The low-level circulation still appears to be broad,
with deep, flaring convection now located along the western flank of
the system, associated with mid-level turning. The potential for
develop remains medium, meaning tropical cyclone development is
likely but beyond 24 hours. Invest 93W is expected to drift west-
southwest sliding under the strong north to northeast flow
associated near and behind a cold front, located north of the system.
Warm SSTs (Sea Surface Temperatures) and sufficiently-low wind shear
should allow for a slow but gradual intensification through the next
48 hours. This feature will likely exit Guam`s AOR (Area of
Responsibility, which ends at 130E) sometime late Friday or over the
weekend. For more information on Invest 93W, see bulletins issued by
the Joint Typhoon Warning Center under WMO header ABPW10 PGTW.

&&

.Eastern Micronesia Update...
A fairly dry trade-wind pattern extends across the region, though
scattered showers are still lingering within Pohnpei waters but
should clear out later this morning. A band of convergence extends
from the Date Line and towards the Marshall Islands, generating
scattered showers and isolated thunderstorms. Model guidance suggest
this band of convergence will hold together, starting to move into
Majuro this afternoon, but the greatest potential for showers and
thunderstorms looks to be tonight. Otherwise, an overall dry pattern
is expected across eastern Micronesia, with showers mainly
associated with passing trade-wind troughs.

Altimetry and buoy data suggest seas are around 6 to 8 feet across
the region. The High Surf Advisory for north facing reefs of Pohnpei
and north and east facing reefs of Kosrae remain in effect through 4
PM Friday, with a Coastal Flood Statement still in effect for Majuro
as well, due to elevated tides associated with the King Tide cycle
occurring as a long-period northerly swell is impacting the region.
These advisories may need to be extended into the weekend, as model
guidance continues to show another push of north to northeasterly
swell arriving by the weekend, keeping high surf a concern, while
tides will still be elevated for a few days after the full moon
tonight. Winds will remain mainly in the moderate to occasionally
fresh range through the period.

&&

.Western Micronesia Update...
A band of convergence is producing scattered showers and isolated
thunderstorms across Chuuk this morning and is extending towards
Yap, as it trails behind Invest 93W. Showers are currently isolated
at Yap Proper but are expected to increase this afternoon, along with
the potential for isolated thundestorms. Convergent westerly flow
south of the NET still extends across Palau but showers have so far
been fairly shallow and more spotty in nature as heavy convection has
dissipated overnight. Models support convection redeveloping south
of the NET but have trended more towards the west of Palau, so
reduced the potential for showers from 40 percent to 30 percent and
delayed isolated thunderstorms to the afternoon.

The convergent flow across Chuuk is expected to shift westward and by
Friday morning, a dry trade-wind pattern is expected to move in and
remain over the state through the beginning of next week. Showers
look to remain scattered at Yap through the next few days as
the NET drifts west along with the weak circulation currently between
of Koror and Yap. For Palau, as the NET drifts west, scattered
showers are expected to continue at Palau through Saturday. Due to
the instability over the region, isolated thunderstorms remain in the
forecast through the same time periods. The dry pattern moving into
Chuuk is then expected to move into Yap Saturday and Palau Saturday
night into Sunday.

For Chuuk, combined seas of 5 to 7 feet are expected to continue
through the weekend. This will be a combined northeast trade swell
and long-period north swell. The north swell is expected to build to
around 4 feet by Friday. The long-period north swell and the
northeast trade swell will combine with a King Tide cycle to produce
minor inundation along north and east facing reefs of Chuuk. For now,
the coastal flooding is expected to be around 1 foot and last into
the weekend. However, if the north swell lasts longer, the Coastal
Flood Advisory may need to be extended. For Palau and Yap, combined
seas of 3 to 6 feet are expected for the next few days. Over the
weekend, another round of north swell is expected to move into both
Yap and Palau and could result in hazardous surf conditions along
north facing reefs.

&&

.Prev discussion... /issued 630 PM ChST Wed Dec 3 2025/

Marianas Synopsis...
Satellite imagery shows partly cloudy skies and radar imagery shows
isolated showers over the Marianas. Altimetry shows seas of 6 to 8
feet while buoy data shows 7 to 8 feet. The High Surf Advisory (HSA)
and a High Risk of Rip Currents statement (HRRC) remain in effect.

Discussion...
Mostly pleasant weather for the forecast period. Winds are expected
to be 15 to 20 mph for the next 24 or so hours and will gradually
taper down to 10 to 15 mph by the end of the week. The winds are
expected to build up to 15 to 20 mph again for the weekend. The next
chance for scattered showers is anticipated to be a passing trade-
wind trough around Thursday night into Friday morning. Then it is
right back to a typical dry season pattern.

Marine...
Moderate to fresh trades and combined seas of 7 to 9 feet are
expected to decrease slightly as the elevated trade winds east of
the region weaken, and the long period northeast swell subsides.
Winds are expected to become gentle to moderate Thursday, with
seas decreasing to 5 to 7 feet. As a trough passes near the
Marianas around Thursday night and Friday, scattered showers are
expected to move into the waters with isolated thunderstorms
possible for Guam and Rota coastal waters.

The surf remains around the 7 to 9 foot mark allowing for the high
surf advisory and high risk of rip currents statement to be extended
for the overnight hours. Surf is expected to drop below the 9 foot
criteria level over the next 12 hours. With that being said, surf
will remain elevated and rip current risk will drop to moderate once
these swells relax a bit.

Tropical Systems...
Invest 93W has been upgraded to a medium rating, meaning tropical
cyclone development is likely but beyond 24 hours. The system has
become more symmetric today and shows signs of improved poleward
outflow. Warm SSTs (Sea Surface Temperatures) and sufficiently-low
wind shear should Allow for a slow but gradual intensification
through the next 48 hours. Convective redevelopment is also underway
around the periphery of the circulation on all sides, also indicting
better organizational potential. This feature will likely exit Guam`s
AOR (Area of Responsibility, which ends at 130E) sometime late
Friday or over the weekend. For more information on Invest 93W, see
bulletins issued by the Joint Typhoon Warning Center under WMO
header ABPW10 PGTW.

Eastern Micronesia...
Surface convergence is waning at Pohnpei and is minimal near Kosrae
and Majuro. This will continue into early next week, with most
locations only seeing isolated showers most of the time.

The bigger story will be seas and surf. We decided to extend the
advisories there through 4 PM Friday for the north shores of Pohnpei
and the north and east shores of Kosrae, with Majuro remaining in
Coastal Flood Advisory as well. These advisories may need to be
extended into the weekend, as model guidance continues to show
another push of north to northeasterly swell arriving by the weekend,
keeping high surf a concern. Winds will remain mainly in the
moderate to occasionally fresh range through the period.

Western Micronesia...
Latest satellite imagery shows isolated showers across Palau and
Chuuk, with low-end scattered showers over Yap. Altimetry data shows
seas between 6 and 9 feet near Chuuk, with 9 feet seen north of
Weno, and between 4 and 6 feet near Yap and Palau.

For Chuuk, a band of convergence extends northwest across Weno into
Invest 93W. Latest satellite data shows a break in the convection
over Weno, however, there are scattered showers and isolated
thunderstorms found northwest and southeast of the lagoon. This
convection is expected to move into Weno early in the evening,
continuing through Thursday night. By Friday morning, a dry trade-
wind pattern is expected to move in and remain over the state through
the beginning of next week.

For Palau and Yap, the Near-Equatorial Trough (NET) remains the
primary factor affecting the forecast for the next few days. The NET
extends east from near Mindanao, crossing 130E near 8N, into a weak
circulation northeast of Koror. It then turns southeast to beyond the
Equator near 147E. Most of the convection is currently south of the
NET, south of Palau, with a band of scattered showers over Yap.
Showers look to remain scattered at Yap through the next few days as
the NET drifts west along with the weak circulation northeast of
Koror. For Palau, as the NET drifts west, expect showers to increase
Thursday morning. Scattered showers look to continue at Yap through
Friday night and at Palau through Saturday. Due to the instability
over the region, isolated thunderstorms remain in the forecast
through the same time periods. The dry pattern moving into Chuuk is
then expected to move into Yap Saturday and Palau Saturday night into
Sunday.

For Chuuk, combined seas of 5 to 7 feet are expected to continue
through the weekend. This will be a combined northeast trade swell
and long-period north swell. The north swell is expected to build to
around 4 feet Thursday afternoon. The long-period north swell and the
northeast trade swell will combine with a King Tide cycle to produce
minor inundation along north and east facing reefs of Chuuk. For
now, the coastal flooding is expected to be around 1 foot and last
into the weekend. However, if the north swell lasts longer, the
Coastal Flood Advisory may need to be extended. For Palau and Yap,
combined seas of 3 to 6 feet are expected for the next few days.
Over the weekend, another round of north swell is expected to move
into both Yap and Palau and could result in hazardous surf conditions
along north facing reefs.

&&

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

$$


Marianas/East and West Micronesia/Tropical Update: Schank
Marianas: Bowsher
East Micronesia: Doll
West Micronesia: Kleeschulte