108
FXPQ50 PGUM 101958
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
558 AM ChST Tue Aug 11 2026

.Marianas Update...
After a few rounds of locally heavy showers across Guam overnight,
radar and infrared satellite imagery early this morning show mainly
moderate showers moving across Guam and Rota. An embedded disturbance
within the monsoon trough to our north looks to keep unsettled
nearby, with periods of scattered locally heavy showers potentially
spreading southward across the Marianas today. Overall, no major
changes to the forecast today.

Marine conditions have subsided below hazardous criteria across Guam
and Rota waters, so the Small Craft Advisory was allowed to expire
this morning. Significant west swell from the monsoon pattern, mixed
with northwesterly and northeasterly swells, and large localized
wind waves are producing combined seas of 7 to 10 feet, maintaining
hazardous conditions to small craft across Tinian and Saipan waters
through at least Thursday afternoon. Hazardous surf and a high risk
of rip currents continue along west and north facing reefs through
Thursday afternoon, potentially dropping below hazardous levels
tonight along north-facing reefs.

&&

.Tropical Systems Update...
At 1am, Peilou (13W) was downgraded to a tropical depression. TD
Peilou was located near 22N154E, moving east-northeast at 20 mph,
continuing to move away from the Marianas. It is expected to make
a slight turn toward the northeast with little change in forward
speed through Wednesday. This general track passes southeast of
Minamitorishima today and exiting our Area of Responsibility (AoR)
this evening. For more information on Peilou, please refer to
bulletins from the Joint Typhoon Warning Center under WMO header
WTPN32 PGTW and from the National Weather Service under WMO header
WTPQ32 PGUM.

A tropical disturbance, Invest 90W, has moved slightly WNW to near
11N168E, over the northern Marshalls. 90W is still rated "sub-low",
meaning development is possible, but not expected over the next few
days. Convection is poorly organized around this disturbance, but
continues to influence the broader weather pattern across eastern
Micronesia.

&&

.Eastern Micronesia Update...
An unsettled pattern continues as Invest 90W remains situated across
the northern Marshalls and convergence increases within the westerly
flow across Pohnpei and Kosrae states. Only a few changes were made
to the forecast. Numerous to widespread locally heavy showers have
build in across Pohnpei early this morning, with showers expected to
increase to numerous at Kosrae around noon. Meanwhile, satellite
trends show a decrease in showers at Majuro, with only isolated
showers expected today. A High Surf Advisory remains in effect along
south-facing reefs of Kosrae through early Wednesday morning.

&&

.Western Micronesia Update...
No major changes were made to the forecast. Continue to expect fair
weather at Yap and Palau today. Meanwhile, showers are trying to
backbuild into Chuuk, tied to the unsettled pattern across eastern
Micronesia. Model guidance shows the bulk showers staying east of
Chuuk, so kept high-end scattered showers, but added locally heavy
showers possible today.

&&

.Prev discussion... /issued 525 PM ChST Mon Aug 10 2026/

Marianas Synopsis...
Moderate to strong westerlies prevail across the region. Satellite
imagery and Doppler radar indicate pockets of showers developing
across Guam and rota waters. Recent altimetry passes and SOFAR buoys
indicate seas are 8 to 10 feet.

Discussion...
A westerly monsoon push is expected to continue bringing heavier
showers and thunderstorms to the Marianas, especially to Tinian and
Saipan overnight. After, a convergence zone is expected to shift
farther south, bringing higher shower and thunder coverage to Guam
and Rota Tuesday. Once TS Peilou (formerly Kujira) shoots to the
north and away from the Marianas and another disturbance begins
consolidating northeast of Pohnpei, a diffusive southwesterly flow is
expected to develop across the region. This will allow a dry spell
to return, lasting until at least the weekend.

Marine...
Moderate to strong westerlies will prevail across the Marianas
tonight, will drop to gentle to fresh in Guam and Rota coastal
waters Tuesday, allowing seas to fall below 10 feet. As such, the
Small Craft Advisory is expected to expire late tonight for Guam
and Rota waters. Various significant northerly swells and large
localized wind waves, are expected to continue producing sea
conditions hazardous to small craft through at least Thursday
afternoon in Tinian and Saipan waters. However, seas may briefly
drop below 10 feet Tuesday night as winds slow and some swells
decrease, before another resurgence in the monsoon surge brings seas
back up Wednesday. When said monsoon surge returns, sea conditions
hazardous to small craft may return to Guam and Rota waters in the
second half of the week. Hazardous surf and a high risk of rip
currents are expected to continue along west and north facing reefs
through Thursday afternoon, as northwesterly and northeasterly swells
continue to mix in the region.

Tropical Systems...
Tropical Storm Peilou (formerly Kujira) continues to move at a fast
pace, away from the Marianas, with it`s current location near 21N151E
(roughly 300 miles northeast of the Maug Islands). This system will
not be a factor in our weather, aside from the persistent west to
southwest surface winds across the Marianas.

Then we have Invest 90W (rated as "Sub-Low" from JTWC - the Joint
Typhoon warning Center), and it`s located northeast of Kwajalein
(near 10.5N 169.4E). 90W continues to move very slowly, with both the
GEFS and ECENS having trouble locking onto the tropical disturbance.
There`s elevated convection near the western semicircle of the
circulation, and brief surface-based attempts south-southeast of the
LLCC. The GEFS and ECENS both show this system remaining
disorganized with their solutions reforming a center near 8N151E in
about 6 days. It`ll be interesting to watch, as the MJO (Madden-
Julian Oscillation) will be in a favorable location. It`s several
days out though, so plenty of time to watch it, as even a week out
it`s not forecast as any significant circulation. We`ll keep an eye
on it though over the next several days.

Eastern Micronesia...
Invest 90W continues to show improved westerly inflow, with an
elevated disturbance located on it`s southwest to west flank. This
along with the inflow is allowing for numerous to widespread shower
and thunderstorm development to affect Kosrae, and it`ll move into
Pohnpei`s area within the next 24 hours. As such, rainfall
potential/shower coverage was increased at both locations. Kosrae
also remains under a High Surf Advisory for the south-facing reefs,
as a pulse of energy south of the equator augments swell heights to
hazardous levels. This will continue through early Wednesday morning
at the very least, and this threat may persist a little longer.
We`ll keep an eye out for that potential. As for Majuro, isolated to
widely-scattered showers and perhaps a thunderstorm is all you can
look for over the next several days.

As for marine conditions, mainly light to gentle winds are expected
area-wide, with seas of 5 to 7 feet subsiding a foot for the latter
half of the week.

Western Micronesia...
Satellite observations show mostly clear to partly cloudy skies
across western Micronesia. Altimetry shows combined seas between 4
and 7 feet.

Overall, minimal changes were made with this forecast package. The
status quo will continue for Palau and Yap through the period with
surface ridging remaining in place. Yap could see some 20 PoPs
through Tuesday, but shower coverage is expected to remain isolated.
For Chuuk, an increase in showers is expected as the surface high
pressure shifts westward. Current satellite obs show an increasing
agitated cumulus field developing across Chuuk. Isolated showers are
expected to become scattered overnight. A relative lull in showers
activity is expected Wednesday and Thursday before increased shower
coverage returns towards the end of the week. This will be the
leading wave of a pattern change that looks to shake up the weather
across eastern Yap State just beyond the forecast period.

Combined seas are between 5 and 7 feet across western Micronesia and
seas are expected to fall 1 to 2 feet over the coming days. Benign
marine conditions will prevail through the forecast period.

&&

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

     High Surf Advisory until 4 PM ChST Thursday for GUZ001.

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

     High Surf Advisory until 4 PM ChST Thursday for MPZ001>003.

Marianas Waters...Small Craft Advisory until 5 PM ChST Thursday for PMZ153-154.

&&

$$


Marianas/East and West Micronesia/Tropical Update: Cruz
Marianas: Montvila
East Micronesia/Tropical: Doll
West Micronesia: Williams