794
FXPQ50 PGUM 091955
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
555 AM ChST Thu Sep 10 2026

.Marianas Update...
Radar and satellite show partly cloudy skies and isolated showers and
isolated showers over the Marianas this morning. Altimetry shows
combined seas of 4 to 6 feet near the Marianas, composed of a 3 foot
west swell, a 3 foot east swell, and wind waves. Island effect could
make convection bubble up again later, took the weather out for this
morning though based on satellite and radar.

&&

.Marine...
Our marine grids match reasonbaly well with altimetry today and with
model data through Saturday, which is good enough for today. Things
get interesting further out. On Tuesday our grids have combined seas
of 2 feet, which is unlikely. It seems though that we`re attempting
to avoid incoming 10 plus foot seas on Wednesday. That could be
equally unlikely, as it seems to be related to a GFS tropical
cyclone, which are a dime a dozen. It`s worth noting though, that the
ECMWF-HiRes also has a tropical cyclone. Stay tuned... for now the
only thing we can say with certainty is that uncertainty is high.

&&

.Eastern Micronesia Update...
Majuro is looking fairly moist this morning, while Pohnpei and Kosrae
are being dry slotted. No changes were made to the forecast though,
because while Pohnpei and Kosrae are in the dry slot, satellite still
shows some low topped showers moving through, so retained the 30 and
40 percent scattered forecasts for today.

&&

.Western Micronesia Update...
The showers are remaining south of Chuuk, so took them down to
isolated for today. Yap and Koror both had forecasts of just isolated
showers already, so no changes were needed. There`s an impressive
blowup of showers not that far east of Yap, but it keeps refusing to
move in.

&&

.Prev discussion... /issued 607 PM ChST Wed Sep 9 2026/

Marianas Synopsis...
Visible satellite and radar imagery show isolated to numerous
showers and a rare case of scattered thunderstorms is visible over
the Marianas this evening. Gentle to moderate northeast winds are
prevailing. Buoy and model data suggest combined seas are around 4
feet.

Discussion...
A broad trough combined with moderate upper-level divergence of the
Marianas will continue to bring scattered thunderstorms early
tonight. While the trough will remain, models indicate upper-level
support will decrease overnight. Moisture will remain in the area
through Thursday but with thunderstorm coverage will likely tapper
down to isolated. Scattered showers and isolated thunderstorms
Thursday will become isolated through the weekend as more stable air
moves into the region. Moisture will remain high enough, however, for
island effects showers to be possible for at least Guam over the
next several days. By late weekend or early next week, model guidance
suggests a new disturbance may develop far south-southeast of the
Marianas, possibly bringing a new round of unsettled weather by the
end of the forecast period.

Marine...
Gentle to moderate northeast winds are expected to gradually
decrease this week. Combined seas are around 4 feet from a decreasing
west-northwest swell and an increasing east swell. Scattered showers
and thunderstorms tonight will become isolated thunderstorms after
midnight. Scattered showers and isolated thunderstorms will likely
return Thursday.

For coastal reefs, a moderate risk of rip currents will continue
along west-facing reefs. Based on the swells and buoy data, north
and south-facing reefs are no longer under a moderate risk. East
facing reefs may reach a moderate risk by Thursday afternoon as an
east swell builds into the Marianas. A high risk of lightning early
tonight will become moderate after midnight and persist through
Thursday.

Eastern Micronesia...
A monsoon trough stretches across much of eastern Micronesia this
afternoon and will promote periods of unsettled weather over the
coming days for all forecast locations. Numerous showers and
isolated thunderstorms are expected at Majuro through Thursday with
conditions then improving slightly Thursday night. Scattered showers
and isolated thunderstorms are expected at Kosrae and Pohnpei
through Thursday with conditions then deteriorating Thursday night
as a wet and unsettled weather pattern begins. Numerous showers
isolated thunderstorms will be possible on Friday and into the
weekend with locally heavy rainfall possible at both locations.

Moderate to fresh west to southwest winds are expected to continue at
all forecast points through tonight. Wind will begin to ease
slightly Thursday at Majuro and Kosrae, becoming mostly moderate at
both sites. Moderate to fresh southwest winds will continue at
Pohnpei through Friday, easing slightly as we head into the weekend
to mostly moderate. A Small Craft Advisory remains in effect for the
coastal waters of Pohnpei through at least Thursday night and at
Kosrae through at least tonight. Combined seas of 5 to 7 feet will
continue for the next couple of days with seas consisting of a west
swell, a northeast swell, and a southerly swell. Locally choppy seas
will be possible at Pohnpei. Headlines were added at Pohnpei and
Kosrae for elevated surf possible along south-facing reefs at both
locations and also for west-facing reefs at Pohnpei.

Western Micronesia...
A ridge remains firmly in place over Palau and Yap regions, and is
still inducing some diffluent flow, leading to quiet conditions over
the a day or two. Island-induced showers and thunderstorms are
possible for Palau during the afternoons for the next few days.
Overall, a fairly dry pattern is expected to remain through Friday
night. Then, the monsoon disturbance, that is currently between Chuuk
Lagoon and Guam, is expected to move into the Philippine seas. This
is may produce showers, bring some much needed rain to Palau and Yap.

A monsoon disturbance, located northwest of Chuuk, is expected to
move in a general west-northwest direction and remain fairly
disorganized, however, the strengthening convergence along the
western and southern peripheries will be the focus of unsettled
weather for the region through the remainder of the week. As the
disturbance shifts west-northwestward, scattered showers and isolated
thunderstorms are expected to continue through Sunday at Chuuk.

Current altimetry data shows combined seas have remained relatively
stable at 2 to 4 feet near Palau and Yap, and 3 to 5 feet at Chuuk.
Benign marine conditions are expected to continue over the next
several days, with seas increasing to 4 to 6 feet by around Saturday
for Chuuk coastal waters due to an increase in south to southeast
swell. Light to gentle winds persist over the next several days with
an increase in gentle to moderate southwesterly winds at Chuuk
starting Wednesday.

&&

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

$$


Marianas/East and West Micronesia Update: Stanko
Marianas: Ogle
East Micronesia: Whisnant
West Micronesia: Bowsher