952
FXPQ50 PGUM 081939
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
539 AM ChST Wed Sep 9 2026

.Marianas Update...
Satellite and radar show the Marianas are mostly cloudy with
scattered showers, and lightning data adds isolated thunderstorms. In
the next few hours the initial wave will push through, and weather
could improve. There`s a lot of randomly scattered stuff behind it
though, so we will still have something. Maybe low end scattered
showers with isolated thunderstorms, for the next couple of days.

&&

.Eastern Micronesia Update...
Eastern Micronesia is looking wet thanks to the monsoon trough... and
it is! Windy too, in places at least. So we have small craft
advisories in Pohnpei and Kosrae, and we`re only a little short of
one in Majuro. This is making marine conditions quite challenging, a
special (perhaps even just one-time) forecast is out for the atoll of
Namorik where a supply ship got caught by surprise. They will either
have to wait it out there or try to get over into the lee of Jaluit.

&&

.Western Micronesia Update...
At least according to my Decoded Synoptic Viewer, Koror Palau has
just notched in a 13th day with no measurable rainfall. They`re
already at D-0 in the USA Drought Monitor, and could be headed for
D-1 later this week, because as we saw, things are starting to look
pretty grim. Yap is only a little better with just 0.16 inches
measured in the last 10 days. At least Chuuk got a little rainfall...
the emphasis is on little. But, it`s a tenth of an inch less they`ll
have to scrimp from somewhere else later.

&&

.Prev discussion... /issued 610 PM ChST Tue Sep 8 2026/

Marianas Synopsis...
Visible satellite and radar imagery depicts isolated showers and
towering convection entering Saipan and Tinian coastal waters,
partly cloudy skies across Rota, and scattered island-effect showers
over southern Guam and adjacent coastal waters. Altimetry data
indicates combined seas of 3 to 5 ft.

Discussion...
A trade-wind trough oriented from the northwest to the southeast will
bring a brief wetter period of scattered showers and isolated
thunderstorms tonight through Wednesday. Due to its orientation and
northeasterly motion, Saipan and Tinian will see these showers
first, with the onset this evening for their coastal waters, and
after midnight for these islands. Remnant island-effect showers are
ongoing for southwestern Guam and adjacent coastal waters, so a
thunderstorm or two should not be ruled out from now until shortly
after sunset. Then, isolated thunderstorms will become a concern for
Guam and Rota after midnight, but the increase in shower coverage is
not expected until Wednesday morning. The duration of these showers
heavily depends on the longevity of this feature, however, model
guidance indicates a return to drier weather starting Wednesday
afternoon for Saipan and Tinian, and Wednesday evening for Guam and
Rota. This along with slightly different wind directions out of the
north and northeast supported a split zone, however, a return to one
zone wouldn`t be out of the question over these next few forecast
issuances. Then, a potentially broad circulation may impact the
region around Thursday, so shower coverage tops out at 30 percent,
with thunderstorm potential most likely added in the coming shifts,
but winds may be light and variable should the circulation remain
weak. This situation will continue to be refined as confidence
increases naturally with time. A return to drier weather is possible
in the latter half of the week with isolated light showers (10%
chance) included.

Marine...
Benign seas and light to gentle winds varying out of the north to
east are expected throughout the week. The zones remained split to
account for slight differences in wind directions and timing of
showers. A northeasterly trade swell will build in starting tonight,
eventually becoming the dominant pattern once the westerly swell
tapers down. There is a moderate risk of rip currents along west
facing reefs tonight, joined by north and east facing reefs on
Wednesday.

Eastern Micronesia...
The monsoon surge is now affecting eastern Micronesia, with winds
increasing across Kosrae and showing strong signs of increasing over
Pohnpei by early Wednesday morning. The latest satellite data shows
strong cumulus cloud lines moving rapidly through Kosrae. Convection
looks to increase over Pohnpei and Kosrae through the night, with
scattered showers expected at both locations by Wednesday morning.
This looks to be the onset of a wet, unsettled pattern across both
locations that looks to continue through the weekend. POPs
(Probability of Precipitation) look to increase to around the 60
percent range Thursday night at Pohnpei and Friday at Kosrae and
continue at that level through the weekend. Models are indicating the
possibility of heavy rainfall potential, though confidence remains
low at this time. Regardless, showers and thunderstorms are on tap
for both locations through the weekend.

For Majuro, scattered showers are now in place across the waters
just north of the atoll and only look to increase through the
evening. POPs could reach the 60 percent range there as well
Wednesday night into Thursday as a weaker surge affects the
Marshalls, and again during the weekend.

For the marine forecast, winds have increased across Kosrae this
afternoon and look to increase across Pohnpei by Wednesday morning.
Fresh to strong monsoon winds in the surge are expected across
Pohnpei with moderate to fresh winds with frequent strong gusts
across Kosrae. The surge looks to weaken by Thursday morning at
Kosrae and by Friday morning at Pohnpei. Based on winds, a Small
Craft Advisory was issued for Kosrae beginning this afternoon and
for Pohnpei beginning early Thursday morning. Seas are not going to
be that impressive, but could reach as high as 7 to 8 feet at
Pohnpei, making for choppy seas in the open waters. For Kosrae, seas
are expected to be at or below 7 feet. Majuro looks to see gentle
winds increasing to moderate to fresh around Thursday afternoon.

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 several few days. During this period of drier weather, haze
sourced from distant wildfires in Indonesia are expected to continue
across Palau and Yap. 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 Sunday.

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.

Latest altimetry data shows combined seas have remain steady 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 around Thursday 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: Mesa
East Micronesia: Kleeschulte
West Micronesia: Bowsher