422
FXPQ50 PGUM 011946
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
546 AM ChST Tue Sep 2 2025

.Marianas Update...
Marianas forecast was in good shape, with little change in
philosophy. Only tweak was, with showers on radar bearing down on the
islands, raised the PoP for today from 40 to 50. Combined seas are
still around 4 feet. Did mention occasional gusts to 25 knots in
showers for the coastal, that was the only other change.

&&

.Eastern Micronesia Update...
Eastern Micronesia continues to have little in the way of deep
convection except north of 12N. A massive shield of debris
cloudiness includes both Pohnpei at its western edge and Kosrae at
its southern edge. It no longer includes Majuro which has broken free
from the eastern edge. This was expected, so there`s little change
for Majuro. Just increased the clouds at Kosrae, and little change at
Pohnpei.

&&

.Western Micronesia Update...
The main mass of clouds and showers is between Yap and Chuuk, and
will remain so today. Therefore the only needed update was to delay
the onset of scattered showers at Yap and Palau. To this end, reduced
clouds at Chuuk, and reduced clouds and showers at both Yap and
Palau. This took both of them from scattered showers to isolated.
Everything else was fine, including seas and winds, so no other
changes were needed.

&&

.Prev discussion... /issued 639 PM ChST Mon Sep 1 2025/

Marianas Synopsis...
Satellite imagery shows mostly cloudy skies, while the radar shows
isolated showers. Ritidian buoy shows sea heights of near 3 feet.
Winds are gentle to moderate with a few fresh gusts. So far today, a
little above 2 inches of rain has fallen at the airport.

Discussion...
A trough is moving towards the Marianas. This will bring scattered
showers and isolated thunderstorms to the region through the middle
of the week. Model guidance suggests the peak of the showers will be
around Tuesday night into early Wednesday morning. Once this trough
passes a ridge is anticipated to build in, bringing in some drier
more pleasant weather.

Marine...
Combined seas of 3 to 5 feet are expected to fall to around 3 feet
across the region by the end of the week, due to the weakening of
the trade winds and swell. There is a moderate risk of rip currents
along south facing reefs. Surf is expected to fall by about a foot by
Tuesday. Surf is expected to remain low through the rest of the
week. There is also a moderate risk if lightning through Wednesday.

Eastern Micronesia...
A surface trough currently passing through Pohnpei, will continue to
bring scattered showers and perhaps a thunderstorm to the region
tonight, moving off to the west Tuesday when isolated showers
return, with Kosrae and Majuro only seeing isolated showers through
Tuesday night as well. Then, a new ITCZ (Inter-Tropical Convergence
Zone) fragment east of the Date Line reaches Kosrae and Majuro by
late Wednesday, increasing cloud cover and rainfall potential.

Then for Thursday and Friday, Pohnpei begins to see increased
rainfall potential as the fragment moves west, temporarily leaving
Kosrae and Majuro with just isolated showers. That`s short lived
though as yet another surface trough/ITCZ fragment crosses the Date
Line and increasing your rainfall potential at Kosrae and Majuro
Friday night into Saturday, while Pohnpei dries out.

As for marine conditions, seas of 3 to 5 feet will build into the 4
to 6 foot range Wednesday into Thursday, dropping a foot by Saturday.
Mainly light to gentle winds will prevail this week.

Western Micronesia...
A subtropical ridge has settled across Palau and Yap, allowing winds
and showers to briefly diminish through at least Tuesday. After, a
broad surface trough is expected to bring back patchy showers and
some thunderstorms around midweek, followed by another drier cycle to
last for the rest of the week. At Chuuk, a mostly quiet pattern with
gentle to moderate easterlies will prevail through Thursday, followed
by a trade-wind surge moving in from the east, bringing elevated
shower and thunderstorm potential towards the end of the week.

Combined seas of 4 to 6 feet near Palau and Yap are expected to
decrease 2 to 3 feet over the coming days, as southwesterly winds
and swell decrease and trade swell remains fairly weak. Combined seas
of 3 to 5 feet near Chuuk are expected to remain as such for much of
the forecast period, comprised mainly of an easterly swell.

&&

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

$$


Marianas/East and West Micronesia Update: Stanko
Marianas: Bowsher
East Micronesia: Doll
West Micronesia: Montvila