976
FXPQ50 PGUM 021954
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
554 AM ChST Wed Sep 3 2025

.Marianas Update...
Guam Doppler weather radar shows scattered showers moving through the
Marianas Waters. The inherited forecast had this well covered, with
isolated showers farther north. Just bumped the PoP`s from 30 to 40
with the showers now appearing on radar. No other changes were
needed.

&&

.Tropical Systems...
Invest Area 95W is located near 20N131E. It is currently the subject
of a Tropical Cyclone Formation Alert from the Joint Typhoon Warning
Center. This means the chance of it developing into a Tropical
Depression within the next 24 hours is high. In the not too distant
future, it is also quite likely to move westward out of the WFO Guam
Area of Responsibility. In the meantime, for further updates, please
refer to future issuances of the WFO Guam Area Forecast Discussion,
AFDGUM, under WMO header FXPQ50 PGUM, the WFO Guam Tropical Weather
Discussion, TWDPQ, under WMO header AXPQ20 PGUM, and the Tropical
Significant Weather Advisory from the Joint Typhoon Warning Center
under WMO header ABPW10 PGTW.

&&

.Eastern Micronesia Update...
The forecast for Eastern Micronesia was in fine shape, just nudged
the PoP`s for Majuro today from 30 to 40 as the showers are moving in
on satellite. Analysis shows the showers are being caused by a
trade-wind trough just east of Majuro. The only other change was to
decrease clouds at Kosrae, making it mostly sunny instead of partly
sunny. No changes were made at Pohnpei.

&&

.Western Micronesia Update...
The forecast for Western Micronesia was in good shape. Most of the
showers are passing south of Chuuk, so isolated looks good for them
today. It will remain fairly cloudy though, so partly sunny also
looked good. There are showers fairly near both Yap and Palau, so
retained scattered showers there for today.

&&

.Prev discussion... /issued 702 PM ChST Tue Sep 2 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,
0.80 inches of rain has fallen at the airport.

Discussion...
A trough is moving towards the Marianas. This will bring scattered to
numerous showers and isolated thunderstorms to the region through
the middle of the week. Radar indicates that the showers associated
with this trough in the nearby waters are diminishing. However,
showers are expected to pick back up overnight. Model guidance
suggests the peak of the showers will be tonight 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 between 3 and 4
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 east facing reefs. Surf is expected to fall a foot by
Thursday. Surf is expected to remain below hazardous levels through
the rest of the week. There is also a moderate risk if lightning
through Wednesday.

Eastern Micronesia...
A surface trough stretches from Chuuk to north of Pohnpei this
afternoon, with streamlines and MIMIC water vapor imagery suggesting
a new surface trough is trying to form between Pohnpei and Kosrae, as
MIMIC water values increase slightly to near 2.5 inches, with some
mild "bending" in the streamline analysis. This is likely due to a
ITCZ (Inter-Tropical Convergence Zone) fragment that has surged
across the Date Line as expected, accompanied by a lead surface
trough that`s located east of Majuro. However, as the ITCZ
temporarily strengthens, moisture flux westward is occurring, helping
to explain the genesis of the Pohnpei/Kosrae trough. This trough
then gets overtaken by the Majuro trough by late Thursday night.

What this means is there`s an increasing rainfall potential from
east to west over the next few days as these features interact as
they pass through Eastern Micronesia on their westward journey.
Following the Majuro trough passage, rainfall coverage is anticipated
to drop back to isolated shower coverage, with the best rainfall
potential being Wednesday and Wednesday night at Majuro...Wednesday
night and Thursday at Kosrae...and Thursday and Thursday night at
Pohnpei.

As for marine conditions, mainly light to gentle winds will prevail,
but they could briefly become moderate from time to time. Seas of 3
to 5 feet will build a foot into the 4 to 6 foot range Thursday
following trough passage, continuing through the weekend and into
next week.

Western Micronesia...
A broad surface trough continues to bring patchy showers and some
thunderstorms to Palau and Yap overnight (with gustier heavy showers
at Yap), followed by another drier cycle to last for the rest of the
week. At Chuuk, a mostly quiet pattern with gentle to moderate
easterlies is still expected to persist through Thursday night,
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 3 to 4 feet near Palau and Yap are expected to
remain as such the next few days, as 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/Tropical Update: Stanko
Marianas: Bowsher
East Micronesia: Doll
West Micronesia: Montvila