953
FXPQ50 PGUM 291809
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
409 AM ChST Sat Aug 30 2025

.Marianas Update...
A wet pattern is still on tap for the Marianas this weekend. However,
the trough that is expected to bring numerous showers to the islands
remains a bit too far south of Guam. Therefore, lower POPs
(Probability of Precipitation) to 50% for today. Numerous showers
with isolated thunderstorms and locally heavy rainfall is still
possible this evening as the trough approaches. Otherwise, no changes
made to the previous forecast.

&&

.Tropical Systems Update...
Invest 94W remains over Chuuk State and is seen as a broad area of
troughing across the region. Neither satellite nor ASCAT analysis
show any hint of a circulation with Invest 94W. This system will be
monitored closely as it drifts north over the coming days.

Invest 95W remains a broad, weak circulation north of Palau, centered
near 10N134E. Latest model guidance shows little change with 95W over
the next couple of days. 95W will be monitored closely for any
indication of development.

&&

.Eastern Micronesia Update...
The ITCZ has pretty much dissipated across the region. This has
allowed convection to decrease to isolated at Majuro, with POPs
dropping to low-end scattered for Pohnpei and Kosrae. Several trade-
wind troughs are still expected to move through the region,
increasing convection across eastern Micronesia again this evening.
No changes were made to the remainder of the forecast.

&&

.Western Micronesia Update...
Invest 94W has weakened and drifted northwest, allowing convection to
subside over Weno this morning. However, a trade-wind trough will
approach from the east, bringing increased showers back to Weno this
afternoon.

For Yap and Palau, a well developed monsoon pattern will continue
across the region for the next several days. Convection has decreased
across Palau for now, but a surge in the monsoon flow will bring
numerous showers and isolated thunderstorms back to the Republic this
afternoon. For Yap, numerous showers and isolated thunderstorms will
continue through the day. Moderate to fresh winds are expected at
both locations for the next day or so.

No other changes were made to the remainder of the forecast.

&&

.Prev discussion... /issued 657 PM ChST Fri Aug 29 2025/

Marianas Synopsis...
Gentle to moderate easterlies prevail across the region, as satellite
imagery and Doppler radar indicate a few lines of fast-moving showers
entering Guam`s southern waters. The buoys indicate seas are 5 to 6
feet.

Discussion...
A broad trough extending from a developing tropical disturbance in
western Micronesia, is expected to bring increasing showers and
thunderstorms over the next few days. On-and-off showers overnight,
are expected to continue to increase through Saturday, with heavy
showers and thunderstorms along with gusty winds likely coming into
Saturday night. As the aforementioned disturbance moves toward the
Philippines and drags said trough along with it, a minor ridge will
form in its wake over the Marianas, diminishing shower and
thunderstorm coverage considerably. Even so, showers are expected to
remain low-end scattered around Labor Day. Patchy showers are to
return to the region for much of next week as more troughs make their
way across.

Marine...
Combined seas of 5 to 7 feet are expected to taper down a foot over
the weekend, to then diminish another 2 feet by midweek as trade
swell and wind waves diminish. A moderate risk of rip currents is
expected along north and east facing reefs for at least the next
several days. As trade swell and wind waves decrease, surf will
diminish enough along all reefs to allow the rip current risk to drop
to moderate along north facing reefs around midweek.

Tropical Systems...
The Joint Typhoon Warning Center has open two broad invest areas
within the region this afternoon. The first is Invest 94W, located
west of Chuuk Lagoon, centered near 7N149E, and is within the broad
troughing that is across Chuuk State and was originally anchored to
a weak circulation south of Chuuk. The second is Invest 95W, located
west of Palau near 10N131E, focused on the monsoon trough and pattern
extending across Palau and Yap. Scatterometer data from this morning
shows a sharp trough axis across both invest areas, but no distinct
surface circulation can be found within either area. The invest areas
are being used to monitor the potential for a circulations to
develop within the western or eastern side of trough axis as the
monsoon pattern evolves and starts to lift northward over the next
few days. In the short-term, periods of numerous locally heavy
showers creating gusty winds and choppy seas are expected across
Palau and Yap, and extending up towards the Marianas this weekend.
Currently the potential for 94W or 95W to develop into a significant
tropical cyclone over the next 24 hours is very low. Continue to
monitor the forecast for the latest trends and information as both
the Joint Typhoon Warning Center and the National Weather Service
continues to monitor the region.

Eastern Micronesia...
Showers have diminished slightly over the region since yesterday as
the Intertropical Convergence Zone (ITCZ) has fragmented into a
series of surface troughs. One such trough extends west-southwest
across the northern Marshall Islands to near Pohnpei, and scattered
to numerous showers are present throughout, with isolated
thunderstorms just north of the RMI where upper-level divergence is
enhanced. Scattered showers are also seen further south near Pohnpei
and Kosrae, in areas of shallow troughing and weak convergence in the
east-southeast trades. Between the Date Line and the RMI, numerous
showers are building just over and east of Majuro, along a
reorganizing ITCZ fragment. Showers look to increase overnight for
Pohnpei as convergence builds along the east side of the broad
trough and Invest 94W near Chuuk, with additional shallow troughs
maintaining a fairly wet pattern there through Sunday. This will be
followed by a drier pattern across much of eastern Micronesia through
early next week as a more zonal, stable regime sets up. Numerous
showers will continue for Majuro overnight with a gradual decrease
through the early morning as the ITCZ fragment overhead lifts north
and weakens, with gradually diminishing scattered showers through the
weekend.

A High Surf Advisory has been issued for east facing reefs of Kosrae
through 6 AM Saturday morning. Recent buoy data shows combined seas
around 5 to 7 feet, comprised mainly of the east-southeast trade
swell, sufficient to generate hazardous surf of 8 feet. However, seas
have been diminishing this afternoon, and surf along east reefs is
expected to relax below hazardous levels by tomorrow morning.
Elsewhere, buoy and altimetry data indicate seas of around 4 to 6
feet near Majuro and 3 to 5 feet near Pohnpei. Seas are expected to
fall by a foot or so through early next week as the trade swell
relaxes. Around Tuesday, a light northerly swell looks to enter the
region, emanating from a robust mid-latitude system crossing the
north Pacific.

Western Micronesia...
Latest satellite imagery shows numerous locally heavy showers and
isolated thunderstorms across Palau and Yap this evening, while
showers look to be on the downtrend at Chuuk as the heavier gusty
showers earlier today have pulled off to the west. Palau and Yap are
expected to see a slight down trend in showers overnight as the
atmosphere briefly stabilizes, before increasing again Saturday and
Saturday night, with locally heavy rainfall and gusty winds around 30
kt expected in heavier showers and thunderstorms, as the monsoon
pattern continues to evolve and then lifts northward. The Joint
Typhoon Warning Center has opened Invests 94W and 95W along the
western and eastern half of the monsoon pattern that extends across
the region to monitor the potential for circulations to develop and
strengthen within the pattern over the next few days. For more info,
please see the Tropical Systems section above. Seas and surf are
expected to be elevated and choppy, driven by gusty winds, and
peaking at around 7 or 8 feet, below the hazardous levels of 10 feet
and 9 feet, respectively. As the monsoon trough lifts north of Palau
and Yap around Sunday night or Monday, gusty winds, seas, and surf
are expected to decrease as models show a weak ridge of high pressure
building into the region, which would also lead to a reduction in
the intensity and coverage of showers.

For Chuuk, the core of heavy, gusty showers look to have pulled away
to the west, but additional surface troughs moving through eastern
Micronesia will continue to produce periods of scattered showers and
isolated thunderstorms through at least Saturday night. Then models
show a weak ridge of high pressure developing between Chuuk and the
Marianas, which should lead to a decrease in showers, while also
leading to lighter winds. This pattern is expected to be short-live
as the ridge is expected to shift towards Palau and Yap, with
additional troughs moving into the region by the middle of the week.
Seas at Chuuk will be around 4 to 6 feet through Saturday night,
driven mainly by the slight increase in the easterly swell, then seas
are expected to decrease 1 to 2 feet early next week as the east
swell subsides.

&&

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

$$

Marianas/East Micronesia/West Micronesia Updates: Kleeschulte
Marianas: Montvila
East Micronesia: DeCou
West Micronesia/Tropical: Schank