576
FXPQ50 PGUM 071908
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
508 AM ChST Tue Jul 8 2025

.Marianas Update...
Little change has been made to the forecast. Recent satellite
imagery, Doppler radar, and upper air sounding data draw better
support for lower PoPs the rest of today and tonight. In addition,
increased cloud cover and distance to nearby upper-level features
shows lesser support for thunderstorm development, so removed
thunderstorms from the forecast through tonight. The marine and surf
forecasts remain unchanged.

&&

.Eastern Micronesia Update...
An unsettled weather pattern remains across much of the Marshalls and
northern Kiribati due to the Intertropical Convergence Zone (ITCZ)
and a broad trough at its leading edge. Additionally, this feature is
linking up with diffluent upper-level flow to produce deep convection
and widespread cloudiness. Meanwhile, patchy clouds and showers are
seen to the west, over Pohnpei and Kosrae. As this trough slowly
weakens over the course of the day, a fragmented ITCZ pattern will
begin to extend farther westward, increasing showers for Pohnpei and
Kosrae in the latter half of the week. Only minor changes were made
to the forecast today. Numerous showers look to persist near Majuro
through the morning, decreasing to scattered in the afternoon.
Meanwhile, patchy showers across Kosrae are expected to increase to
scattered in the afternoon with the passage of a minor trough. For
Pohnpei, saw a slight decrease in precipitable water (PWATs) in the
sounding and CIMSS MIMIC TPW, which is supported by little to no
surface forcing observed in recent satellite imagery and model
trends. As such, lessened shower and thunderstorm potential through
tonight.

Scatterometry shows light to gentle trades across Pohnpei and Kosrae
and variable, gentle to moderate winds near Majuro. Buoy and
altimetry data indicate seas are 2 to 4 feet near Pohnpei and Kosrae,
and up to 6 feet near Majuro.

&&

.Western Micronesia Update...
Satellite imagery shows scattered showers developing across Palau and
Yap. This is within a light to gentle westerly flow that eventually
converges with a light to gentle trade pattern, generating widespread
showers over much of eastern Yap State. Meanwhile, relatively quiet
conditions are seen farther east over Chuuk Lagoon. Overall, no
major changes were made to the forecast overnight. Yap and Palau will
see a gradual increase in showers today, as the pattern shifts to
convergent southwesterly flow by tonight.

Buoy and altimetry show 1 to 3 foot seas over Palau and Yap, and 3
to 4 feet near Chuuk.

&&

.Prev discussion... /issued 654 PM ChST Mon Jul 7 2025/

Marianas Synopsis...
Satellite and radar imagery are showing mostly cloudy skies with
scattered showers, mainly over the coastal waters. Local buoys are
indicating seas of 2 to 3 feet.

Discussion...
The Marianas will remain sandwiched between a region of troughing and
monsoon flow to the north and west and ridging to the south and
east, with moist, converging southerly flow in-between over the
islands. Expect generally scattered showers (Probability of
Precipitation 30-40 percent) and isolated thunderstorms through the
period. An upper-level trough south of the Marianas sliding to the
west will bring divergence aloft and keep the shower and
thunderstorm potential on the higher end through Tuesday night.
Slightly more stable and drier conditions look to build in by
midweek as the surface ridge creeps towards the islands, forcing the
moist, converging flow off to our northwest. The troughing and moist
monsoon flow look to try and build back east towards the Marianas
over the weekend, with the shower and thunderstorm potential ticking
back up. Throughout the week, if enough clearing allows for
sufficient daytime heating and destabilization, we could see island-
effect showers and thunderstorms firing off as southerly winds will
generally be on the lighter side.

Marine/Surf...
Light to gentle southwesterlies will slowly pick up and become
gentle to moderate on Tuesday, then decrease slightly beginning
Wednesday and become light to gentle again by late week. Combined
seas of around 3 feet are expected for most of the week, possibly
increasing late week or the weekend as a west-northwest swell
emanating from a distant tropical disturbance to our northwest
arrives.

A low risk of rip currents is expected along all reefs for most of
the week. Surf and rip risk could rise toward the weekend along west
and north facing reefs, as the aforementioned swell arrives to the
region.

Eastern Micronesia...
The ITCZ is producing scattered to numerous showers over Kosrae and
RMI. Showers are expected to rebuild into the RMI overnight. A
trough east of RMI is what is expected to re-invigorate the showers
over the eastern half of the region. The models suggests the ITCZ
will flex southward. This will effect southern RMI and eventually
Kosrae. Scattered showers are expected to remain in the forecast
throughout the period for both RMI and Kosrae.

For Pohnpei, a trade-wind convergence zone has set up over the
northwestern corner of the region. This will keep scattered showers
in the forecast for the next 24 hours or so. Then a brief return to
a drier pattern will set up. The ITCZ is expected to arrive in
Pohnpei near midweek. This will bring showers back into the high-end
scattered showers and the peak of showers is expected Wednesday night
into Thursday morning before diminishing back to scattered.

Altimetry shows combined seas of 4 to 6 feet. Models suggest a
trade-wind swell will gradually build in the east that may bring seas
near Majuro up to 6 to 8 feet by the end of the week. Winds are
expected to remain light to moderate for much of the week. Majuro is
the exception for this as the winds here will build to gentle to
fresh by the weekend.

Western Micronesia...
Winds in Western Micronesia will be light to gentle this week. At
Chuuk they will be light to gentle from the east, with combined seas
of 3 to 5 feet. Showers should be isolated through Wednesday, then
could fill in Wednesday night and remain through Saturday. At Yap,
the winds will be light to gentle from west, gradually turning
toward the west-southwest which is delaying everyone else. Koror
Palau has weather similar to Yap, light to gentle west to southwest
winds, isolated showers tonight, then gradually filling in Tuesday
for the rest of the week.

Marine conditions will be benign other than the chance of thunder. Be
on the lookout for lightning, stay below deck for 30 minutes after
the latest lightning strike, and you will know you`re safe.

&&

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

$$

Marianas Update: Montvila
East/West Micronesia Update: Cruz
Marianas: Stanko
East Micronesia: Bowsher
West Micronesia: Slagle