199
FXPQ50 PGUM 222002
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
602 AM ChST Sat Aug 23 2025

.Marianas Update...
The Marianas have partly sunny/mostly cloudy skies with scattered
showers. These are expected to continue for the next several days as
an overall convergent pattern remains settled in. Looks like a fairly
wet week in store. The inherited forecast had this well covered so no
updates were needed.

&&

.Marine...
Combined seas are 2 to 3 feet on the buoys currently. They will
remain near these heights through Monday, then increase by Tuesday.
The increase will likely be just enough to raise the rip current risk
back to moderate along east facing reefs.

&&

.Eastern Micronesia Update...
Pohnpei is drier today, but looks to have increasing showers tonight.
Kosrae is having scattered showers today, and the models suggest more
will brew for tonight. Majuro has plenty of scattered showers to the
east which look like they will be moving in. These were all well
handled in the previous forecast package so no changes were made.

For winds, Pohnpei will have 5 to 10 knots through the period,
Kosrae will have 5 to 10 knots through the period, and Majuro will
have 5 to 15 knots. For seas, Pohnpei will have 3 to 5 feet through
Wednesday. For Kosrae, seas will be 3 to 5 feet for most of the week,
but 4 to 6 feet for Sunday night, then become slightly smaller again.
For Majuro, seas will be 4 to 6 feet for most of the period due to
increased wind waves.

&&

.Western Micronesia Update...
Koror has showers closing in on satellite, so numerous today tapering
to scattered tonight looks good there. Yap also has showers moving
in, they are less active than at Koror however, so scattered for
both today and tonight looks fine. Chuuk looks likely to have a
glancing blow from some showers today, then the models show
increasing activity near them tonight. It doesn`t show up on
satellite yet, so we`ll be watching, but until the new package we`ll
go ahead and trust the models.

Palau, Yap and Chuuk will all have winds of 5 to 10 knots through
Wednesday. Also, all 3 will have seas of 2 to 4 feet for the entire
period, although the 2 footers will be concentrated mostly near Koror
Palau.

&&

.Prev discussion... /issued 553 PM ChST Fri Aug 22 2025/

Marianas Synopsis...
Radar and satellite imagery shows showers dissipating over the
Marianas. Altimetry and buoys show combined seas of 2 to 4 feet.
Winds are gentle to moderate. Today had a wet morning, 0.85 inches of
rain had fallen by this afternoon.

Discussion...
A slow-moving broad trough is producing showers and thunderstorms for
the Marianas and nearby waters and is expected to continue through
tonight and Saturday. This pattern is expected to continue through
the forecast period, due to more trade-wind troughs and upper-level
divergence. Scattered showers and isolated thunderstorms should be
expected for the next few days. Around Monday, a short lull is
anticipated, however, this lull appears to last for about 12 to 24
hours. Then showers may return for the rest of the forecast period.

Marine...
Combined seas are anticipated to gradually rise by about a foot by
the beginning of the work week. This will cause the surf along east
facing reefs to meet the threshold of 5 feet. This will force the
risk of rip currents to become moderate along east facing reefs.

Eastern Micronesia...
A couple of trade-wind troughs are moving through eastern Micronesia
this afternoon. The first is moving through just south of Pohnpei and
is expected to increase convection there, though most of the showers
look to remain south of the waters, so maintained isolated showers
for now. The next one is found to the east of Kosrae. This trough
looks to bring scattered showers back to Kosrae by Saturday morning.
Th last trough is seen to the east of Majuro. This trough is
interacting with a weak fragment of the Inter-Tropical Convergence
Zone (ITCZ) to bring scattered showers and isolated thunderstorms to
Majuro through tonight. later in the weekend, model guidance favors a
strengthening ITCZ for the region. This would result in increased
convection across the region. Showers will begin to increase over the
weekend, peaking early next week. Due to uncertainty with the
location of the developing ITCZ, POPs (Probability of Precipitation)
were kept at or below 50%. This could change over the coming week.

The marine forecast remains relatively unchanged. Expect combined
seas to remain between 3 and 5 feet across the region. Winds are
expected to be light to gentle for Pohnpei and Kosrae, with
occasional moderate winds at Majuro into the beginning of next week,
becoming light to gentle by Tuesday.

Western Micronesia...
A monsoon trough now extends eastward into far western Micronesia,
passing through a weak, oblong circulation which has taken shape
near Palau and Yap. Gentle to moderate westerlies now prevail across
much of the Republic of Palau, south of the monsoon trough axis
which extends east-southeast from around 10N130E to around 6N144E,
passing just north of Koror, south of Yap Proper, to end around
Eauripik in Yap State. The embedded circulation is poorly organized
and widespread cloud cover makes the center difficult to pinpoint.
This morning`s scatterometry places the circulation center just over
western Palau waters, but visible satellite this afternoon suggests
it is somewhere just northeast of Koror, around 8N136E. Convection
is loosely focused along the eastern and northern flanks of the
circulation, with lines of heavy showers and thunderstorms mainly
seen to the north and northwest of Yap, and west of Ngulu.

The monsoon trough and embedded features will maintain at least
scattered showers for Palau and Yap through the weekend, but for now
much of the convection is focused to the north of coastal waters, so
kept Probability of Precipitation (PoP) for these locations at 50%
for tonight, increasing to 60% on Saturday for Palau as the
circulation meanders west through the area. After tonight, showers
look to diminish slightly for Yap through the rest of the weekend as
the disturbance moves away. The monsoon trough looks to stick around
into early next week as another weak disturbance forms to the west of
Chuuk, gradually shifting west towards Yap and Palau through mid-
week. This will bring periods of scattered showers to Chuuk through
at least the first half of next week, but otherwise Chuuk should
enjoy relatively quieter conditions for the next day or so.

Little change was made to the marine forecast. Altimetry data shows
benign seas across the region, with combined seas of around 2 to 4
feet. Seas look to increase by a foot or two early next week mainly
across Palau waters, as a south to southwest swell sets up in
response to a developing monsoon-like pattern. However, marine
hazards are not expected at this time.

&&

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

$$

Marianas: Stanko