506
FXPQ50 PGUM 032002
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
602 AM ChST Mon Aug 4 2025


.Marianas Update...
Overall, only minor edits were needed to the forecast, namely in the
marine sections. The west-northwest swell has broken down a little
quicker than anticipated, because of this, the north and west surfs
where dropped by a foot. The surf along east facing reefs were held
on to though, due to the trade-wind swell remain around 3 to to 5
feet.

The TUTT cells has moved far enough west that the cell is no longer
producing pop-up thunderstorms for Tinian and Saipan. Showers are
expected to remain scattered today due a few factors. In the morning
hours, speed convergence will produce small quick moving showers,
and as the day progress a trough will move in and bring in showers
that are a little more developed.

&&

.Eastern Micronesia Update...
Satellite imagery this morning shows a fairly quiet and dry pattern
across the region with a minor trade-wind trough in the Marshall
Islands producing spotty showers. Very little was changed in the
forecast as this drier pattern is expected to continue through most
of the week. Models continue to show a weak band of convergence
moving through the Majuro and Kosrae around Thursday, bringing a
brief period of scattered showers to both islands.

A relatively benign marine forecast will continue across the region,
driven by a fairly typical trade swell. Pohnpei and Kosrae will see
gentle to moderate winds through Tuesday, becoming light to gentle,
with combined seas of 3 to 4 feet. Majuro will see light to gentle
winds and combined seas of 4 to 5 feet through the week.

&&

.Western Micronesia Update...
Two broad troughs are moving through the region, one north-northwest
of Yap and the other moving through Chuuk State. The trough near Yap
had a weak circulation embedded in it yesterday, but this circulation
is difficult to distinguish in the latest scatterometer data. This
trough is also currently producing scattered showers and isolated
thunderstorms mainly north of Yap this morning, so delayed scattered
showers for both Yap and Palau to this afternoon, as weak convergent
flow to the east of Yap and Palau is expected to help trigger
scattered showers near the islands later today. The trough near Chuuk
is producing scattered showers and isolated thunderstorms, but is
slowly drifting west so this should allow showers to decrease to
isolated this afternoon while also decreasing the potential for
thunderstorms. As the trough near Chuuk continues westward towards
Palau and Yap, periods of scattered showers and thunderstorms will
continue for Palau and Yap into the middle of the week, and then
decreasing near the end of the week. For Chuuk, model guidance
suggests weak convergent flow will develop east of the trough which
will continue to support periods of scattered showers over the next
few days and potentially into the end of the week.

Winds are expected to remain light to gentle, with some variability
in direction as the troughs move through the region. Seas around
Palau and Yap will remain around 2 to 3 feet and 3 to 4 ft at Chuuk,
where the trade swell is slightly stronger.

&&

.Prev discussion... /issued 411 PM ChST Sun Aug 3 2025/

Marianas Synopsis...
Satellite imagery shows partly cloudy skies across the Marianas
while Doppler Radar shows isolated showers. Altimetry and Buoy data
shows combined seas between 4 to 6 feet.

Discussion...
Quiet conditions are seen across the Marianas this afternoon.
However, scattered showers are seen just outside Guam`s coastal
waters and should enter the region over the next couple of hours.
Scattered showers remained in the forecast for tonight, though radar
trends suggest there could be an opportunity for higher shower
coverage across Guam. After a brief lull on Monday, shower activity
looks to remain scattered due to passing trade-wind convergence,
surface troughs, and weak circulations. PoPs may need to be
increased Tuesday and Wednesday as both the GFS and ECMWF show a
monsoon-like pattern with westerly winds just to our west and
southeasterly winds just to our east, leading to surface convergence
over the Marianas. For now, kept PoPs at 30%, but high end scattered
to low end numerous showers may be necessary with future forecasts.

Marine...
Combined seas look to remain benign the next several days with 4 to
6 foot seas falling to 3 to 5 feet late tonight into Monday. The
primary westerly swell will diminish late tonight, becoming a
secondary swell to the east swell by Monday night. A moderate risk
for rip currents will continue across west, north, and east facing
reefs through Monday before decreasing to low on west and north
facing reefs Monday night.

Eastern Micronesia...
The Inter-Tropical Convergence Zone (ITCZ) has dissipated across
eastern Micronesia. With only weak trade-wind troughs expected to
move through the region over the next few days, a dry trade-wind
pattern looks likely for the most of the week at Kosrae and Majuro,
and for the entire week at Pohnpei. For Majuro and Kosrae, a weak
transient band of convergence looks to move through the area around
Thursday, bringing a brief period of scattered showers to both
locations as the band moves through.

A relatively benign marine forecast will continue across the region.
Pohnpei and Kosrae will see gentle to moderate winds through Tuesday,
becoming light to gentle, with combined seas of 3 to 4 feet. Majuro
will see light to gentle winds and combined seas of 4 to 5 feet
through the week.

Western Micronesia...
Yap has a weak circulation passing not too far to the north. This
will bring some scattered showers over the next few days, and the
showers might even dip down toward Koror, Palau at times. Chuuk has a
similar feature passing to their south, and could see some scattered
showers the next few days. Specifically, Koror could see isolated
showers tonight become scattered Monday, and these could last through
Thursday, becoming isolated again by Friday. Yap could see scattered
showers that might last through Thursday, becoming isolated by
Friday. And Chuuk could see scattered showers that might last through
Tuesday, becoming isolated by Tuesday night, then they could become
scattered again during the last half of the week.

For the Chuuk marine forecast, winds will be capped at 10 knots. Seas
will be in the 3 to 4 foot range, leading to benign weather
conditions expected. In the Yap Waters, winds will also be capped at
10 knots. Seas will be around 3 feet, also leading to benign weather
conditions expected. Near the Koror, Palau Waters, winds could reach
10 knots Tuesday and Tuesday night, but will mostly be capped around
5 knots. Seas will range from 2 to 3 feet, and it`s difficult to see
how you could get more benign than that.

&&

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

$$

Marianas Update: Bowsher
East/West Micronesia Update: Schank
Marianas: Williams
East Micronesia: Kleeschulte
West Micronesia: Stanko