744
FXPQ50 PGUM 060105
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
1105 AM ChST Wed Aug 6 2025

.Marianas Update...
Only minor changes were needed overnight. The most notable change
was the slight uptick in the PoP`s (probability of precipitation) for
Guam tonight. Models suggest that Guam will be on the border between
isolated and scattered showers tonight. The other change was the
removal of the secondary swell for today and tonight. While it is
still measurable it is negligible. Combined seas have also dropped a
bit allowing the surf and risk to rip current to drop a category to
below 5 feet on all reefs and low risk. Seas are expected to remain
benign through the rest of the week.

&&

.Eastern Micronesia Update...
Only a few minor changes needed in Eastern Micronesia for today.
Moved the scattered showers in Kosrae up to this afternoon instead of
tonight, and reduced cloudiness and thunderstorms a little. This had
the effect of removing thunderstorms from the forecasts for the main
3 islands. Some thunderstorms are still expected, just not at the
main islands of Pohnpei, Kosrae or Majuro.

For the Majuro marine forecast, winds will be 5 to 10 knots through
the weekend. Seas will be 4 to 5 feet through Friday, then diminish
to between 3 and 4 feet for the weekend.

Within the Kosrae Waters, winds will be 10 to 15 knots today, then 5
to 10 knots through the weekend. Seas will be 4 to 5 feet through
Thursday night, then diminish to between 3 and 4 feet Friday.

The Pohnpei Waters will feature winds of 5 to 10 knots and seas of 3
to 4 feet through the period. Weather wise at least, it sounds like
fairly smooth marine travel in Eastern Micronesia. The GEFSwave
probabilistic Small Craft Advisory guidance is flat zero for the rest
of this week, a few minimal spots removed from the coastal waters for
next week, and even the third week when it does hit Kosrae and Majuro
Waters, it`s only a 3% change, pretty much negligible.

&&

.Western Micronesia Update...
Only minor updates in Western Micronesia also. Raised the PoP`s a bit
for today and tonight in Yap and Koror, Palau as a trough and line of
showers passes through. Slightly reduced the PoP`s at Chuuk for
Thursday. Slightly increased the PoP`s at Koror, Palau for tonight.

For the Chuuk marine forecast, winds of 10 to 15 knots today will
become 5 to 10 knots through the weekend. Seas will be 3 to 4 feet
through Friday then could diminish to between 2 and 3 feet for the
weekend.

Within the Yap Waters, winds will be 5 to 10 knots through the
weekend. Seas will be 2 to 3 feet through Saturday, then could build
to between 3 and 4 feet Sunday.

The Koror, Palau Waters will feature winds of 5 to 10 knots through
the weekend. Seas will be 2 to 3 feet through the weekend, possibly
reaching a minimum of just 2 feet on Friday. The GEFSwave
probabilistic Small Craft Advisory guidance suggests zero chance
through the 14th of August. Even after that, the maximum was 6%
anywhere, and it never got above 3% in any of the coastal waters of
Chuuk, Yap, or Koror, Palau.

&&

.Prev discussion... /issued 553 PM ChST Tue Aug 5 2025/

Marianas Synopsis...
A band of showers and thunderstorms has been very slowly building
over eastern Marianas coastal waters this afternoon, with stratified
remnants and mostly cloudy skies seen over Guam and Rota. Latest
visible satellite and radar show the main band of showers is just
east of Saipan and Tinian, with outflow boundaries sweeping north
through eastern Saipan waters. Buoy and altimetry data show combined
seas of 2 to 4 feet.

Discussion...
A broad trade-wind trough will very slowly cross the Marianas over
the next day or so. After bringing some thunderstorms over Rota this
morning, the area of convection along the trough axis has built
further north and very gradually west, maintaining scattered showers
and isolated thunderstorms over eastern Tinian and Saipan waters
through this afternoon. This troughing pattern, loosely connected
with a weak circulation far to the northeast, will bring on-and-off
scattered showers through the next couple of days as these features
shift west. Most of the shower coverage is expected for the CNMI as
the trough and embedded circulation to the northeast shift a weak
vorticity feature toward the islands, which looks to pass over the
northern CNMI through the end of the week. This will increase showers
across all the Marianas, especially around Thursday, but otherwise
Guam in particular will continue to see more of a relatively quiet
wet-season pattern.

Marine/Surf...
Mostly gentle east to southeast winds are expected to persist the
next few days. Combined seas of 3 to 4 feet will continue into the
weekend, comprised of a primary easterly trade swell and wind waves.
There is still a light west-northwest swell which will diminish
through the next day or so. For surf, a moderate risk of rip currents
continues for east facing reefs, but looks to diminish to low by
Wednesday morning as the easterly trade swell eases slightly.
Additionally, the light west-northwest swell looks to diminish
through the next day or so.

Tropical Systems...
A weak circulation, Invest 96W, continues to move away well west of
the Marianas with its center near 14.8N 129.7E, now just outside of
the region. Model guidance shows little development with 96W as it
continues westward towards the Philippines. To the northeast, the
circulation comprised of Invest 97W and what was once Tropical
Depression 14W, has shifted just outside of the region as well with
its center near 26.2N 159.8E. Models show little to no development
as this circulation looks to dissipate well north of the region over
the next few days.

Eastern Micronesia...
The two items of interest are a subtle trough approaching Kosrae, and
another trough in the trades that stretches from Makin in the
southern FSM to just west of the Date Line near 10N. The first trough
will bring an uptick in shower coverage tonight, so we have 30
percent probabilities for scattered showers at Kosrae. Then, the next
trough may start affecting Majuro in the next 24 to 36 hours.
However, the best convergence looks to be closer to 9N or 10N so it
remains to be seen if we`ll need to increase rainfall
coverage/probabilities here, as convection along the trough axis
south of 8N is pretty lackluster currently. Depending on how
convection evolves further south along the trough the next 24 hours
will dictate whether increases are needed here and later on at
Kosrae. Then as we head for the latter half of the week, the Majuro
trough slides overhead at Pohnpei, increasing rainfall potential
there.

As for marine conditions, look for light to gentle winds to prevail,
locally higher though near any strong shower or thunderstorm
downdrafts. Shall this occur, areal and temporal coverage looks
isolated at best (it`ll be brief). As such, we opted not to include
it in the forecast despite a respectable trough convergence
signature. Seas will be generally in the 3 to 5 foot range.

Western Micronesia...
Invest 96W continues to move farther northwest away from the region,
more than 500 miles from Palau and Yap. Afternoon satellite imagery
shows patchy showers over the main forecast locations with more
widespread showers and a few thunderstorms concentrated around a
broad trade-wind trough moving through eastern Yap State. This
trough is expected to increase showers around the main islands of
Palau and Yap Proper around midnight. Model guidance shows
disorganized convection surrounding this feature as it propagates
into the Philippine Sea, which will generally keep scattered showers
near Palau and Yap through Wednesday night. Then a weak ridge will
try to build in behind the trough on Thursday and Friday, decreasing
showers once again to isolated to low-end scattered. For Chuuk,
relatively quiet conditions persist over the next several days with
isolated to scattered showers expected within a weak, convergent
trade-wind pattern.

Over the weekend, ensemble models hint at a weak trade disturbance
or broad trough starting to develop that may bring another period of
scattered showers for Palau and Yap, and to a lesser extent Chuuk.

Overall, benign marine conditions continue. Buoy and altimetry data
show calm seas of 1 to 3 feet near Palau and Yap and up to around 4
feet near Chuuk. Winds remain light to gentle near Yap and Palau,
becoming light and variable at times. Meanwhile, scatterometry shows
light to moderate east-southeast trades farther east near Chuuk,
although winds are expected to subside back down to light to gentle
in the latter half of the weekend.

&&

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

&&

$$

Marianas update: Bowsher
East/West Micronesia update: Stanko
Marianas/Tropical: DeCou
East Micronesia: Doll
West Micronesia: Cruz