641
FXPQ50 PGUM 041742
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
342 AM ChST Thu Dec 5 2024

.Marianas Update...
Minimal changes were made to the forecast overnight. Conditions will
remain quiet across the Marianas for today and much of tonight, as a
dry air mass works its way west across the region. CIMSS Mimic Layer
Precipitable Water values fall below 1.3 inches just east of the
islands, and latest satellite and radar show mostly clear skies with
only a light stray shower or two in the area. Winds are gentle to
occasionally moderate. Local buoys show combined seas of around 5 to
7 feet, but altimetry shows higher seas of around 6 to 8 feet east of
the Marianas.

Showers will see an increase Friday into Saturday morning as a
surface trough moves west across the area with an accompanying plume
of deep moisture. Drier conditions resume by Sunday as a trade-wind
surge builds west into the region, which will lead to increasing seas
and surf. As a result, a high risk of rip currents may return for
east facing shores come Sunday due to an elevated incoming trade
swell.

&&

.Eastern Micronesia Update...
Minor changes were made to some of the wind and wave forecasts based
on current and expected near-term conditions. The ITCZ still looks
to re-assert itself late this week into early next week, with
multiple trade troughs/surges passes along it as well, bringing
another round of increased shower and thunderstorm potential with
gusty winds and heavy downpours possible.

&&

.Western Micronesia Update...
Minor adjustments were made to the Chuuk forecast to match current
conditions. Palau and Yap weather still remains fair this morning,
and for today, but patchy showers are still expected to gradually
arrive from the east in the coming days.

&&

.Prev discussion... /issued 524 PM ChST Wed Dec 4 2024/

Marianas Synopsis...
Visible satellite imagery and Doppler radar data shows scattered
showers departing the area. Seas continue to hold near 7 feet based
on the latest altimetry data, and the water temperature is 85
degrees.

Discussion...
The forecast remains on track. Precipitable water values have dropped
slightly from overnight values, currently near 2.5 inches. Just to
out east-southeast, much drier air, featuring a "tongue" with lower
values bottoming out near 1.2 inches have crossed 150E (~250 miles
east of us). This looks to get modified some as it arrives Thursday,
but it`ll be a much drier airmass none-the-less. Quick on its heels
though will be another moisture surge lifting northward, as a
surface trough crosses the region Friday. This will be short-lived
though, with dry air returning for the weekend into the first half of
next week.

Marine
Seas are currently near 7 feet, increasing to 8 feet once you get
about 100 miles offshore to the east. This will decrease by a foot
tonight and persist into Saturday, before seas increase 1 to perhaps
3 feet during the first half of next week. As for the winds, gentle
to moderate winds will prevail through Monday, but we cant rule out a
few fresh gusts on Sunday.

Eastern Micronesia...
The Inter-Tropical Convergence Zone (ITCZ) has fragmented and
weakened as the surface trough that brought heavy weather to Majuro
yesterday and Kosrae and Pohnpei yesterday and last night continues
to lift northwest away from the region. Only isolated trade showers
are occurring for Majuro today. A disturbance withing the
southeasterly flow in the wake of the trough is expected to keep
potential for scattered showers and isolated thunderstorms for
Kosrae through tonight and Pohnpei through tomorrow. Latest
scatterometry data is showing some gusty winds with these showers as
they lift northwest towards Kosrae and Pohnpei. Otherwise, isolated
trade showers expected for Kosrae through tomorrow and Pohnpei
through Friday. The reprieve looks to be short-lived as the ITCZ
looks to re-assert itself late week into early next week, with
multiple trade troughs/surges passes along it as well, bringing
another round of increased shower and thunderstorm potential with
gusty winds and heavy downpours possible.

Combined seas of 6 to 8 feet and moderate to fresh winds with
occasional strong gusts as the elevated trade flow persists. Seas
and winds look to rise beginning Thursday night and continuing into
the weekend as surges in trade winds and swell look to pass through
the region, with the potential increasing for marine conditions to
become hazardous to small craft. Current forecast has winds becoming
fresh to strong with near gale gusts, with seas rising to 8 to 11
feet. Surf could also become high along east facing reefs of Kosrae
by around Saturday.

Western Micronesia...
The weather at Palau and Yap has remained fair with light to moderate
trade winds and isolated showers, while most of the moisture located
near the equator, up by the Marianas or further east by Chuuk. At
Chuuk, a broad trough is pushing through and producing scattered
showers and isolated thunderstorms.

As the trough near Chuuk pushes westward, the potential for scattered
showers and isolated thunderstorms will increase at Palau and Yap
around Thursday night and linger into the weekend, while the
potential will slowly decrease at Chuuk from 50 percent tonight to
the 30 to 40 percent range through Saturday. Late this week and into
early next week, models show the ITCZ redeveloping across eastern
Micronesia, along with a surge in the trade winds. The ITCZ will
bring more showers and thunderstorms to Chuuk this weekend, while the
trade-wind surge may make conditions breezy at Chuuk the weekend,
with choppy seas making travel difficult for small boats. Yap and
Palau are currently far enough west the ITCZ and trade-wind surge are
not expected to have much of an impact for now, but a trough ahead
of the ITCZ is expected to move through this weekend, continuing the
overall wet pattern expected to move into Palau and Yap Thursday
night.

Satellite altimetry and buoy data near Palau show seas are around 4
feet at Palau and Yap. Over by Chuuk, seas are closer to the 5 to 7
foot range, due to a slightly stronger trade swell. This trade swell
is expected to slowly weaken through Friday, allowing seas around
Chuuk to decrease by about 1 to 2 feet. However, with a trade-wind
surge expected to develop across eastern Micronesia this weekend,
seas around Chuuk will rebuild, along with the potential for fresh
winds and strong gusts to create choppy seas. There is the potential
for conditions to become hazardous to small craft with seas of 10
feet at times and/or sustained winds exceeding 22 kts or frequently
gusting over that threshold, so monitor the forecast if planning to
travel by boat across or east of Chuuk State this weekend. For Palau
and Yap, seas may increase slight due to an increase in the trade
swell from the trade-wind surge, but not expecting an overall change
in sea conditions.

&&

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

$$

Marianas: DeCou
Micronesia: Simpson