528
FXPQ50 PGUM 221750
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
350 AM ChST Thu Jan 23 2025

.Marianas Update...
The Marianas remains in a dry trade-wind pattern as both the 12Z
RAOB and CIMSS MIMIC TPW satellite product shows precipitable water
(PWAT) around 1.29 to 1.42 inches across the Marianas. This morning`s
forecast continues the established continuity of last couple of
forecasts, forecasting a seasonably dry pattern for the next couple
of weeks.

Buoys around the Marianas are still reporting seas between 5 and 8
feet, driven primarily by the trade-wind swell and wind waves, with
a weak but long-period north still present. Stronger north to
northeast winds north of a decaying front into a shear line in the
far northern Mariana Islands and systems pushing off of Japan, will
generate pulses of north swell that may reach up to around 5 or 6
feet at times, keeping surf elevated and the risk of rip currents
moderate along north facing reefs. Meanwhile, the east swell is
expected to diminish a couple of feet this weekend, allowing
combined seas to drop to around 4 to 6 feet by early next week, but
surf along east facing reefs should stay high enough to keep a the
risk of rip currents moderate.

&&

.Eastern Micronesia Update...
Not much change was made to the forecast as altimetry and
scatterometer data shows the forecast is in good shape. The models
were a little fast in increasing convection at Majuro today, with
morning satellite imagery showing a dearth of convection. However,
better surface convergence is just east of you, and although this
looks to pass to your south, with Precipitable Water Values (PWATs)
generally in the 2.25 to 2.5 inch range, and alignment of convection
developing to your east (which stands a fair shot of at least making
it into your southern coastal waters), we opted to push back timing
of increased coverage until this afternoon.

&&

.Western Micronesia Update...
No significant changes were made to the forecast. A surface trough to
the east looks to increase rainfall potential at Palau in the next
24 to 36 hours, with determining scattered versus numerous coverage
the task at hand for the day shift to determine.

&&

.Prev discussion... /issued 519 PM ChST Wed Jan 22 2025/

Marianas Synopsis...
Dry conditions are seen across the region with shallow moisture
limited to only the lower 6000 ft, as noted in today`s 00Z RAOB. A
few trade-wind showers are seen passing by to the south with fair-
weather cumulus off to the east of the Marianas. Buoys and altimetry
data show seas of 5 to 6 ft west of the Marianas and 6 to 8 ft to
the east.

Discussion...
The latest forecast maintains continuity from the previous forecast,
ultimately calling for a seasonably dry couple of weeks. Very little
rainfall is expected beyond loosely-clustered passing trade-wind
showers. Surface winds will subside over the weekend as a front
passes well to the north. Under a wetter regime, such a light wind
pattern could be supportive for island-effect showers, but with
modeled soundings indicating PWATs below 1.3in, only a small line of
clouds extending downwind from the islands would be the expectation.

Marine...
A mix of longer-period north swell and trade-wind waves and swell
will maintain seas of 6 to 8 ft the next several days. While north
swell will periodically pulse up to around 5 or 6 feet, easterly
swell will begin to subside over the weekend with combined seas
ultimately expected to settle around 4 to 6 feet by early next week.
Surf will be high enough along north and east facing reefs to
maintain a moderate risk of rip currents the next several days.

Eastern Micronesia...
Extended High Surf and Small Craft Advisories for Majuro and High
Surf Advisory for Kosrae. Small Craft Advisories for Pohnpei and
Kosrae no longer in effect, and High Surf Advisory for Pohnpei no
longer in effect. Except for some higher waves and winds near the
Marshall Islands, buoy reports indicate that marine conditions have
trimmed down slightly across the region. BUT, its tricky because
models indicate fresh to strong winds and some higher seas could
return to Eastern Micronesia by the weekend.

Weatherwise, satellite shows showery weather in a broad convergence
zone that extends from the Date Line between about 4N and 8N, across
the Marshall Islands to Kosrae, and to near Pohnpei. Models indicate
this pattern will remain active and spread showers farther westward
during the next few days, at least. Majuro, especially for tonight
and Kosrae for the longer term, will be most at risk for occasional
heavy showers. Models indicate a gradual drying trend can be expected
next week.

Western Micronesia...
A couple of trade-wind troughs are moving across the region
generating mostly cloudy skies and scattered showers. One is
propagating westward through eastern Yap State and the other is
passing near and south of Chuuk Lagoon this afternoon. Left in
scattered showers for Chuuk this evening, but may see showers
downgrade to isolated overnight as this trough pushes westward and
weakens. Breaks in a convergence zone to the south will keep showers
isolated to scattered over Chuuk for another day or two, then a
developing convergence zone shifts northwestward into the region in
the latter half of the week, showing more of an unsettled weather
pattern starting Friday. Models show the convergence zone possibly
shifting back south by the middle of next week. In far western
Micronesia, an approaching trade-wind trough is expected to reach
Palau and Yap after midnight, bringing scattered showers over Yap
Thursday morning and through the afternoon for Palau. Model guidance
still shows an increase in trade convergence in the wake of a weak
disturbance in a Near-Equatorial Trough (NET), well to the southwest,
near North Maluku. Being on the northern peripheries, Yap can expect
mainly isolated showers whereas scattered showers across Palau are
expected late this week and over the weekend.

Palau buoy shows seas between 5 to 6 feet and altimetry data
indicate seas between 5 to 8 feet farther east near Chuuk. North
swell is expected to diminish over the next few days then another
pulse of north swell, around 2 to 4 feet, is expected to arrive late
week and over the weekend to Palau and Yap. This would only amount to
4 to 6 foot surf, so no advisories are expected through early next
week. Trade swell is expected to increase another foot or two this
week, with the highest seas near Chuuk, reaching up to 10 feet by
Friday, when a Small Craft Advisory would be needed. Wind are
moderate to fresh, becoming strong at times near Chuuk late this
week.

&&

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

$$

Marianas: Schank
East/West Micronesia: Doll