217
FXPQ50 PGUM 140759
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
559 PM ChST Tue Oct 14 2025

.Marianas Synopsis...
Moderate to fresh southeasterlies prevail across the region.
Satellite imagery and Doppler radar indicate slow-moving but steady
rows of showers moving into Rota waters. Buoys indicate seas are
around 5 to 7 feet.

&&

.Discussion...
A generally unsettled pattern caused by nearby tropical disturbance
Invest 96W embedded within an east-west oriented trough, is likely to
produce heavy showers and thunderstorms to bring localized flash
flooding risk to Guam and Rota for at least the next few days.
Heavier showers and thunderstorms are expected to begin after
midnight, to then peak in coverage and intensity Wednesday. As such,
a Flash Flood Watch has been issued for Guam and Rota through late
Wednesday night. Uncertainty remains high regarding wind potentials
due to the lackluster nature of the synoptic regime involving Invest
96W, but at this time, breezy winds of 25 mph with gusts to 35 mph
are possible Wednesday over Guam and Rota. Weather conditions are
expected to be slightly better at Tinian and Saipan, while also
dodging most of the more intense outflow boundaries produced by 96W.
Invest 96W is expected to exit the region before the weekend, to then
intensify in the open waters of the Philippine Sea as it heads
towards Luzon during the weekend. This will allow conditions to
improve considerably beginning Thursday, with a return to a drier
regime expected toward the weekend across the Marianas.

&&

.Marine...
Fresh to strong southeasterlies, as well as increasing southeast
wind waves, will produce conditions hazardous to small craft through
at least late Wednesday night. As such, a Small Craft Advisory has
been issued through late Wednesday night. Conditions are expected to
steadily improve once Invest 96W moves away from the region to the
west in the second half of the week. Combined seas of 6 to 8 feet
near Guam and Rota, and 5 to 7 feet near Tinian and Saipan tonight,
will taper down a few feet by Thursday, once wind waves decrease
after Invest 96W`s passage.

&&

.Hydrology...
The most recent model guidance and satellite interpretation analysis
indicates rainfall potential of 3 to 5 inches possible over Guam and
Rota over the next 48 hours. If rains persist, soils may become
saturated with any additional rain resulting in pure runoff, which
may exacerbate flash flooding potential further into the week. Based
on the most recent data, rainfall is expected to taper down
significantly after 96W`s exit, resulting in lesser shower potential
for the rest of the week.

&&

.Tropical systems...
A loosely organized tropical disturbance known as JTWC`s Invest 96W,
has a center axis of momenta just near 11N146E well southeast of
Guam. Moderate to occasionally deep convection is associated with
this feature, mainly associated with the east-west oriented trough
within which this disturbance is embedded in. Invest 96W is still
rated LOW by JTWC, meaning development into a tropical cyclone is
unlikely within 24 hours. While the system remains with no
discernible center of rotation, a sharpening leading edge of the
trough will be the vorticity center on which 96W will latch onto as
it crossed the Marianas, deepening the convection as it exits to the
west. This feature will then intensify in the open waters of the
Philippine Sea as it heads towards Luzon during the weekend. For
updated information on 96W, please refer to the Significant Tropical
Weather Advisory, issued by the Joint Typhoon Warning Center, under
WMO header ABPW10 PGTW.

A trade-wind disturbance is centered near 4N162E just southwest of
Kosrae. Moderate to deep convection is associated with this feature,
producing numerous to widespread showers and isolated to scattered
thunderstorms across a wide sector of eastern Micronesia from 160E to
170E, between 2N and 7N. This feature is expected to lose its center
of rotation and bulk of convection overnight, dissipating into
moreso a broad surface trade-wind trough that will continue to move
along the trades over the next several days.

&&

.Eastern Micronesia...
A tropical disturbance is producing an low located near 4N162E (just
southwest of Korea),and trough extending from the low to east of
Majuro near 7N175E. The showers associated with this disturbance are
numerous to widespread with isolated thunderstorms and covering most
of the central region of eastern Micronesia. The heaviest showers
are moving towards Kosrae. A call from WSO Pohnpei informed us that
0.77 inches had fallen by around 12:30 PM ChST.

This disturbance is expected to arrive at Pohnpei around Thursday.
Model guidance suggests, this disturbance will continue into western
Micronesia as a trough over the weekend. Along the eastern boarder,
the Intertropical Convergence Zone (ITCZ) is anticipated to build
back in over the weekend bring more showers back to the region.

Altimetry shows combined seas of 5 to 6 feet near Pohnpei and Kosrae,
and 6 to 7 feet near Majuro. Both North Point and Utwe buoys confirm
the heights near Pohnpei and Kosrae respectively. Winds are expected
to be light to gentle over much of the region, with a caveat of
moderate winds near heavier showers. There are two swells at play
here, the north swell of about 4 to 6 feet coming from distant
Tropical Nakri. The other swell is a southeast swell of about 3
feet. Surf along north facing reefs are expected to be elevated,
however are expected to be below the 9 foot threshold for an high
surf advisory.

&&

.Western Micronesia...
Scatterometer data shows a westward moving, elongated circulation
centered east of Palau and south of Yap, near 6N137E. This
circulation was part of of the area monitored as Invest 96W, but as
discussed in previous discussions, this circulation was expected to
remain elongated. More attention is now on the sharp trough heading
towards the Marianas, which is where Invest 96W was relocated this
morning, and is now centered near 11N146E. Scattered showers and
isolated thunderstorms are still developing along the elongated
center and are moving across Palau this evening and expected to move
through Yap Proper later tonight. The potential for scattered showers
and isolated thunderstorms will linger through Wednesday as the
elongated circulation drifts off to the west, potentially opening
back up into a trough. Depending on how Invest 96W develops as it
moves west of the Marianas, gentle south to southwest flow may
develop across Palau and Yap Wednesday through Thursday, before
turning southeast to east late this week as a trough approaches the
region, potentially prolonging scattered showers and periods of
isolated thunderstorms across Palau and Yap into the weekend.

For Chuuk, with Invest 96W moving closer to the Marianas, dry weather
has moved across Chuuk Lagoon and is spreading westward. This drier
weather will continue through tonight, but a broad trough with an
embedded circulation near Kosrae will continue to drift westward.
This will lead to showers starting to increase as early as Wednesday
afternoon. However, models show the embedded circulation dissipating,
with the vorticity moving north of Chuuk, this may keep showers on
the low-end of coverage across Chuuk, with showers favored more
along 10N later this week. Winds are expected to be easterly and
mainly light to gentle, occasionally becoming moderate with the
passage of troughs.

Satellite altimetry shows seas around 4 to 5 feet across the region,
mainly driven by the north to northeast swell. Surf along north
facing reefs will remain elevated across Palau, Yap, and Chuuk this
week, due to pulses of longer-period northerly swell moving through
the region, but are expected to remain below hazardous levels of 9
feet.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...Flash Flood Watch through late Wednesday night for GUZ001.

MP...Flash Flood Watch through late Wednesday night for MPZ001.

Marianas Waters...Small Craft Advisory until 6 AM ChST Thursday for
     PMZ151-152.

&&

$$

Marianas/Tropical: Montvila
East Micronesia: Bowsher
West Micronesia: Schank