512
FXPQ50 PGUM 231957
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
557 AM ChST Mon Aug 24 2026

.Marianas Update...
An unsettled, but disorganized monsoon pattern continues to bring
scattered showers and isolated thunderstorms across the Marianas this
week, with showers becoming numerous and locally heavy at times.
Model guidance shows a slight southward nudge in the monsoon trough,
where the nearby col shifts closer to Tinian and Saipan later today.
Showers and convectively-driven gusts become more focused across
Guam and Rota today and tonight, with the peak in numerous locally
heavy showers roughly timed between this afternoon and midnight. A
Small Craft Advisory remains in effect through this afternoon. A High
Surf Advisory and High Risk of Rip Currents along west-facing reefs
continue through this afternoon as well, potentially extending
through tonight.

&&

.Tropical Systems Update...
Typhoon Saudel continues to move west-northwest at about 18 mph,
away from the Marianas and is passing southwest of Iwo To. Saudel
is located near 23N138E, about 190 miles southwest of Iwo To, and is
expected to maintain this general course with a slight decrease in
forward speed through Tuesday. With this general track, Saudel is
forecast to move north of 25N and exit our region on Tuesday.
Maximum sustained winds remain at 125 mph. Saudel is forecast to
maintain this intensity through Tuesday, remaining a typhoon. For
more information on Typhoon Saudel (17W), please refer to the
Tropical Cyclone Warning from JTWC under WMO header WTPN31 PGTW, and
the TC Public Advisory from the National Weather Service under WMO
header WTPQ31 PGUM.

Tropical Depression 19W is located near 14N136E, about 331 miles
north-northwest of Yap and about 482 miles north-northeast of Koror.
19W is moving east-northeast at around 8 mph and is expected to make
a turn toward the north-northeast with a slight increase in forward
speed through Tuesday. 19W continues to move away from Yap and Palau
and remains well west of the Marianas. Maximum sustained winds remain
at 35 mph. 19W is forecast to maintain this intensity through
Tuesday. For more information on Tropical Depression 19W, please
refer to the Tropical Cyclone Warning from JTWC under WMO header
WTPN33 PGTW, and the TC Public Advisory from the National Weather
Service under WMO header WTPQ33 PGUM.

&&

.Eastern Micronesia Update...
A Small Craft Advisory was issued for Majuro through this afternoon.
Overnight scatterometry showed moderate to strong (15 to 25 kt) south
to southwesterly winds across Majuro and to the south. These
stronger winds and gusts are tied to an area of enhanced convergence
that is expected to shift northwest over the course of today, with
winds subsiding below hazardous levels of 22 kt in the afternoon.
Otherwise, the only change in the forecast was to delay numerous
locally heavy showers at Kosrae to the afternoon and included
occasional, convectively-driven gusts to 25 kt to today`s forecast
for Pohnpei and Kosrae.

&&

.Western Micronesia Update...
The Small Craft Advisory for Yap coastal waters was allowed to
expire earlier this morning. Overnight altimetry and recent buoy data
indicate that seas have fallen below hazardous levels of 10 feet. As
Tropical Depression 19W continues to move farther away to the north,
15 to 20 kt southwest winds trend down to 10 to 15 kt Tuesday.
Mariners should still exercise caution as combined seas of 7 to 9
feet persist through tonight, mainly across northern waters. Deep
convection tied to the monsoon tail following Tropical Depression 19W
remains near but will keep northwest of Yap and Palau, especially as
19W continues moving away and possibly weakening. No major changes
were needed for the forecast, infrared satellite imagery shows
scattered showers and isolated thunderstorms across much of the
region this morning, with convection deepening towards eastern Chuuk
State, associated with strengthening west to northwesterly
convergence across eastern Micronesia.

&&

.Prev discussion... /issued 1117 PM ChST Sun Aug 23 2026/

Marianas Synopsis...
Satellite imagery shows high-end scattered showers and isolated
thunderstorms across the Marianas coastal waters. Model guidance
suggests combined seas of 7 to 9 ft.

Discussion...
The Marianas is located within an unstable weather pattern due to
Typhoon Saudel`s (17W) monsoonal tail, cross-equatorial flow, and a
col to the east-northeast. Scattered showers today have steadily
increased to numerous across coastal waters, which will eventually
make its way over the islands before midnight. Gentle to moderate
southwesterlies with strong, convective gusts are expected at least
through Monday afternoon. Isolated thunderstorms are occurring and
will persist possibly through the rest of the week. There is
uncertainty regarding timing and intensity of heavy showers on
Monday, so the forecast reflects a 60 percent chance of showers. The
previously anticipated wet period starting on Tuesday looks to be
delayed a day or two, with flooding and mudslide potential most
likely in the latter half of the week. The forecast reflects the
slight lull in shower activity midweek before picking back up by the
weekend.

Marine...
Combined seas of 7 to 9 ft tonight will increase to 8 to 10 ft
tomorrow, so the previously issued Small Craft Advisory remains in
effect through Monday afternoon. In addition, strong, convective
gusts associated with heavy showers will give way to choppy seas. A
long-period southwesterly swell from Tropical Depression 19W (located
well to the west) will induce hazardous surf after tonight, and
allow the high risk of rip currents to remain along west-facing
reefs. There is a moderate risk of lightning throughout the week.

Hydrology...
A reinvigorated monsoon trough with a potential embedded tropical
disturbance will likely develop in the area and bring periods of
heavy rainfall to the Marianas starting midweek. Between Wednesday
and Friday, early ensemble guidance suggests 4 to 6 inches with a low
probability of up to 10 inches for Guam and Rota, and 3 to 5 inches
with a low probability of up to 8 inches for Saipan and Tinian. Heavy
showers will moisten soils throughout the event and increase
potential for mudslides. Residents of the Marianas need to closely
monitor this developing situation as flood watches, advisories and
flash flood warnings could be issued later in the week.

Tropical Systems...
Typhoon Saudel (17W) is centered near 22N140E, moving northwest at
18 mph. Maximum sustained winds are 125 mph near the center, with
this intensity persisting through Monday. Saudel is expected to make
a slight turn toward the west-northwest with little change in forward
speed through Monday as it heads toward Okinawa.

Tropical Depression 19W is centered near 14N136E, moving east-
northeast at 9 mph. Maximum sustained winds remain at 35 mph near the
center, with this intensity persisting through Monday, remaining a
Tropical Depression. TD 19W is to expected to continue to move into a
a favorable environment while pivoting toward departing TY Saudel
well to the north-northeast, with some resemblance of a distant
Fujiwara Effect. This is expected to help further prime the
environment around the Marianas for another enhancement in the
monsoon or potentially a weaker tropical disturbance to develop in
the area, bringing in another period of heavy rainfall to the region
later this week (more details in the Hydrology Section).

For more information on Typhoon Saudel (17W), please refer to the
Tropical Cyclone Warning from JTWC under WMO header WTPN31 PGTW, and
the TC Public Advisory from the National Weather Service under WMO
header WTPQ31 PGUM. For more information on Tropical Depression 19W,
please refer to the Tropical Cyclone Warning from JTWC under WMO
header WTPN33 PGTW, and the TC Public Advisory from the National
Weather Service under WMO header WTPQ33 PGUM.

Eastern Micronesia...
Pohnpei and Kosrae - short term:
The main forecast challenge was determining rainfall
coverage/potential through the first 36 hours. Currently, fairly
persistent shower activity has been ongoing for the past few hours.
However, recent infrared satellite imager shows rapid warming of
cloud top temperatures, while visible imager in addition to infrared
overcast skies. This is often a "stratification effect" after a
prolonged period of heavier showers and thunderstorm occurrence.
Thus, it`s highly likely that some high cloud-based light rainfall
continues from the a modest directional and speed shear environment
(based on the Pohnpei sounding and pattern recognition in the
numerical forecast guidance). Typically, this "stable bubble"
persists for 6 to 10 hours. With this in mind, we do expect increased
shower activity to redevelop, and this was reflected in tonight`s
forecast. The thought of adding "after midnight wording" was strongly
considered, for conveying when the best rainfall potential would
occur. However, good speed convergence in the low-level streamline
analysis, along with recent development south of Kosrae, precluded
this decision.

Majuro - short term:
Majuro too involved a little bit of a tricky forecast tonight and
tomorrow. as the best convergence and attendant convective
development is south and east of you per satellite imagery. However,
short term forecast guidance strongly suggests this backbuilding
line of convection will slide north with time, potentially even
before midnight. This is supported in the latest satellite imagery as
well. Thus we precluded any more specific temporal refinement to the
forecast.

Extended outlook for all three locations (36 hours to day 7):
Forecast guidance and pattern recognition all points to at least
scattered shower potential continuing into next weekend, with a few
thunderstorms mixed in from time to time. A tropical
disturbance/circulation located east of Pohnpei/northeast of Kosrae
will not only maintain respectable convergence in the cyclonically-
enhanced monsoon flow, but there may be a few periods of locally
increased shower coverage and intensity.

Marine and surf conditions:
A west to southwest primary and secondary swell will continue through
the weekend at Pohnpei and Kosrae, with a slight backing of swell
direction due to the previously-mentioned cyclonic flow in the
monsoon environment, will allow for a southwest and south swell
direction to continue at Majuro. This swell regime will continue to
be augmented by the persistent cross-equatorial flow/swell pattern.
The net result is elevated surf concerns will continue the next
several days at Kosrae and Majuro as well. Otherwise, mainly gentle
to light winds currently, may become light to gentle from time to
time, especially for the latter half of next week. Seas of 5 to 7
feet are anticipated through the forecast period.

Western Micronesia...
As Typhoon Saudel well northwest of the Marianas and Tropical
Depression 19W north-northwest of Yap continue to move away from the
region, the last pulse of a fresh to strong southwesterly monsoon is
expected to bring more patchy showers Yap tonight. While winds are
expected to diminish slightly thereafter, a reigniting monsoon surge
is still expected to pummel Yap and much of eastern Yap State the
next several days, with a peak shower and thunder coverage expected
Tuesday and Tuesday night. A tropical ridge anchored just north of
the Equator is expected to bring a dry spell to Palau beginning
Monday night, which is likely to last for the rest of the week. While
moist westerlies are expected to continue at Chuuk for most of the
forecast period, the aforementioned tropical ridge will allow Chuuk
to fall in between the convectively active pattern hugging 10N and
the much quieter sector of the Equator between Indonesia and
Kapingamarangi. This will allow patchy showers and some thunderstorms
to form at Chuuk for much of the forecast period, followed by a
drying trend in the second half of next week as a larger buffer
circulation induces more diffusive flow.

The aforementioned monsoon pulse and remaining significant
southwesterly swells and fresh to strong winds continues to produce
sea conditions hazardous to small craft, which are expected to fall
below hazardous criteria by sunrise on Monday. In the meantime,
combined seas of 5 to 7 feet in Palau waters are expected to taper
down a few feet over the next few days as the southwesterly swell
diminishes, being slowly replenished by various smaller northerly
swells building in. Combined seas of 5 to 7 feet are expected to
slowly drop a foot or two toward the next weekend as swells and
localized wind waves diminish.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...High Rip Current Risk through this afternoon for GUZ001.

     High Surf Advisory until 4 PM ChST this afternoon for GUZ001.

MP...High Rip Current Risk through this afternoon for MPZ001>003.

     High Surf Advisory until 4 PM ChST this afternoon for MPZ001>003.

Marianas Waters...Small Craft Advisory until 5 PM ChST this afternoon for PMZ151>154.

&&

$$


Marianas/East and West Micronesia/Tropical Update: Cruz
Marianas/Hydrology: Mesa
East Micronesia: Doll
West Micronesia/Tropical: Montvila