338
FXPQ50 PGUM 220808
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
608 PM ChST Sat Nov 22 2025

.Marianas Synopsis...
Satellite and radar early this evening show isolated showers and
partly cloudy skies across the Marianas, with similar conditions
persisting upstream. Swaths of upper-level clouds are streaming in
from prior deep convection to the southeast, mainly over Guam coastal
waters. Buoy and altimetry data indicate combined seas of 7 to 9
feet.

&&

.Discussion...
A dry trade-wind pattern is expected to continue through much of next
week, with just isolated showers in the forecast until next weekend.
CIMSS MIMIC Total Precipitable Water (TPW) imagery shows a plume of
drier air moving in from the east, with TPW values of 1.6 to 2.2
inches falling to 1.2 to 1.5 inches just east of coastal waters.
Winds will remain elevated over the next few days with an expected
peak on Sunday, before the regional pressure gradient begins to
diminish in the latter half of next week. Although still a ways out,
current model guidance depicts an increasingly wet pattern beginning
near the end of next week, as the first in a series of weak troughs
crosses the area.

&&

.Marine/Surf...
Moderate to fresh trade winds will prevail across the region through
at least the middle of next week. Altimetry and buoy data indicate
combined seas have tapered to 7 to 9 feet over coastal waters,
just below conditions hazardous to small craft, and the Small
Craft Advisory has been allowed to expire. However, seas will be
choppy, remaining around 7 to 9 feet for at least the next few days
as elevated trade swell and localized wind waves persist. A slight
increase in winds and gusts Sunday will contribute to additional
choppiness. The elevated easterly swell will maintain a high risk of
rip currents along east facing reefs through at least Monday night,
while a moderate risk of rip currents is expected along north and
south facing reefs through at least Sunday night.

&&

.Eastern Micronesia...
Winds have subsided enough for the Small Craft Advisory to be
cancelled at Pohnpei, as the trade wind surge north of the region
has weakened slightly. However, the associated northeasterly swell
from those higher winds remains sufficient to maintain the High Surf
Advisory for north facing reefs of Pohnpei and north and east facing
reefs of Kosrae. This looks to continue for a few more days.

Otherwise, eyes turn to a TUTT (Tropical Upper Tropospheric Trough)
cell that`s now shown in both the GFS and ECMWF fields, with this
upper low looking to develop near 10N170E over the weekend, with a
trough extending southwest towards Kosrae. Meanwhile, a surface
trough approaching Majuro will continue to head west. Moisture has
been pooling today along this feature with the latest MIMIC water
vapor imagery now showing a pocket of 2.5 inches or more of
precipitable water east of Majuro. If the models continue to show the
TUTT cell and MIMIC imagery to show deepening moisture, then shower
and thunderstorm potential may need to be increased at Pohnpei and
Kosrae for the first half of next week. Additional disturbances in
the trades should keep at least scattered showers and a few
thunderstorms in the forecast at Majuro for the forecast period.

&&

.Western Micronesia...
A Near-Equatorial Trough (NET) remains across the southern half of
the region, passing just south of Palau`s coastal waters to a broad
circulation near 4N140E, then continues southeast to EQ152E.
Unsettled weather continues across much of the region due to several
troughs traveling along the northern edge of the NET and a trade-wind
surge affecting parts of Yap and Chuuk states. As the NET disturbance
continues to develop, gusty showers, choppy seas, and locally heavy
showers and thunderstorms are to be expected for Yap and Palau
through the weekend. Visible satellite imagery this afternoon reveals
numerous showers and isolated thunderstorms over Palau, with only
scattered showers around Yap, however model trends continue to
indicate that showers will build in around Yap later tonight and
Sunday as the NET disturbance drifts west-northwest and convergence
to its north increases over Yap, bringing numerous to widespread
locally heavy showers and strong gusts through Sunday night. As the
NET disturbance moves west of Palau and Yap and towards the
Philippines Monday and Tuesday, showers and the potential for gusty
winds will steadily decrease, likely leading to isolated showers and
winds around 5 to 15 kt around the middle of the week.

For Chuuk, showers along a trough and the trade-wind surge moved
through earlier this afternoon and are gradually decreasing. CIMMS
MIMIC TPW shows an area of drier air behind this feature, allowing
for a lull in showers later tonight and Sunday. Then, isolated to
scattered showers are expected as minor troughs pass through for much
of the work week.

Altimetry data indicates elevated seas of 6 to 9 feet across the
region and ASCAT analysis shows gentle to moderate winds across Palau
with moderate to fresh winds across Yap and Chuuk. A Small Craft
Advisory has been issued for Yap through Sunday afternoon after
seeing support in latest model guidance for winds increasing to
around 22 kt and the 00Z sounding revealing a gradient wind of 35 kt.
The northeast swell generated by the trade-wind surge continues to
support elevated surf along north and east facing reefs of Chuuk,
but surf is expected to peak around 8 feet along north facing reefs
and 9 feet along east facing reefs, below the hazardous threshold of
9 feet for north facing reefs and 12 feet for east facing reefs. In
the latter half of the week, seas decrease to 5 to 7 feet as the
trade-wind surge and swell begin to subside.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...High Rip Current Risk through late Monday night for GUZ001.

MP...High Rip Current Risk through late Monday night for MPZ001>003.

Marianas Waters...Small Craft Advisory until 6 PM ChST this evening for PMZ151>154.

&&

$$

Marianas: DeCou
East Micronesia: Doll
West Micronesia: Cruz