Area Forecast Discussion
Issued by NWS Tiyan, Guam

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

FXPQ50 PGUM 250802

Area Forecast Discussion
National Weather Service Tiyan GU
602 PM ChST Sat Jun 25 2022

.Marianas Synopsis...
Partly sunny skies, moderate trade winds, and isolated showers are
found this afternoon across the Marianas. At the buoys, seas are
generally between 4 and 6 feet. On visible satellite, a trade-wind
disturbance is producing scattered showers and a few thunderstorms
southeast of the islands from 147E eastward to about 152E, heading
toward Guam and Rota.


While the GFS keeps showers out of Guam and Rota til Sunday morning,
it appears from satellite trends that the showers will likely get
in by around midnight, and have adjusted the forecast accordingly.
Otherwise, the rest of the forecast is basically the same as before,
with scattered showers for all the islands Monday night, then again
for Wednesday through the rest of the week. But it should be noted
that support from the GFS for scattered showers later in the week
has been waning in the last couple of runs. However, the ECMWF still
supports those showers, and have left the forecast unchanged for now
until the situation clarifies.


Seas are still expected to peak on Sunday, with heights up to 7 feet
east of the islands Sunday and Sunday night, then down to between
4 and 5 feet Monday night and Tuesday. Rip risk will remain moderate.


.Eastern Micronesia...
Only minor changes to the forecast. The progression of features
remains fairly straightforward. A series of trade-wind troughs
continues to move through the weak ITCZ pattern. One broad trough
is generating widespread showers across Kosrae and south of
Majuro. Some of the outflow boundaries near this feature were
somewhat faster than anticipated, so we now expect gusts to reach
up to 30 kts around the heaviest showers. Late tonight, showers
will have moved over Pohnpei. Went ahead and bumped up showers to
numerous, as guidance still indicates widespread moderate to
strong convection, becoming scattered by Sunday afternoon. Drier
air fills in behind this feature, where a day or two of quiet
weather may be expected starting late tonight for Majuro, Sunday
night for Kosrae, and Monday night for Pohnpei. Around midweek,
ITCZ starts to rebuild from the east restoring scattered showers
to the forecast through the latter half of the week.

Moderate trade winds are expected through the middle of next week,
however, mariners should be wary of gusty showers associated with the
trough explained in the above paragraph. Combined seas are between 4
and 6 feet, although Kosrae may see seas ranging up to 7 ft. Long-
period southerly swell starts to subside by the start of next week,
then another southern hemispheric storm may contribute another
southerly swell sometime late next week.


.Western Micronesia...
Southerlies converge with trade winds southwest of Palau, then lead
into a circulation southeast of Mindanao. This, as well as various
trade wind troughs keeps the region in an active weather pattern
this afternoon. Palau and Yap will continue to see widespread
cloudiness with scattered to numerous showers and isolated
thunderstorms tonight. Adjusted POPs for Yap tonight to reflect
satellite and model trends. They are expected to be in the wake of
their current trough later this evening. Similar to the previous
discussion, Palau remains precariously positioned between ridging
effects and southerly, monsoon-like flow around Tue-Wed time frame.
Currently, forecast depicts a scattered shower scenario, but we
can adjust in later forecast cycles. For Chuuk, the trough moving
through eastern Micronesia is expected to move over the island by
Sunday night, bringing an uptick in showers and gusts. Then, on
and off showers is all that can be prescribed until ITCZ coverage
perks up next weekend.

Continue to expect combined seas between 3 and 4 feet near Yap/Palau
and up to 5 feet near Chuuk. Gentle to moderate winds with gusts up
to 25 kts near heavier showers can be expected over the next several


Marianas Waters...None.



Marianas: Middlebrooke
Micronesia: Cruz is the U.S. government's official web portal to all federal, state and local government web resources and services.