497
FXPQ50 PGUM 191707
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
307 AM ChST Fri Sep 20 2024

.Marianas Update...
No major forecast changes this morning. Fair weather is anticipated
for the most of the weekend. Starting around Sunday night, showers
may increase as a passing trade-wind trough may traverse the region.
The east swell remains the dominate swell. The west swell is slowly
diminishing through the beginning of next week. Overall, seas are
expected to be fairly benign.

&&

.Eastern Micronesia Update...
Only minor updates made to the forecast this morning. The ITCZ
(Inter-Tropical Convergence Zone) and embedded troughs are building
west across the region, bringing numerous showers and isolated
thunderstorms to Majuro and scattered showers and isolated
thunderstorms for Kosrae and Pohnpei. The ITCZ and troughs will shift
north and dissipate by late weekend, a drier trade-wind pattern
expected for most of next week.

Benign marine conditions will continue with combined seas 2 to 4
feet and light to gentle trade winds, though Majuro could see
occasionally moderate winds through tonight.

&&

.Western Micronesia Update...
No major forecast changes this morning. Scattered showers and
isolated thunderstorms possible for Yap and Palau today as weak
surface trough passes through, along with some upper-level support
with a Tropical Upper-Tropospheric Trough (TUTT) drifts overhead. For
the weekend through mid next week, scattered showers and isolated
thunderstorms possible at times as another surface trough slowly
passes through the region.

Scattered showers and isolated thunderstorms possible for Chuuk
through Saturday as the ITCZ and surface trough passes through. As
the trough and ITCZ drift northwest, shower and thunderstorm
potential diminish as surface ridging build in.

Benign marine conditions expected with light to gentle winds and
combined seas 2 to 4 feet. Seas look to dip about a foot for next
week.

&&

.Prev discussion... /issued 531 PM ChST Thu Sep 19 2024/

Marianas Synopsis...
Satellite imagery shows some showers and thunderstorms within the
coastal waters, but most are away from the islands. Wind observations
at the airports are reporting a gentle to moderate east-southeast
winds, while buoys and altimetry show seas around 4 to 5 feet.

Discussion...
The Tropical Upper Tropospheric Trough (TUTT) and embedded upper-level
low is passing to the north of the Marianas this evening and helped
to spark isolated thunderstorms across the Marianas, especially just
north of Saipan and Tinian. So far most of these thunderstorms have
avoided passing directly over the islands, as here on Guam, we have
not measured any rain here at the airport and weather office and it
has been a similar story for Rota, Tinian and Saipan. Until the TUTT
passes far enough to the northwest, the potential for thunderstorms
and showers remains elevated tonight. Friday through Saturday night
looks to be fairly dry as there nothing to our east that catching our
attention to greatly increase the potential for showers or cause a
big change in our winds. The next trough or series of trough is
expected to move in Sunday night or Monday, but models are not
indicating anything major beside some scattered showers through
Tuesday, before drying out again.

Marine...
Mainly gentle to occasional moderate trades are expected through the
weekend. The southwest to west swell will continue to decrease
through the week allowing seas around 4 to 5 feet, to drop to 2 to 4
feet this. The decreasing of swell swill also allow surf to slowly
drop along west facing reefs and allow the risk of rip currents to
become low along all reefs. The TUTT will keep a moderate risk of
lightning through tonight. Shower and thunderstorm chances then drop
for Friday through Sunday.

Eastern Micronesia...
The main player in the forecast for eastern Micronesia continues to
be the ITCZ (Inter-Tropical Convergence Zone). The ITCZ stretches
eastward from near Kosrae to just south of Majuro to across the Date
Line. Convection has held off a bit through this afternoon and it
appears this will continue into the evening. Therefore, backed off on
the timing for increased showers to move into Majuro and Pohnpei. For
Kosrae, scattered showers associated with the ITCZ are now moving
into the area. With a trade-wind trough moving through the Marshalls,
scattered showers and isolated thunderstorms look to move across the
atoll later this evening. As the trough continues west, increased
showers look to continue across Kosrae Friday as the trough
interacts with the ITCZ over the state. The ITCZ should remain
active through Saturday. Majuro will see the most activity Friday and
Friday night as a couple of stronger troughs move in from east of
the Date Line, bringing numerous showers to the atoll. By Saturday,
the ITCZ looks to dissipate, though scattered showers remain possible
for Kosrae and Pohnpei as the subsequent troughs move through. By
Sunday, expect a dry trade-wind pattern to move into the area and
continue through at least the middle of next week.

Benign marine conditions will continue for the next several days,
with mostly light to gentle trade winds, though Kosrae and Majuro
could see occasionally moderate winds Friday into the weekend.
Combined seas look to remain between 2 and 4 feet.

Western Micronesia...
Satellite observations show isolated showers across Palau, Yap, and
Chuuk and much of Micronesia. Combined seas are generally between 2
and 4 feet with the Ngaraard, Babeldaob buoy just under 3 feet.

The surface ridge that was over Palau and Yap has slowly progressed
westward as a surface trough approaches the region. Scattered showers
will be possible along the trough over the next few days as it slowly
moves eastward. Seasonal showers are expected towards the latter half
of next week behind the trough. Seas will generally remain in the 2
to 4 ft range for Yap and Palau with gentle to moderate winds in
place.

Seasonal showers are expected for Chuuk through much of the period
except for some increased activity Friday and Saturday as the ITCZ
pulses up. The marine forecast for Chuuk is similar to Yap and Palau
with predominantly 2 to 4 feet seas. Seas may fall to 1 to 3 feet
late next week. Winds will remain gentle to moderate across Chuuk
State through the period.

&&

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

&&

$$

Marianas: Bowsher
Micronesia: Slagle