164
FXPQ50 PGUM 111734
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
334 AM ChST Fri Jul 12 2024

.Marianas Update...
Latest satellite imagery is showing mostly cloudy skies and scattered
showers. A few lightning strikes have also been observed over the
coastal waters.

Multiple surface troughs and deeper moisture continue to pass
through the Marianas. Increased shower coverage through Saturday
based on satellite and model trends. Thunderstorms are possible as
instability increases and a TUTT cell moves into the region and looks
to provide some upper-level support. Drier conditions expected for
Sunday and Monday, but models are showing an increase in showers and
thunderstorms by around Tuesday as surface troughing and moisture
creep north out of Micronesia.

Marine and surf forecast had minimal changes in the overnight
package.

&&

.Eastern Micronesia Update...
Activity is beginning to develop across the region with the ITCZ
expected to be active through next week. Showers are expected to be
scattered today then numerous tonight for Kosrae. For Pohnpei,
scattered showers today and tonight. For Majuro today, active
weather is expected to pass south of their waters, then on Saturday
as a trough develops along the ITCZ, showers lift north to bring
scattered showers. Breezy conditions look to push into Majuro Monday
through Tuesday, so expect seas to increase as well due to both
developing both wind and swell waves.

Latest altimetry reported combined seas of 4 to 6 feet over the
waters east of Majuro and west of Kosrae. Expect a slight increase in
seas for Majuro on Monday.

&&

.Western Micronesia Update...
Trade wind convergence ahead of an encroaching monsoon trough is
developing showers across the region, mainly south for the moment.
Heavy shower activity surges just south-southeast of Palau, and
latest IR shows new cells building just to Palau`s east. Model
guidance suggests heavy shower activity will graze Palau and Chuuk
from time to time, but mainly staying just south. Conditions will
stay wet and turbulent across the region for much of next week. The
GFS remains rather aggressive and wants to develop a circulation or
two late next week. Worth keeping an eye on, but there isn`t much
agreement with other models this far out.

For Palau, a region of strong convergence is shifting into its near
vicinity just to the south, bringing heavy showers and embedded CBs
with it. New cells are beginning to form just north of this
convergence region just east of Palau, which may soak the area as the
disturbance moves past. Showers look to continue through the first
half of next week.

For Yap, showers remain just to the south, organized loosely along a
diminishing area of trade wind convergence. Yap looks to stay fairly
dry right along the northern periphery as showers pop in and out.

For Chuuk, scattered showers build in the vicinity as a broad
westward-moving trough pushes past Pohnpei. Some lightning has been
seen in approaching cells to the east. Scattered shower development
should continue into next week.

Combined seas are expected to be 3 to 5 feet. Winds near Palau and
Yap will be light to gentle, while in Chuuk winds are expected to be
light to moderate.

&&

.Prev discussion... /issued 623 PM ChST Thu Jul 11 2024/

Marianas Synopsis...
Satellite shows widespread cloudiness over the region as the
thunderstorm activity from earlier today has for the most part
stratified out. There are still areas of patchy light rain and
scattered showers nearby. Surface winds are gentle, and gradient
winds were from the east at 18 mph. Ritidian Buoy shows combined seas
mainly 4 to 5 feet, with occasional 6 to 8 feet waves through the
Rota Channel.

Discussion...
An upper level trough along with a weak trade-wind trough combined
to trigger a few heavy thunderstorms today over the region. The
pattern seems to be nearly stationary or at least slow moving. A few
showers and thunderstorms can be expected to develop overnight and on
Friday, then gradually taper off by Saturday night. The longer range
models for next week indicate a moist troughing pattern could
develop across the Mariana Islands.

Marine...
Gentle to moderate winds and combined seas of 3 to 5 feet are
expected the next few days. Winds and seas will be higher near
showers and thunderstorms. The moderate risk of rip currents will
continue along east facing reefs, and a low risk along other reefs,
with little change through this weekend. There will be a moderate
risk of lightning tonight through Saturday night.

Eastern Micronesia...
Satellite imagery shows mostly cloudy skies with diminishing showers.
These showers are in line with two troughs. The worst of the showers
are over Majuro, Kwajalein, Alinglaplap and Mili. the largest cells
are near Ailinglaplap and Kwajalein. Cloud tops were reaching to -80s
which indicates heavier rains. Lightning has been observed in these
cells.

Kosrae is beginning to clear out as most of the showers there have
stratified out. Cloud cover remains overcast.

Over Pohnpei is where the other trough is. The showers along this
trough`s axis are also diminishing. There is a large cell south of
Pohnpei and this cell is heading towards Pohnpei and Sapwuafik. This
cell has produced some lightning. Cloud tops are around -70s, Showers
may be heavy for a short period.

Combined seas of 4 to 6 feet are near Majuro. Seas are expected to
gradually rise over the week. Winds are expected to be gentle to
moderate for Pohnpei and Kosrae, and gentle to fresh for Majuro.

Western Micronesia...
A monsoon trough has pushed into the region. The combination of this
and the trade winds and a weak circulation are what is causing the
showers in the region. For the moment, the main island of Palau has
diminished in showers. A rather large cell is southeast of Yap to
near the equator. The GFS model is being overly aggressive as per the
usually. It is suggesting that something may spin up at the end of
its run. Little weight should be associated here, due to how
aggressive GFS normally is and how far out this system is. The ECMWF
does agree with that this region is very turbulent and things have
some potential.

For Palau, showers for the moment have diminished. This is not
expected to last as models suggest that wet season has arrived.
Shower are expected through the early part of next week.

For Yap, showers look to be just south of Yap proper. The northern
line of where the showers will be is expected to flex in and out of
Yap.

For Chuuk, showers have moved from the area. Cloud cover remains
scattered. Showers are expected to return when the trough near
Pohnpei moves westward.

Combined seas are expect to be 3 to 5 feet. Winds near Palau and Yap
are expected to be light to gentle, while in Chuuk winds are expected
to be light to moderate.

&&

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

&&

$$

Marianas: Slagle
East Micronesia: Hong
West Micronesia: Decou