940
FXPQ50 PGUM 262029
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
629 AM ChST Wed Nov 27 2024

.Marianas Update...
Little change was made to the weather forecast. Introduced low-end
scattered showers in the forecast for tonight at Guam and Rota, as a
minor perturbation upstream is expected to arrive slightly earlier
before Thanksgiving Day. Based on Satellite intepretation, radar
velocities, and recent scatterometry passes, higher-end winds with
gale-force gusts are less likely to occur, but conditions will
continue to remain hazardous to small craft.

&&

.Eastern Micronesia Update...
Minor updates to eastern Micronesia this morning. At Pohnpei, reduced
swell slightly based on the latest ECMWFwave guidance, and increased
showers tonight to numerous from scattered. Similar at Kosrae, except
the showers tonight are widespread, one of the categorical
qualifiers. At Majuro, extended the numerous showers from last night
into tonight, then merged that into the previous forecast. These were
based on a combination of model and satellite trends.

For Pohnpei Waters, winds will be challenging at 10 to 20 knots. Seas
will start at 5 to 7 feet, then finish for the weekend at 7 to 9 feet
which is itself challenging, just short of Small Craft advisory
criteria.

For Kosrae Waters, winds will also be challenging at 10 to 20 knots,
although possibly a knot or two less than at Pohnpei. Seas will start
out at 4 to 6 feet then end over the weekend at a similar 7 to 9
feet.

For Majuro Waters, a familiar refrain, winds will be challenging at
10 to 20 knots. Seas will start out at 4 to 6 feet, then end over the
weekend at 7 to 9 feet Saturday, then start to diminish Sunday.

&&

.Western Micronesia Update...
Also minor updates to western Micronesia this morning. At Koror,
increased the showers to numerous both today and tonight, also based
on model and satellite trends. Yap is isolated now, expected to be
scattered later today, and numerous tonight, so worded the forecast,
scattered showers developing for today. Little change at Chuuk.

For the Koror Waters, winds will be 10 to 15 knots through Thursday,
then 5 to 10 knots. Seas will start at 4 to 6 feet and diminish to
between 3 and 5 feet around Saturday.

For the Yap Waters, winds will be 15 to 20 knots through Thursday,
then 5 to 10 knots. Seas will start out at 5 to 7 feet, then
gradually diminish reaching 4 to 6 feet for the weekend.

For the Chuuk Waters, winds will be 10 to 20 knots through the
weekend. Seas will start out at 5 to 7 feet, and finish the weekend
at 6 to 8 feet. So Chuuk is the transition zone between the growing
and nearly hazardous seas in eastern Micronesia, and the lowering
seas in the Yap and Koror Palau Waters.

&&

.Prev discussion... /issued 536 PM ChST Tue Nov 26 2024/

Marianas Synopsis...
Conditions are breezy but mostly dry throughout the Marianas, with
fresh trade winds across the region. Surface observations at Guam
this afternoon show sustained winds at around 20 knots (23 mph) with
gusts of 30-35 knots (35-40 mph), and for Saipan, gusts up to 25
knots (29 mph). Himawari visible satellite shows partly cloudy skies
over the islands and isolated showers across the area, mainly pushing
across Guam coastal waters along a series of weak, short-lived
outflow boundaries. Numerous showers are seen east to southeast of
the Marianas, focused along a surface trough north-northwest of
Chuuk. Ipan and Ritidian buoys show 7 to 9 foot seas, while Tanapag
buoy shows 5 to 7 feet.

Discussion...
A surface trough just southeast of the Marianas will begin to pass
west of the islands overnight, increasing shower and thunderstorm
chances for Guam and Rota, but most of the showers look to remain
south of the region. As this trough shifts west of the Marianas, it
looks to gradually merge with a broad area of troughing and increased
moisture over western Micronesia, which will lift north over the
next few days in response to broad low pressure transiting the
central North Pacific. This will lead to increased showers near the
Marianas on Thursday and Friday, mainly for Guam and Rota as the
trough axis looks to shift further west of the CNMI than previous
model runs have pointed to. Additionally, there is a very sharp
north-south moisture gradient across the Marianas and the forecast
reflects this, keeping showers isolated for Saipan and Tinian
throughout the forecast period.

The main forecast concern will be a continuation of fresh trade
winds and the possibility for strong gusts, particularly near any
showers. A Small Craft Advisory is currently in effect through
Thursday afternoon, due to a combination of sustained elevated trade
winds and seas of 7 to 10 ft. Winds will likely sustain at around 20
(23 mph) knots or just below over the next few days, but higher gusts
in the mid-20s to around 30 knots (35 mph) will be frequent at times,
particularly near showers, which will contribute significantly to
choppier seas and marine conditions hazardous to small craft. Surf
and rip current risk will remain elevated for east facing reefs for
much of this week given higher trade winds and swells, with a high
risk of rip currents expected to last into the weekend.

Trade wind should begin to relax by the end of the week as the
strong subtropical ridge just east of Japan shifts eastward, allowing
the pressure gradient to relax across the Marianas and far western
Micronesia.

Marine...
Recent altimetry and scatterometry data shows combined seas around 8
to 10 feet east of the Marianas within an area of fresh to strong
trade winds. Ritidian and Ipan buoy data trends show 7 to 9 foot seas
continuing to increase this afternoon. Strong gusts may become
frequent at times especially near any showers in the area,
contributing to choppier seas. Conditions hazardous to small craft
look to prevail tonight and continue through Thursday. Winds and seas
should begin to decrease by the end of the week as the trade flow
subsides.

Eastern Micronesia...
A remnant ITCZ lingers over Eastern Micronesia, and satellite shows
areas of heavy showers developing over the Marshall Islands and over
Pohnpei State; mainly associated with surface troughs, along with
areas of moderately strong surface convergence. Also, moderate to
fresh trade winds will continue to develop over the region. Kosrae
has fair weather just for today. The surface troughs and heavier
showers should gradually move westward during the next couple of
days. Then, models indicate relatively drier weather developing
slowly for the longer term.

The marine environment will become more choppy as we move through
the week into this weekend. A trade-wind surge will bring increasing
winds and wind waves to the region. Building seas and surf could
possibly require advisories by this weekend, especially for Kosrae
where surf criteria along eastern shores is only 8 feet.

Western Micronesia...
High-end scattered showers and isolated thunderstorms are expected
for Yap and Palau through Wednesday. This is due to trade-wind
convergence over much of central and western parts of western
Micronesia. Showers are expected to increase for Thursday and
Thursday night as a trade-wind trough will move through the area and
amplify the already unstable atmosphere. Then, near the end, a much
drier pattern is anticipated as the remaining showers move westward.

Chuuk, on the other hand, will see numerous showers tonight, but
gradually see less and less showers as the week progresses. The main
source for tonight`s showers is a fairly strong trough and
convergence over Weno. The troughs that are effecting Pohnpei and
Kosrae will be what keeps Chuuk in a wet pattern this week.

Recent altimetry suggests combined seas of 6 to 8 feet over all of
western Micronesia. Winds will be gentle to fresh for the rest of the
weekend. Yap and Palau will generally see the worst of the winds in
the coming days, but gradually diminish as the week progresses. For
Chuuk on the other hand, winds are expected to stay relatively
steady through the rest of the week. Seas are expected to remain
below High Surf and Small Craft advisory conditions, however, seas
will be choppy especially near showers.

&&

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

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

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

&&

$$

Marianas Update: Montvila
Micronesia Update: Stanko