689
FXPQ50 PGUM 230659
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
459 PM ChST Sun Jun 23 2024

.Marianas Synopsis...
Satellite imagery is showing partly cloudy skies and isolated showers
across the Marianas. Increasing clouds and showers are approaching
from the east. Latest altimetry passes and Ritidian buoy are showing
seas of 3 to 5 feet.

&&

.Discussion...
The isolated trade-wind regime continues this evening across the
Marianas. By later tonight into Monday, a surface trough and surge
in trade winds will pass through the region, bringing scattered
showers to Guam and Rota, along with a potential for isolated
thunderstorms for Guam. While showers increase for Tinian and
Saipan, coverage looks to stay isolated. Another trough looks to clip
the region Wednesday into Wednesday night, bringing a chance of
showers and slight chance of thunderstorms for Guam. A TUTT cell,
currently to the south of Wake Island, looks to approach the Marianas
by late week. While model guidance is not showing a substantial
increase in shower potential, have introduced a slight chance of
thunderstorms for Thursday and Friday across the Marianas as the TUTT
cell passes north then west of the Marianas. Into the weekend,
deterministic and ensemble guidance trending towards a monsoon
trough emerging from Asia and possibly creeping up towards the
Marianas. This could signal that start of wet season for the
Marianas.

&&

.Marine/Surf...
Moderate trade winds with seas 3 to 5 feet this afternoon and
evening. Winds and seas begin to increase later tonight as a surge in
trade winds and trade swell arrive. Moderate to fresh winds expected
through the workweek, peaking on Monday and Tuesday. Seas build to 5
to 7 feet for Tuesday and Wednesday, then look to drop about a foot
for late week.

Surf looks to rise slightly on Monday as the trade swell increases
and a background northerly swell arrives. The rip risk looks to
become moderate along north facing reefs, but likely staying at
moderate along east facing reefs and low along south and west facing
reefs.

&&

.Eastern Micronesia and Chuuk...
Satellite this afternoon shows a couple of weak trade-wind troughs
within the region. The first trough is generating weak to moderate
convection south of Majuro, while the second between Kosrae and
Pohnpei is generating pockets of moderate to deep convection north of
both islands. The third trough between Pohnpei and Chuuk is
generating pockets of moderate to deep convection around 100 miles
south-southeast of Chuuk State. Model analysis this afternoon show an
Inter-Tropical Convergence Zone (ITCZ) building westward to Majuro
by Monday, then to Kosrae and Pohnpei on Tuesday, and Chuuk around
the middle of the week, with bouts of showers expected on all the
islands through mid week. Models then show the ITCZ fragmenting into
individual trade-wind troughs before dissipating toward the latter
part of the week, with another ITCZ building from the International
Date Line early this weekend.

Gentle to moderate trades and seas of 3 to 5 feet are expected
to rise around a foot due to surge in east trade swell on Monday
night, then arrive at Kosrae, Pohnpei, and Chuuk around the middle of
the week. Seas will fall around a foot in the latter part of the work
week into the weekend. Altimetry passes this afternoon show combined
seas between 3 and 5 feet at Majuro, Kosrae and Pohnpei and 2 to 3
feet at Chuuk.

.Western Micronesia for Palau and Yap...
A simmering weather pattern is in store for Palau and Yap this week,
with shower coverage increasing significantly as a tropical
disturbance moves in by the middle of the week. Lack of agreement
between various forms of model guidance, and poor initialization with
recent satellite imagery, indicate great uncertainty in shower and
wind potentials in the coming week as this disturbance moves across.
As of now, this feature is expected to be washed away by stronger
trades to allow another potential disturbance to form before the next
weekend.

Combined seas of 3 to 4 feet are expected to increase another 2 feet
by the midweek, followed by another period of diminishing sea heights
during the weekend.

&&

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

&&

$$

Marianas: Slagle
Eastern Micronesia: Kelly
Western Micronesia: Montvila