186
FXPQ50 PGUM 121758
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
358 AM ChST Sat Jul 13 2024

.Marianas Update...
Latest satellite imagery shows a few thunderstorms across the
Marianas with occasional lightning strikes seen across Saipan and
Guam`s coastal waters.

Very little change was made to the forecast. The TUTT cell
responsible for showers and thunderstorms will move westwards today
and drier conditions will move in tonight through Monday. Isolated
showers will be possible through Monday night. Precip chances still
looks to increase towards the middle of the week as a series of
troughs move across the region.

Marine and surf forecast saw minimal change overnight. Latest
altimetry still showed seas in the 2 to 4 foot range, but seas are
expected to quickly rise to 4 to 6 feet by Sunday.

&&

.Eastern Micronesia Update...
Minor changes to the forecast. Scattered to numerous showers and
isolated thunderstorms for most of the period as the ITCZ straddles
the region and multiple trade troughs and surges pass through. Heavy
downpours and gusty winds possible with stronger showers and
thunderstorms.

Combined seas of 4 to 6 feet and gentle to moderate winds expected
for Pohnpei and Kosrae. For Majuro, seas of 4 to 6 feet and moderate
winds will increase Sunday into early next week, becoming as a trade
surge pushes in, peaking on Monday. Conditions could become hazardous
to small craft, but for now, look to stay just below criteria.

&&

.Western Micronesia Update...
Minor changes to the forecast. For Chuuk, the ITCZ will straddle the
region and multiple trade troughs and surges will pass through. For
Palau and Yap, the monsoon trough and embedded disturbances will
impact the zones. Did increase shower coverage and introduce heavy
downpours and gusty wind potential for the period.

For Chuuk combined seas of 4 to 6 feet and gentle to moderate trade
winds expected. For Palau and Yap, combined seas of 3 to 5 feet and
gentle to moderate winds expected. Marine conditions will deteriorate
somewhat for Yap and especially Palau through the weekend, with seas
expected to rise 1 to 2 feet. Winds and seas could increase further
if the monsoon surge comes in stronger than expected.

&&

.Prev discussion... /issued 540 PM ChST Fri Jul 12 2024/

Marianas Synopsis...
Satellite shows partly to mostly cloudy skies and scattered showers
across the region, as well as thunderstorm activity within and east
of Guam`s coastal waters this afternoon. Some cells have collapsed
and sent some outflow boundaries over land, but the shower complex
has stayed off to the east for the most part. Ritidian and Tanapag
buoys indicate combined seas of 2 to 4 feet.

Discussion...
A tropical upper-tropospheric trough (TUTT) cell is now overhead,
and has been responsible for the thunderstorm activity as of late.
Scattered showers and isolated thunderstorms are expected to continue
through Saturday as this TUTT cell eventually drifts to the
northwest and weak trade-wind troughs move along at the surface.
Another trough looks to pass through Sunday night before a moist,
troughing pattern moves in from the south by Tuesday, bringing
unsettled weather through late week.

Marine/Surf...
Gentle to moderate winds are expected through the middle of next
week. Seas of 2 to 4 feet build to 4 to 6 feet by Sunday in response
to an increase in trade swell and winds. A moderate risk of rip
currents will continue along east facing reefs, with a low risk along
other reefs. Similar to combined seas, surf along east facing reefs is
also expected to increase slightly by Sunday.

Eastern Micronesia...
Convergent surface winds are focused along 5N to 7N across Pohnpei
and Kosrae States and the southern Marshall Islands as the ITCZ has
become better developed today. Dry weather continues over the far
northern RMI. Models indicate unstable and active weather will
continue over Eastern Micronesia thru the next few days, and the
moist weather will gradually move towards the west and northwest.
Models indicate slightly drier weather will arrive from the east and
slowly move westward next week.

Combined seas of 4 to 6 feet are expected the next couple of days,
but increasing winds and waves are expected next week, with combined
seas probably 5 to 7 feet across the region next week; even higher
winds and waves over the northern parts of the region.

Western Micronesia...
A monsoon trough stretches across Western Micronesia from a weak
circulation east of Mindanao at 8N130E, through a second weak
circulation southeast of Koror at 5N140E, then east and southeast
into southern Chuuk State.

Satellite shows heavy showers across the south parts of the trough,
and toward the Equator, with patchy areas of showers over Palau and
Yap State. Convergent easterly winds still over northern and central
Chuuk State are causing scattered showers and isolated thunderstorms.
Models indicate the monsoon trough will continue over the region and
it could gradually develop further, so that showery weather will
likely persist for this region.

Marine conditions will deteriorate somewhat. Southwest to west swell
waves and westerly surface winds will further develop during the
coming days, especially for Palau. Combined seas are expected to
build into the 4 to 6 foot range by next week for Yap and Koror.
Also, a moderate flow of easterly trade wind waves will be moving
into Chuuk State by next week.

&&

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

&&

$$

Marianas: Williams
Micronesia: Slagle