460
FXPQ50 PGUM 140752
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
552 PM ChST Sun Jul 14 2024

.Marianas Synopsis...
Moderate trades and localized trade showers are seen across the
Marianas with seas 4 to 6 feet. Expect isolated showers and
thunderstorms through tonight.

&&

.Discussion...
Isolated thunderstorms were seen across the waters today and is
expected through tonight, and showers look pretty isolated east of
the waters. For Monday and Monday night, expecting a little more
subsidence, so forecasted isolated showers without thunderstorms.
From Tuesday through Thursday, the monsoon trough is seen extending
across from Koror and Yap, reaching into the Marianas. At the same
time, a Tropical Upper Tropospheric Trough (TUTT) moves into the
area. Both GFS and ECMWF indicate a possible circulation developing
near Yap Wednesday, but after that, solutions diverge as far as
development and direction of movement. Both models show a southeast
wind with showers developing around Tuesday night. Adjusted the
previous forecast slightly, scattered showers starting Tuesday night
and ending around Thursday. Still, Friday and Saturday forecasts are
a little more uncertain. If a tropical disturbance develops near Yap,
we may see higher potential for showers over the weekend. If not,
trades push through with less shower potential.

&&

.Marine...
Gentle to moderate trades are expected to continue for the Marianas
tonight and for next few days. Starting Tuesday night, expect an
increase in showers, winds and wind waves. Easterly swell heights
are expected to see little change, but a 2 to 3 foot swell should
develop near the end of the week as west-southwest winds associated
with the monsoon trough strengthen.

&&

.Eastern Micronesia...
The Inter-Tropical Convergence Zone (ITCZ) remains fairly active
across the region, generating scattered to numerous showers and
isolated thunderstorms from the Marshall Islands to Pohnpei this
evening. In the short term, satellite imagery shows weather clearing
to the east of Kosrae so expect showers to briefly become isolated at
Kosrae tonight, before increasing again Monday as the showers south
of Majuro push westward into Kosrae. The ITCZ is expected to slowly
fragment into a series of troughs later this week as models show the
ITCZ loosing its southeast winds. This pattern will still support
showers and thunderstorms across the region, with some being locally
heavy, but showers will start to cluster more around the troughs.
Another feature that has so far played a minor role is the trade-wind
surge north of the Marshall Islands. The trade-wind surge is
currently fragmented with pockets of winds around 20 to 25 mph mainly
north of the Marshall Islands and near the Date Line. However,
models show the trade surge rebuilding across the Marshalls Monday
night into Tuesday bringing breezy conditions of 20 to 25 mph to most
of the Marshall Islands, with winds then relaxing back to the 10 to
20 mph range later in the week.

Altimetry data shows seas are 3 to 5 feet around Pohnpei and Kosrae,
and pushing up to 6 to 7 feet north of the Marshall Islands, where
winds are slightly stronger due to the trade-wind surge. As the
trade-wind surge rebuilds across the Marshalls Monday night and
Tuesday, seas are expected to build up to 9 feet with sustained
winds around 20 knots. This is just below small craft conditions of
10 feet and/or winds of 22 knots or greater, so held off on an
advisory for Majuro, but added a headline in the forecast for
Majuro`s coastal waters to highlight the potential for choppy seas
Monday night and Tuesday. Otherwise seas are expected to build a foot
at Pohnpei and Kosrae over the next few days with some slightly
stronger winds near heavier showers and thunderstorms.

&&

.Western Micronesia...
The monsoon trough extends across the region, passing just north of
the main islands of Palau then continues southeast ending near
EQ152E. The region is divided between monsoon west-southwesterly
flow, over Palau, colliding with the trade-wind pattern set up over
Yap and Chuuk. An embedded disturbance is south of Eauripik in
eastern Yap State and is helping induce diffluent flow near and east
of Palau. A decrease in shower coverage is evident on satellite, so
trimmed back shower coverage in Palau`s forecast tonight and tomorrow
morning. However, this is a brief lull and locally heavy showers
with stronger gusts are still possible with the unsettled weather
pattern in the region. Models show the potential of a north to
northwest shift of the monsoon trough over the next few days,
bringing abundant showers and thunderstorms for Palau for most of the
week and for Yap starting Monday night or Tuesday, with heavy
downpours and gusty winds expected. For Chuuk, showery weather
persists through the week due to the ITCZ pattern stretching across
from eastern Micronesia, possibly fragmenting near Chuuk late week.
Trade-winds troughs passing through the ITCZ are expected to
heighten shower and thunderstorm activity at times.

Localized effects of heavier showers will lead to choppy seas across
Palau over the next few days and for Yap state in the coming days.
Southwest to west swell waves and westerly surface winds will further
develop, allowing for seas to build to 4 to 7 feet over the next few
days, especially for Palau. Ngaraard, Babeldaob Buoy still shows
seas around 3 feet, since it is shielded from westerly waves. For
Chuuk, gentle to moderate trades with stronger gusts near showers and
seas of 4 to 6 feet are expected for the next several days.

&&

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

$$

Marianas: Hong
E. Micronesia: Schank
W. Micronesia: Cruz