349
FXPQ50 PGUM 050750
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
550 PM ChST Fri Jul 5 2024

.Marianas Synopsis...
Satellite imagery shows partly cloudy skies and isolated showers
across the Marianas this evening, with a weak trough approaching the
southern waters of Guam from the southeast. Winds are gentle to
moderate, with altimetry and buoy data showing combined seas around 3
to 5 feet.

&&

.Discussion...
Weather across the Marianas is fairly dry this evening, but a weak
trough southeast of Guam will move up into the area later tonight
and into Saturday, and then pushing west of the islands Saturday
night. Scattered showers are expected to move into Guam after
midnight and then spread northward into Rota Saturday, while model
guidance currently keeps most of the showers south of Tinian and
Saipan. Due to lack of upper-level support and the fact no lightning
as been detected within the trough by the Global Lightning Detection
(GLD) network so far today, did not mention thunderstorms in the
forecast for tonight and Saturday. As the trough moves off to the
west Saturday night, showers will decrease back down to isolated,
with partly to mostly cloudy skies through early next week as most of
the active weather features are expected to remain south of the
Marianas, occasionally clipping the Marianas around the middle of
next week.

Previous forecast have mentioned isolated thunderstorms for Sunday
and Sunday night as models shows the Tropical Upper-Tropospheric
Trough (TUTT), currently near Wake Islands, nearing the Marianas
around Sunday. Decided to keep isolated thunderstorms in the forecast
at this time, but there are signs that the risk for thunderstorms
may be decreasing. First, models are now showing no notable surface
features, such a trough near the Marianas around Sunday, which would
help to limit the development showers that could grow into
thunderstorms. Also, global models show the TUTT weakening over the
next couple of days, which also points to a diminishing risk for
thunderstorms on Sunday.

&&

.Marine...
Gentle to moderate trade winds and combined seas of 3 to 5 feet will
continue through at least Wednesday. Through Saturday, most of
showers within the coastal waters will be within Guam and Rota
waters due to a passing trade-wind trough currently southeast of the
Marianas. There is the potential for isolated thunderstorms Sunday
as the Tropical Upper-Tropospheric Trough (TUTT) east of Wake Island
slowly drifts westward towards the Marianas and is expected be near
the Marianas around Sunday. There are signs that the potential for
isolated thunderstorms may be decreasing, and this may be reflected
in future forecasts as the exact timing and strength of the TUTT and
any surface features becomes more certain

&&

.Eastern Micronesia...
Expect scattered showers and isolated thunderstorms tonight for
Majuro. Active weather near Majuro will then dissipate as divergence
aloft shifts west. A trade-wind trough near Kosrae was producing
showers for Kosrae this morning, and has not moved much. The near-
equatorial trough has extended further east to Pohnpei and maybe even
slightly further east to near Kosrae. Scattered showers and isolated
thunderstorms are expected through the weekend at both Pohnpei and
Kosrae and possibly until the middle of next week.

Altimetry reported 3 to 5 ft near Pohnpei and Kosrae. Gentle to
moderate trade winds are expected through out the forecast period.
Sightly elevated winds are expected tonight at Majuro as the
weakening convective system moves across their waters. Seas are
expected to increase by 1 to 2 feet starting early next week through
at least middle of next week.

&&

.Western Micronesia...
For Chuuk, expect scattered showers tonight as a trade-wind trough
crosses the island. Also an upper-level low is moving across and may
fire off some thunderstorms. Tomorrow`s weather looks better for
Chuuk, so went with isolated showers, as models predict a flattening
out of the trough by tomorrow. Latest visible satellite shows spotty
showers across Koror and Yap with a near-equatorial trough or
possible weak circulation to the east of Koror. Expect scattered
showers and isolated thunderstorms tonight. By tomorrow expect
isolated showers as divergence aloft moves out of the region. A few
upticks in showers are expected in the following days, but nothing
significant, will possibly see some island convection showers and
thunderstorms with light and variable winds forecasted for the next
few days.

Altimetry reported benign seas of 2 to 4 feet near Palau and
Yap. Expect light and variable winds for Palau and Yap and light to
gentle for Chuuk through out the forecast period. Seas for Chuuk are
expected to increase by 1 to 2 feet starting early next week, but for
Palau and Yap, seas are expected to remain at 2 to 3 feet.

&&

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

$$

Marianas: Schank
Micronesia: Hong