870
FXPQ50 PGUM 021925
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
525 AM ChST Thu Jul 3 2025

.Marianas Update...
Widely scattered showers are expected to stay mainly over the
waters, with only isolated showers coming on shore. After this
morning, a ridge building in will cause somewhat dry weather through
Friday night. Then, the monsoon is expected to draw near and could
bring scattered showers to the Marianas. Refreshed the winds, which
was merely cosmetic. The big change was to delay the scattered
showers from Thursday into Friday. Radar and satellite look nearly
scattered right now, but of course this is the nightly peak of the
diurnal cycle. So, snuck in a reference to morning scattered showers
in the coastal.

&&

.Tropical systems...
Tropical Storm 04W is currently near 26.5N and 146.1E, and was moving
northwestward, or away from the islands. The only effect we could see
from it maybe some north swell, and probably rather little of that.
Keep your eyes peeled in the long term though. We`re moving into the
more active part of the season.

&&

.Eastern Micronesia...
Isolated to scattered showers are seen across the region. The main
change was to decrease shower coverage slightly from 50% to 40% and
start Kosrae and Pohnpei with isolated showers. Guidance has been
overdoing the building ITCZ so far, but surface convergence should
still lead to scattered showers in the afternoon.

No changes were made to the marine forecast. Combined seas of 4 to 6
feet look to continue through the week.

&&

.Western Micronesia...
A lull in showers and thunderstorms is seen across Palau and Yap.
Guidance shows little development across Yap today and showers stay
just west of Palau as well. Shower coverage was dropped to isolated
for both. PoPs were also lowered for for Chuuk with the latest
guidance showing less shower coverage today.

No changes were made to the marine forecast.

&&

.Prev discussion... /issued 524 PM ChST Wed Jul 2 2025/

Marianas Synopsis...
Gentle to moderate southerlies prevail. Satellite imagery and Doppler
radar indicate some island-generated showers trickling over the
northern of the islands. The buoys indicate seas are around 3 feet.

Discussion...
While Tropical Depression 04W is well north-northeast of Maug and
has exited our region to the northwest, it continues to influence
the regional weather, dragging the monsoon trough to the north along
with it. In addition to an upper-level trough shifting northwards as
well, this will allow low-end scattered showers and thunderstorms to
diminish tonight through Friday, as a surface ridge builds into the
region. Winds will also shift more to the south and diminish
slightly, only to pick up once again during the weekend. At this
time, heavy rainfall is not expected for the remainder of the week.

Marine...
Combined seas of 3 to 4 ft will persist as such for much of the
forecast period. A moderate risk of rip currents is expected along
east facing reefs of the Marianas for much of the week, with
potential for the risk to become moderate along west facing reefs
once a secondary westerly swell arrives by early next week.

Tropical systems...
Tropical Depression 04W, is centered near 25N147E, moving north to
northwest at 9 mph. At this time, maximum sustained winds are 35 mph
near the center. 04W is forecast to intensify through tonight,
possibly becoming a tropical storm by later tonight. No direct
impacts are expected to the Marianas or Micronesia from this storm.

Eastern Micronesia...
The well-developed ITCZ is producing scattered showers and some
thunderstorms across much of eastern Micronesia. The Probability of
Precipitation (PoPs) were increased to 40-50 percent through Thursday
night to reflect the magnitude of the showers. As this band of
showers and thunderstorms will gradually decrease as the ITCZ looks
to diminish, and pleasant weather is anticipated to return near the
weekend. Altimetry shows combined seas of 4 to 6 feet. Winds are
expected to remain gentle to moderate through the weekend, with
occasionally fresh to possibly strong gusts with heavier convection.

Western Micronesia...
The monsoon flow is slowly weakening over Palau, but weak troughing
within the flow could still result in scattered showers and isolated
thunderstorms through the end of the week. A surface ridge east of
Yap looks to creep west and push the edge of the monsoon flow to the
northwest Yap, with generally isolated to low-end scattered showers
expected through the end of the week. The ridge will continue
creeping west over the weekend, with mainly isolated showers expected
for both Yap and Palau. However, early next week the ridge looks to
break down over the region, with a slow return to a wetter, monsoon-
like pattern.

Outside of gusty winds and choppy seas near heavier showers and
thunderstorms for Palau tonight and Thursday, fairly benign marine
conditions expected, with seas 3 to 4 feet and light to gentle winds
diminishing slightly over the coming days as the monsoon swell
decreases and surface ridging builds in. Early next week, a longer-
period northwest swell generated by a possible distant tropical
cyclone developing northeast of the Philippines could build into the
region, increasing seas ans surf.

For Chuuk, a surface trough lifting northwest along the leading edge
of a building ITCZ is currently passing. High-end scattered showers
and isolated thunderstorms are expected through Thursday as the
aforementioned features pass through. While coverage looks to
diminish beyond Thursday as the trough pushes away and the ITCZ
diminishes, still expecting scattered showers and isolated
thunderstorms into the weekend as subtle surface features pass
through and weak east-southeast flow linger.

Gentle to moderate winds are expected through Thursday. Fresh to
potentially strong gusts are possible near heavier showers and
thunderstorms as well. Winds look become light to gentle by Friday as
the trough pushes west. Seas of 4 to 6 feet will be possible through
Thursday night with the disturbance pushing through, then lowering
by around 2 feet over the weekend into next week.

&&

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

$$

Marianas: Stanko
East/West Micronesia: Williams