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AFDGUM

Area Forecast Discussion...UPDATED
National Weather Service Tiyan GU
833 PM ChST Thu Dec 4 2025

.Update...
Updated Kosrae`s forecast for the rest of tonight to decrease
showers from scattered to isolated. Satellite imagery has shown
decreasing cloud cover over the island and coastal waters and very
few showers are seen near or east of Kosrae to support scattered
showers through the night. A similar trend is starting to occur at
Majuro so reduced the chance of showers from 40 percent to 30
percent.

&&

.Prev discussion... /issued 634 PM ChST Thu Dec 4 2025/

Marianas Synopsis...
Satellite imagery shows mostly cloudy skies and radar imagery shows
isolated showers over the Marianas. Altimetry and buoys show seas of
6 to 7 feet.

Discussion...
Clouds are building in over the Marianas, and showers are expected
to move in over the next 24 hours for Guam and Rota as a trade-wind
trough approaches the Marianas. Once this trough passes, the
Marianas, a dry trade-wind pattern will return through at least the
middle of next week.

Marine...
Only minor changes were needed for the marine forecast. Gentle to
moderate winds are expected around the middle of next week. Seas are
expected to gradually fall for the next day or so before another
north pulse from a distant mid-latitude system moves into the
waters. This pulse is expected to raise the seas by about a foot to
6 to 8 feet. The surf will also rise because of this pulse but is
expected to remain below the 9 foot level on north and east facing
reefs.

Tropical Systems...
Invest 93W is located around 13N131E and heading westward. 93W is
continuing to consolidate as it approaches the western boarder of the
Area of Responsibility (AOR), while producing widespread showers and
isolated thunderstorms near the center. 93W is expected to move out
of the Guam AOR within the next 24 hours. For more information on
Invest 93W, see bulletins issued by the Joint Typhoon Warning Center
under WMO header ABPW10 PGTW.

Eastern Micronesia...
Satellite observations show isolated to scattered showers and
isolated thunderstorms across the region. Altimetry and buoy date
show combined seas between 6 and 8 feet across the region.

Overall, little change was made to the island forecasts. The Inter-
Tropical Convergence Zone (ITCZ) has weakened and shifted southward,
keeping the bulk of the showers away from Pohnpei, Kosrae, and
Majuro. A couple of trade-wind troughs, one near Kosrae and the
other near Majuro, will keep scattered showers in the forecast.
Showers look to become isolated by Friday night for Majuro, but look
to remain scattered through the weekend for Kosrae as the ITCZ looks
to flare up near or just south of Kosrae. Quiet conditions look to
return to all three islands early next week with isolated showers
expected.

The marine forecast continues to be the main story for impacts
across the region. Combined seas are between 6 and 8 feet, and will
remain near 6 to 8 feet through Friday. Combined seas will begin to
build late Friday night with conditions potentially becoming
hazardous to small crafts for Majuro on Saturday and for Pohnpei and
Kosrae on Sunday. No changes were made to the High Surf Advisory
today, but the advisory will likely need to be extended into the
weekend with the next northerly swell that will move in. A High Surf
Advisory may also be necessary for north facing reefs of Majuro this
weekend depending on the angle and strength of the north swell. The
Coastal Flood Statement for Majuro was upgraded to a Coastal Flood
Advisory. This was due to a combination of the King Tide and the
significant north-northeast swell. No coastal inundation is expected
for Pohnpei or Kosrae at this time.

Western Micronesia...
Satellite shows isolated showers over Yap, scattered showers over
Palau and scattered showers and isolated thunderstorms over Chuuk.
Altimetry shows seas between 3 and 5 feet for Yap and Palau and 4 to
6 feet near Chuuk, with 7 to 8 feet northeast of Weno.

The Near-Equatorial Trough (NET) remains the main player for Yap and
Palau. The trough extends southeast from Invest 93W, passing between
Yap and Palau, through a weak circulation centered northeast of
Palau to beyond the Equator near 150E. A band of convergence is seen
to the east of the NET over Chuuk. The NET and circulation will move
west over the next few days as Invest 93W continues westward.
Scattered showers remain over Palau for now, with isolated showers
currently over Yap. Showers are expected to increase through the
evening at Yap, becoming scattered later this evening, near midnight.
Instability across the area will maintain the risk of isolated
thunderstorms through tonight at Yap and through Saturday at Palau.
As the NET continues to move west, expect decreasing convection
across both Yap and Palau. Both locations can expect an extended dry
period from Saturday through the middle of next week.

For Chuuk, scattered showers and isolated thunderstorms are
currently seen across Weno associated with the band of convergence
east of the NET. This convection will continue there through the
evening, with only isolated showers expected near midnight. Like Yap
and Palau, Chuuk can then expect a dry pattern to continue through
the middle of next week.

For the marine forecast, the long-period north swell, combined with
the northeast swell and the King Tide cycle, is expected to produce
minor coastal inundation along north and east facing shores for the
next couple of days. Over the weekend, a building northeast trade
swell could prolong this inundation through Monday. This trade swell
could produce hazardous surf conditions along north facing reefs of
Weno. For Yap and Palau, another north swell, this one a bit larger
than the previous north swell, is expected to move into the region
over the weekend. This swell, combined with the trade swell and the
King Tide cycle could produce hazardous surf and coastal inundation
along north facing reefs of Yap and Palau Saturday into Sunday. All
three locations will be monitored closely over the next couple of
days for any needed advisories.

&&

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

$$

Update: Schank
Marianas: Bowsher
East Micronesia: Williams
West Micronesia: Kleeschulte