649
FXPQ50 PGUM 042021
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
621 AM ChST Fri Dec 5 2025

.Marianas Update...
Scattered showers and isolated thunderstorms are developing around
Guam and surrounding coastal waters as a weak trade-wind trough
passes just south of Guam. The rest of the Marianas experience dry
weather. Once the trough moves off to the west later today, this
drier weather will extend into Guam and continue across the Marianas
through the weekend and into next week, with winds around 10 to 15
mph.

Buoy data indicates seas are 5 to 6 feet, supported by the elevated
trade swell and slowly subsiding longer period northeast swell, with
gentle to moderate winds across the region. Another pulse of
northerly swell this weekend, along with a slight increase in the
trade swell will help to push seas up to 6 to 8 feet around Saturday.
Surf will build along north facing reefs and there is the potential
that surf will reach hazardous levels of 9 feet and generate a high
risk of rip currents, but wave model guidance continues to keep surf
just below 9 feet. Will continue to monitor if this trend continues
today or if models start to favor a slightly stronger northerly
swell.

&&

.Tropical Systems Update...

Invest 93W continues to move west-southwest and is currently near
11N128E, outside of WFO Guam`s Area of Responsibility (AOR).
Satellite and ASCAT analysis continue to support that the low-level
circulation of 93W is still fairly disorganized, with the strongest
winds not associated with the circulation but the strong winds (20 -
30 kt) associated with the cold front to the north, and the shear
line extending off the cold front and into the Philippines. 93W is
still expected to slowly consolidate as it moves towards the
Phillipines and interacts with the shear line. For more information
on Invest 93W, see bulletins issued by the Joint Typhoon Warning
Center under WMO header ABPW10 PGTW.

&&

.Eastern Micronesia Update...
Satellite imagery shows a dry trade-wind pattern across the region
with some pockets of convection south of Kosrae and Majuro this
morning. Model guidance still supports scattered showers around
Kosrae tonight and into Sunday, but when comparing the ECMWF and GFS
to current satellite imagery, it appears models are slightly
overdoing convection along troughs and any weak convergence that is
moving through the region. Did decrease the chance of showers at
Kosrae tonight from 50 percent to 40 percent to begin this downward
trend, but will continue to monitor if this trend continues today
before making additional changes to the forecast.

The main challenge remains the marine forecast for the region.
Limited altimetry data shows combined seas are between 6 and 8 feet
across most of the region south of 10, with seas pushing up to 10 ft
north of 10N where trade-winds have been elevated. Buoy data near
Pohnpei shows seas are around 5 to 6 feet along the northern point
of Pohnpei, and have trend slightly downward over night, suggesting
the mixture of the primary trade swell and secondary northerly swell
is subsiding slightly. The High Surf Advisory expires later today and
it looks like there will be a brief period (tonight and Saturday)
that surf will drop below 9 feet along north facing reefs of Pohnpei
and Kosrae, and 8 feet along east facing reefs of Kosrae. However,
combined seas will begin to build again around Saturday as another
pulse of northerly swell moves into the region and the primary trade
swell remains elevated, with seas potentially become hazardous to
small crafts for Majuro on Saturday and for Pohnpei and Kosrae on
Sunday. The question now should the High Surf Advisory be extended to
cover the rebuilding of surf or allow to expire and then reissued
when conditions return? It is also possible that the High Surf
Advisory will be extended to north facing reefs of Majuro this
weekend depending on the angle and strength of the north swell. Day
time observations should help to gauge current surf conditions
hopefully provide better timing of when surf will likely become
hazardous again to help make a decision to expire the High Surf
Advisory or expire and reissue for conditions. The Coastal Flood
Advisory for Majuro remains in effect through Saturday afternoon due
to a combination of the King Tide and the significant north-
northeast swell.

&&

.Western Micronesia Update...
Satellite imagery this morning shows drier conditions across Palau,
Yap and Chuuk this morning as most of the convection is near the
equator, along the southern edge of the NET, or near and west of the
Marianas. Overall, a drier pattern is expected across Palau, Yap and
Chuuk through the weekend and into next week as the NET shifts
westward and out of the region as it follow Invest 93W, though as
a weak trade-wind trough south of Guam shifts westward, Yap may see
some scattered showers tonight.

For the marine forecast, little has changed overnight. 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 of Chuuk 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.

&&

.Prev discussion... /issued 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.
&&

$$


Marianas/East and West Micronesia/Tropical Update: Schank
Update: Schank
Marianas: Bowsher
East Micronesia: Williams
West Micronesia: Kleeschulte