971
FXPQ50 PGUM 092026
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
626 AM ChST Sun Nov 10 2024

.Update...
The shower coverage was increased today for both Saipan/Tinian and
Guam/Rota based on Radar and Satellite trends overnight. Increasingly
moist flow is developing across the Marianas. IR satellite shows
cloudiness and showers in a large area from over the Mariana Islands
eastward to beyond 150E.

Tropical Storm Man-Yi far north of Pohnpei and Invest Area 94W over
western Chuuk State are discussed in the Tropical section below.

&&

.Tropical Systems Update...
Overnight Tropical Depression 25W was upgraded to Tropical Storm
Man-yi by JTWC and is located well north of Pohnpei and east of the
Marianas, near 16N157E. Man-yi is expected to slowly strengthen
today as it moves northwest and then turns towards the west Monday.
Forecasts then have Man-yi weakening as it near the Marianas, but it
will be something to monitor, especially as it nears the Marianas
around Tuesday. For more information on Man-yi, see bulletins issued
by JTWC under WMO header WTPN32 PGTW and the NWS under WMO header
WTPQ32 PGUM.

Invest 94W continues to move west-northwest, spreading numerous
showers and isolated thunderstorms across western Chuuk State and
eastern Yap State. Latest scatterometer and infrared satellite data
suggest 94W is centered west-southwest of Chuuk Proper near 6N149E.
The latest CIMSS tropical vorticity analysis however, shows mid-level
vorticity in the 850mb to 500mb layer is displaced slightly north of
the surface circulation, which is likely leading the variability in
the forecast track in the models. Satellite imagery shows moderate to
deep convection over a broad area covering much of western Chuuk
State and eastern Yap State. The overnight scatterometry data shows
an area of moderate to fresh winds north of the disorganized
circulation center, though gusts around 25 kt (30 mph) are possible
near heavier showers and thunderstorms. 94W was updated to medium
potential by JTWC, meaning development into a tropical cyclone is
likely but expected to occur beyond 24 hours. For more information
on Invest 94W, see bulletins issued by JTWC under WMO header ABPW10
PGTW. There is also a Special Weather Statement issued by the NWS,
which can be found under WMO header WWPQ82 PGUM.

Invest 92W was upgraded to Tropical Storm Toraji (26W) overnight as
it exited the region near 15N130E and continues to move west-
northwest, away from Micronesia, and towards the northern
Philippines. For more information on Invest 92W, see bulletins issued
by JTWC under WMO headers WTPN33 PGTW, while the NWS as issued it
last scheduled advisory on Toraji, under WMO header WTPQ33 PGUM.


&&

.Eastern Micronesia Update...
With Tropical storm Man-yi (25W) well north of Pohnpei, near
16N157E, and Invest 94W continuing to move farther west in western
Chuuk and eastern Yap state, the weather pattern from Pohnpei to
Majuro is now dominated mainly by the developing surface trough and
Inter-Tropical Convergence Zone (ITCZ) currently across the Marshall
Islands. Pohnpei and Kosrae are currently in a dry pattern with the
CIMMS MIMIC Total Precipitable Water (TPW) satellite product showing
1.6 to 1.9 inches of precipitable water, which is fairly dry for
this time of year. This is supported by satellite imagery showing
very little cloud cover this morning. Over by Majuro, numerous
showers and isolated thunderstorms are ongoing, as convection
develops along the surface trough and ITCZ, with showers becoming
more scattered in coverage near Kwajalein. As the surface trough and
ITCZ shifts west-southwest, showers will decrease around Majuro and
become more scattered in coverage this afternoon, while increasing at
Kosrae tonight and at Pohnpei by Monday, with showers becoming
numerous at times through Tuesday. The overall ITCZ pattern is
expected to support scattered showers across the region through at
least Tuesday, before the ITCZ starts to fragment.

Kosrae and Pohnpei buoys are showing seas between 4 and 5 feet this
morning. Combined seas are closer to 6 to 7 feet near Majuro.
Winds are expected to become moderate to fresh, especially across
the Marshall Islands, which, along with a slight increase in the
trade swell, will boost seas an additional one to two feet over the
next couple days, especially near Majuro, where fresh to strong
gusts accompanying heavier showers this morning will generate choppy
seas at times.

&&

.Western Micronesia Update...
Invest 94W is slowly moving west-northwest and is now west-southwest
of Chuuk Lagoon, centered near 6N149E. 94W is still disorganized but
it is generating numerous showers and isolated thunderstorms across
western Chuuk State and eastern Yap State, where gusty winds near
heavy showers and thunderstorms are likely generating choppy seas and
making travel difficult at times for the outer islands. Chuuk Lagoon
is seeing a decrease in showers as 94W pulls away and should see
showers decreasing through Monday night, before the ITCZ developing
in eastern Micronesia pushes into Chuuk around midweek. Yap and Palau
are currently experiencing fairly dry weather, but as 94W moves
west-northwest, expect unsettled weather to move into Yap Proper late
this afternoon or tonight. For Palau, light winds this afternoon may
spark some island-effect showers and thunderstorms, but kept the
potential at 30 percent as it really depends on conditions being just
right. Forecast trends continue to take 94W north of Yap as it tries
to organize into a tropical depression or even a tropical storm over
the next few days as it moves into the Philippine Sea. This path
north of Yap would help to limit the overall wind threat, but gusty
winds associated with showers and thunderstorms will still be
possible. If 94W does organize and favors a more northwest track,
this will help to limit the shower potential across Palau for most of
the week.

Babeldaob buoy shows combined seas of 2 to 4 feet near Palau, and
SOFAR buoy data southeast of Chuuk Lagoon shows 3 to 5 foot seas.
Seas will be choppier across eastern Yap and western Chuuk State
owing to locally heavy showers and associated gusty winds. These
condition may spread towards Yap Proper if 94W continues to organize
and its overall track takes it closer to the island tonight through
Monday night.

&&

.Prev discussion... /issued 618 PM ChST Sat Nov 9 2024/

Marianas Synopsis...
Latest satellite and radar imagery and showing partly cloudy skies
and isolated showers. Increasing clouds and showers approaching from
the southeast as Invest 94W approaches. Nearby buoys are indicating
seas of 4 to 6 feet.

Discussion...
The trade trough that brought scattered showers earlier today has
shifted west of the Marianas. Isolated trade showers expected for
tonight through tomorrow morning. A tropical disturbance, known as
Invest 94W from the Joint Typhoon Warning Center (JTWC), continues to
slowly develop southwest of Chuuk, centered near 6.5N and 149.5E.
This system will trek northwestward and approach the Marianas on
Sunday. The latest forecast model guidance has trended the passage of
94W further south of Guam Sunday night into Monday, possibly as a
Tropical Depression. Gusty winds and locally heavy rainfall
potentially causing flash flooding are possible, mainly across Guam
and Rota. In addition, Tropical Depression 25W (TD 25W) has developed
northwest of the Marshall Islands and could pass through the
Marianas later Tuesday into Wednesday, with another round of gusty
winds and heavy rain possible.

Marine/Surf...
Combined seas of 4 to 6 feet and moderate winds expected through
tonight. Seas and winds begin to increase tomorrow as a tropical
disturbance (Invest 94W) approaches from Chuuk State. Winds and seas
could become hazardous to small craft, especially for Guam and Rota
waters as 94W looks to pass south of the coastal waters. Winds and
seas begin to decrease beginning Monday night, but TD 25W northwest
of the Marshall Islands approaches from the east and could impact the
coastal waters beginning Tuesday night.

A moderate risk of rip currents will continue along north and
especially east facing reefs as the elevated trade swell continues. A
low risk of rip currents is expected along south and west facing
reefs. Surf and rip risk could rise beginning Sunday night as Invest
94W approaches, bumping up swell and wind waves.

Tropical Systems...
Three tropical disturbances still remain within the Area of
Responsibility (AOR). Invest 93W has been upgraded to Tropical
Depression 25W (TD 25W) by the Joint Typhoon Warning Center (JTWC).
TD 25W is currently centered near 14.1N 159.0E and is moving
northwest, away from the RMI. For more information on TD 25W, see
bulletins issued by JTWC under WMO headers WTPN32 PGTW.

Invest 92W, currently centered near 14.5N 133.2E, continues to move
west toward the northern Philippines. 92W has strengthened and has
become much better organized today, and JTWC and has upgraded it to
a Tropical Cyclone Formation Alert (TCFA). This means 92W is expected
to become a significant tropical cyclone (Tropical Depression) in 12
to 24 hours from now. For more information on Invest 92W, see
bulletins issued by JTWC under WMO headers WTPN22 PGTW.

Invest 94W is currently centered southwest of Chuuk near 6.5N 149.5E
and is moving northwest across Chuuk State toward the Marianas. 94W
remains fairly disorganized at this time, with a "low" rating by
JTWC. This means development into a tropical cyclone is unlikely
within 24 hours. For more information on Invest 94W, see bulletins
issued by JTWC under WMO header ABPW10 PGTW.

Eastern Micronesia...
Invest 94W has developed into Tropical Depression 25W, however, 25W
is now far enough northwest of Enewetak Atoll so that the threat
from heavy showers, gusty winds, and choppy seas has diminished
across the northwestern RMI. West Pohnpei State is still seeing some
activity associated from Invest 94W, roughly centered south of Chuuk.
Although, only scattered showers are farther east over Pohnpei this
evening, soon to become isolated overnight as 94W continues moving
northwest. Meanwhile, a trough on the leading edge of an Inter-
Tropical Convergence Zone (ITCZ) is moving through Majuro, leading to
scattered to numerous showers and isolated thunderstorms over Majuro
through at least Sunday, with winds becoming fresh at times. Then,
the ITCZ builds into Kosrae Monday and Pohnpei Monday night or
Tuesday. Model guidance indicates a fragmented ITCZ pattern for the
remainder of the week, keeping scattered showers in forecast.

Kosrae and Pohnpei buoys now showing seas around 5 feet this
afternoon. Combined seas are closer to 6 to 7 feet near Majuro. An
increase in trade winds and swell are expected to boost seas an
additional one to two feet over the next couple days, especially
near Majuro where fresh to strong gusts accompany heavier showers
passing through, creating choppy seas at times. Combine seas then
subside to 4 to 6 feet for the remainder of the week in response to a
decrease in trade winds and swell.

Western Micronesia...
Satellite reveals quiet conditions across much of far western
Micronesia, with spotty shower coverage across the Republic of Palau
and scattered showers near Yap Proper, associated with trailing
surface convergence southeast of JTWC`s Invest 92W. To the east,
numerous showers and isolated thunderstorms are seen spread across
much of Chuuk State extending into parts of far eastern Yap State,
associated with Invest 94W. 94W will be the primary weather concern
over western Micronesia for the coming days, but it will remain
broad, disorganized and sluggish for the remainder of the weekend.
The system will begin to organize in more earnest late Sunday night
and Monday as it shifts northwest over eastern Yap State, to the
south of the Marianas. With latest model trends, 94W could
potentially reach tropical storm strength (maximum sustained winds >
33 knots) sometime late Monday night or Tuesday as it tracks to the
north of Yap Proper. ECMWF develops 94W more quickly, keeping the
track further north where unsettled weather will be felt more
strongly across the southern Marianas with much lighter winds and
shower coverage near Yap, but the latest GFS track places the center
of 94W closer to Yap Proper, which would bring more locally heavy
showers and stronger gusts across the area. Tuesday onward, 94W looks
to move away from western Micronesia, strengthening as it moves over
the Philippine Sea.

Marine conditions remain fairly benign. Babeldaob buoy shows
combined seas of 2 to 4 feet near Palau, and SOFAR buoy data over
southern Chuuk State shows 3 to 5 foot seas. Seas will be choppier
near Chuuk for tonight and Sunday as 94W moves northwest past Chuuk
Proper, owing to locally heavy showers and associated gusty winds.

&&

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

$$

Marianas: Simpson
Micronesia: Schank