NWS Guam wrote its last area forecast discussion before the first event at Sep 8, 7:58 PM UTC, 6 hours 2 minutes earlier.
Area forecast discussion, Sep 8, 7:58 PM UTC, 6 hours 2 minutes before
Area Forecast Discussion
National Weather Service Tiyan GU
558 AM ChST Mon Sep 9 2024
.Marianas Update...
The overall forecast trend remains on track. Widespread locally heavy
rainfall and isolated thunderstorms tonight through at least
Thursday as Invest 95W passes through the region, and a robust south
to southwest flow sets up in its wake by the latter half of the
workweek.
Winds and seas will build beginning later today as Invest 95W
approaches and likely become hazardous to small craft by tonight and
continue for much of the wees 95W passes through the region. Winds
look to become fresh to strong with near gale to possibly gale force
gusts and seas look to become 7 to 11 feet. A Small Craft Advisory
has been issued beginning tonight and continuing through at least
Thursday.
Surf will increase as Invest 95W passes through and the rip risk
will likely become high along east facing reefs tomorrow. Surf and
rip current risk looks to stay elevated for most of the week,
possibly becoming hazardous along south and west facing reefs.
&&
.Hydrology Update...
While uncertainty remains on the overall development and strength of
95W as it passes through the region, confidence remains high for
heavy rainfall potential and have issued a Flash Flood Watch in
effect this evening and continuing through at least Thursday.
&&
.Tropical Systems Update...
While Invest 94W begins to depart the Area of Responsibility today
on its approach towards China, Invest 95W continues to churn
northwest towards the Marianas and away from Weno, Chuuk. Latest
guidance continues to indicate that the system will remain fairly
weak as it treks through the Marianas, with passage near Guam and/or
Rota favored. Invest 95W could pass through the Marianas as a
tropical depression, though the possibility of a minimal tropical
storm does exist but unlikely.
&&
Only minor edits made to the forecast. Pohnpei continues to see quiet
trade wind conditions this morning as Invest 95W, now located near
9N151E, moves northwest well away from the area. Latest satellite
imagery shows areas of scattered showers building to the south of
Kosrae and Majuro within a developing ITCZ-like pattern, which is
expected to linger for much of the week. Kosrae can expect to see
increasing showers today lasting for the next few days, spreading
westward to Pohnpei by Wednesday as a trough within the ITCZ
propagates westward. Models support an ITCZ lingering over the
southern RMI for much of the week, and Majuro can expect to see
scattered showers into next weekend.
Pohnpei buoy shows 3 to 5 foot combined seas while Kosrae buoy is
showing 4 to 6 feet. Light to gentle winds continue for Pohnpei and
Kosrae, but gentle to moderate winds are expected for Majuro for at
least the first half of this week. The southeast swell looks to
increase for Pohnpei slightly by Tuesday, but seas look to remain at
or below 6 feet for the next several days.
&&
Only minor edits made to the forecast. Showers are increasing over
Chuuk State this morning as Invest 95W pulls away to the northwest,
with showers becoming numerous to widespread and heavy at times today
through Tuesday, along with gusty winds. The overnight scatterometry
shows areas of southwesterly to southerly 15 to 22 knot winds within
the approaching showers to the south of Chuuk. Gusts may occasionally
reach near gale-force within the heaviest convection, especially
today and tonight. More information can be found in the Special
Weather Statement (SPS) issued for Chuuk, under the WMO header
WWPQ82. Seasonal off-and-on showers should resume for Chuuk for the
latter half of this week, after 95W has fully exited the region.
Yap and Palau can expect patchy, low-end scattered showers today as
westerly winds increase. Latest satellite shows increasing showers
to the north and south of Yap, and south of Palau. Showers and
thunderstorm potential will increase tonight into Tuesday as 95W
approaches near the Marianas, before a fresh to strong monsoon flow
sets up during the mid-week into the weekend. Showers look to become
numerous to widespread and heavy at times, mainly Wednesday night
through Friday. The general public must continue follow weather
forecasts as various agencies continue to watch the development of
this system.
Babeldaob buoy shows combined seas of 2 to 3 feet, and light to
gentle flow will persist near Palau and Yap for today and tomorrow,
followed by a slow increase that may eventually produce seas nearing
10 feet and fresh to strong winds in the second half of the week.
Meanwhile at Chuuk, 4 to 6 foot seas are expected today through
Tuesday, coming down to 3 to 5 feet heading into the latter half of
the week.
&&
.Prev discussion... /issued 543 PM ChST Sun Sep 8 2024/
Marianas Synopsis...
Satellite and radar observations show scattered showers across the
Marianas. Ritidian and Tanapag buoys show combined seas between 2 to
4 feet.
Discussion...
Minimal changes were made to this forecast package. A slight increase
in PoPs were made for the Monday night and Tuesday periods to 70
percent instead of 60 percent. This remains in the numerous category.
The other change was adding more detail to the wind forecast. Period
of calmer winds will be possible for Guam and Rota Tuesday night
into Wednesday as the circulation moves nearby. For Saipan and
Tinian, breezy conditions will be possible through the week. Trends
continue to show minimal intensification with Invest 95W as it
approaches the Marianas. See the tropical systems discussion for more
details. Heavy rainfall will be possible Tuesday through Friday, see
hydrology section for more details.
Marine...
Slight changes were made to the Marine forecast. Combined seas were
increased some using a blend of the ECwave and GFSwave. This blend
was weights 80% to the EC and 20% to the GFS. This would suggest
combined seas approaching 10 ft for the coastal waters north of
Saipan towards the middle of the week. Seas could become hazardous to
small craft. Surf could meet advisory criteria for south facing reefs
as the swell turns southeasterly around Wednesday. A moderate risk
for rip currents will prevail for east facing reefs this week and
will include south facing reefs beginning Monday.
Tropical Systems...
Satellite and surface analysis show a weak circulation, Invest 94W,
is centered near 25N135E. 94W is moving slowly west-northwest.
Invest 94W is expected to make a turn toward the northwest over the
next couple of days, moving north of 25N by Monday morning. The
potential for 94W to develop into a significant tropical cyclone
within the next 24 hours remains low.
Invest 95W is centered near 9N151E. Invest 95W has moved west-
northwest over the past 24 hours, but looks to make a turn toward the
northwest over the next day or two. This system is expected to
slowly strengthen over the next few days. The Joint Typhoon Warning
Center rates the potential of 95W becoming a significant tropical
cyclone over the next 24 hours as medium. It is possible that Invest
95W will pass through the Marianas sometime between Tuesday afternoon
to Thursday morning. However, latest guidance indicates that the
system will remain fairly weak, likely a tropical depression, though
the possibility of a minimal tropical storm does exist, though not
expected at this time.
For more information on Invest 94W and 95W, see bulletins issued by
JTWC under WMO header ABPW10 PGWT.
Hydrology...
Models still show very heavy rainfall for the Marianas this week. 4
to 8 inches of rain will be possible Monday night through Friday.
Models have begun to converge on a track near Guam or to the north
across the CNMI. Heavy rainfall will remain possible for Guam and the
Northern Marianas despite a more northerly trend in the forecast. As
the system moves off to the northwest towards the end of the week,
locally heavy rainfall will remain possible as showers and
thunderstorms stream northward into the system.
Localized flooding will be possible in low-lying and poor drainage
areas, while flash flooding could also be possible in areas of
heaviest rainfall. This developing situation will continue to be
monitored closely and a flash flood watch may be issued if conditions
warrant.
Eastern Micronesia...
A dry trade-wind pattern is in place across eastern Micronesia this
afternoon, resulting in only partly cloudy skies and isolated
showers. For Majuro, a weak ITCZ (Inter-Tropical Convergence Zone) is
seen crossing the Date Line into the western Marshall Islands near
9N. There is also a trade-wind trough seen right along the Date Line.
These two features look to interact to bring scattered showers and
isolated thunderstorms to Majuro Monday morning. As the trough moves
west, it looks to strengthen the ITCZ and drag it westward, resulting
in increased convection for Kosrae Monday night and Pohnpei Tuesday
night. A dry pattern then looks to return to the region near the end
of the week, continuing through the weekend for Pohnpei and Kosrae,
and into Saturday for Majuro. Another trade-wind trough looks to
cross the Date Line and move into the Marshalls over the weekend,
bringing increased convection to Majuro Saturday night into Sunday.
Not much happening in the marine environment. Seas look to remain at
or below 6 feet for the next several days. Light to gentle winds are
on tap for the region through the week, with Majuro seeing
occasional moderate winds during the first half of the week.
Western Micronesia...
The aforementioned Invest 95W remains to be the main weather concern
for Chuuk through much of the week, now located just north of
Fananu. Chuuk's forecast remains largely unchanged, with only a
slight uptick in shower coverage and winds for tonight. Gusts may
occasionally reach near gale-force within the heaviest convection,
especially Monday and Monday night. More information can be found in
the Special Weather Statement (SPS) issued for Chuuk, under the WMO
header WWPQ82. After the system exits Chuuk State before the middle
of the week, seasonal on-and-off showers will return.
Palau and Yap will encounter patchy showers as winds become more
westerly. Strong influence by a passing 95W will bring showery
weather and increasing winds for much of next week. At this time, 95W
is not likely to bring significant wind threats to Yap and Palau, but
fresh to strong monsoonal flow is expected during the second half of
the week. The general public must continue follow weather forecasts
as various agencies continue to watch the development of this system.
Combined seas of 2 to 4 feet will persist near Palau and Yap for the
next few days, followed by a slow increase that may eventually
produce seas nearing 10 feet in the second half of the week.
Meanwhile at Chuuk, 4 to 6 foot seas may increase by another foot
during the passage of Invest 95W.
&&
.GUM WATCHES/WARNINGS/ADVISORIES...
GU...Flood Watch from this evening through Thursday afternoon for
GUZ001.
MP...Flood Watch from this evening through Thursday afternoon for
MPZ001>003.
Marianas Waters...Small Craft Advisory from 6 PM this evening to 6 PM ChST Thursday
for PMZ151>154.
&&
Marianas: Slagle/Williams
Micronesia: Decou/Kleeschulte/Montvila