337
FXPQ50 PGUM 301927
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
527 AM ChST Fri Jul 31 2026

.Marianas Update...
Retained the zone split, which seemed like a good idea. Just added a
morning versus afternoon split for Guam. Kept the showers isolated
for this morning, since they are now, then ramped them up in the
afternoon. The surge is now visible south of Guam, but for the
morning at least, it`s still to the south.

&&

.Marine...
In 48 hours or so gale force gusts will commence in the marine
forecast. Therefore put out a gale watch for Guam Waters. CNMI Waters
may need something similar, but it`s a little too early. Looks like
we will probably fall just short of a hazardous seas warning, so
the gale watch will likely be upgraded, whether to a gale warning or
a small craft advisory we can`t be sure at this time.

&&

.Fire weather...
Until the showers get here, the KBDI keeps climbing, and is now at
329. If we don`t reach 0.20 inches before midnight tonight, it will
go up even higher.

&&

.Tropical Systems...
Super Typhoon Dolphin is near 17.9N and 162.8E. It has been moving
west-northwest, and is expected to pass between Wake and the northern
CNMI, potentially passing near Iwo To. Dolphin seems to have stopped
intensifying for the moment.

Invest Area 94W remains at a rating of sub-low for its potential for
formation into a tropical cyclone. It continues to slowly move west.

For more information on both of these, please refer to:
Significant Tropical Weather Advisory issued by the Joint Typhoon
Warning Center under WMO header ABPW10 PGTW.
Tropical Cyclone Warning issued by the Joint Typhoon Warning Center
under WMO header WTPN31 PGTW
Tropical Cyclone Public Advisory issued by the National Weather
Service under WMO header WTPQ31 PGUM.

&&

.Eastern Micronesia Update...
Showers at Majuro have thinned out, so lowered them from numerous to
scattered. As Dolphin continues to move westward, Majuro should end
up farther and farther from the zone of convergence. Everything else
was fine and no other updates were needed. The Small Craft Advisories
looked particularly appropriate.

&&

.Western Micronesia Update...
The forecasts for Western Micronesia looked fine as they were. Thought
about cutting Yap down to isolated, but held on to low-end scattered
in the end as the showers could continue to build over toward them.
Did not issue a Small Craft Advisory for Chuuk at this time, will wait
and see if winds support it later, so everything in the current
package was okay.

&&

.Prev discussion... /issued 713 PM ChST Thu Jul 30 2026/

Marianas Synopsis...
Satellite imagery indicates mostly cloudy skies and scattered
showers across the Marianas with some remnant thunderstorms in Guam`s
northwestern coastal waters. Buoy data supports combined seas of 2
to 4 ft.

Discussion...
A col located to the northeast will bring light to variable winds
over the Marianas starting tonight, lifting north-northwest and
departing the region by Saturday afternoon. A monsoon pattern that is
currently south of the Marianas will move northward over Guam on
Friday, bringing moderate to breezy southwest to west winds and a 40
percent chance of showers through the rest of the forecast period.
The CNMI can expect this regime starting Saturday afternoon, so light
and variable winds and isolated showers are in store until then.
Island-effect showers are a possibility, but the size of these
islands tend to be too small to cause substantial rainfall. The
forecast zones were split into two to accommodate for the timing and
spatial differences of the monsoon pattern. Isolated thunderstorms
associated with a typically wet monsoon pattern should not be ruled
out by the end of the weekend and through next week.

Marine...
The speed convergence associated with the surrounding southwest
quadrant of the col to the northeast is allowing for scattered
showers over the Marianas coastal waters, with isolated
thunderstorms concentrated in Guam`s northern to northwestern
coastal waters and outside of the western coastal waters of Rota. The
forecast indicates these thunderstorms for Guam tonight, but may be
re-evaluated for the CNMI as the evening continues.

Buoy data supports combined seas of 2 to 4 ft. There will be light
to gentle southerlies for Guam coastal waters and light variable
winds for the CNMI coastal waters tonight. Distant Super Typhoon
Dolphin is generating a long-period easterly swell that will reach
the Marianas Friday night, shifting northerly by midweek. Therefore,
there is a moderate risk of rip currents along east-facing reefs at
least through the weekend. A monsoon pattern will introduce
increasing southwest to west winds and a building southwesterly swell
by the end of the weekend, which will most likely induce hazardous
sea conditions to small craft vessels. Marine interests should
monitor the forecast over the coming days as sea conditions will
start to deteriorate by early next week.

Tropical Systems...
Super Typhoon Dolphin seems to have peaked as it moves northwest.
STY Dolphin is centered near 16.7N 165.2E, moving west- northwest at
13 mph. Maximum sustained winds have decreased slightly to 160 mph as
Dolphin moves southwest of Wake Island. Latest satellite imagery
displays a well defined eye, showing that Dolphin made a splendid
recovery from its eyewall replacement cycle. STY Dolphin remains in
an area of favorable conditions, however, it appears that it will
remain around this intensity for the next couple of days. STY Dolphin
is then expected to weaken starting Saturday through the beginning
of next week.

For more information on STY Dolphin, please refer to bulletins issued
by the Joint Typhoon Warning Center under WMO header WTPN31 PGTW and
by the National Weather Service under WMO header WTPQ31 PGUM.

A weak circulation, Invest 94W, remains southwest of Guam, northeast
of Yap Proper, centered near 12.8N 140.3E. 94W is drifting slowly
west, with little change in intensity. Invest 94W is helping to fuel
a weak monsoon surge across Palau and far western Yap State. As 94W
continues to slowly drift west, it will maintain enhanced winds to
the south of the monsoon trough over Palau and Yap Proper. Little to
no development is expected with Invest 94W.

Eastern Micronesia...
The monsoon trough remains active across eastern Micronesia. STY
Dolphin is producing a monsoon surge across the region, producing
scattered to numerous showers and isolated thunderstorms across
Pohnpei and Majuro, with scattered showers and isolated thunderstorms
across Kosrae. As Dolphin continues to move west-northwest, it will
drag the monsoon trough farther north. This will allow clearing and
drier conditions to move into Kosrae Friday and Pohnpei Saturday
evening. Majuro, however, looks to remain in a wetter pattern a bit
longer, with the drier pattern moving into the Marshalls early next
week.

The monsoon surge is now producing fresh to strong winds, making
seas choppy and producing conditions hazardous to small craft
operations west of the Marshalls. Therefore, a Small Craft Advisory
was issued for Pohnpei through Saturday night and for Kosrae through
Friday night. Seas are expected to exceed 10 feet at Kosrae through
Friday night and Pohnpei through Saturday night due to a building
north to northeast swell from STY Dolphin along with a continuing
southeast swell and wind waves, especially over the northern waters.

Western Micronesia...
A monsoon pattern persists across region over the next several days.
The monsoon trough lies just north of western Micronesia, anchored
between Invest 94W (north of Yap Proper) and Super Typhoon Dolphin
(southwest of Wake Island). Invest 94W is focusing showers west and
north of Palau and Yap this evening, with another area showers and a
few thunderstorms across Chuuk State, at the tail end of the
developing monsoon surge trailing STY Dolphin. The western half of
the monsoon trough will be semi-stationary north of Yap and Palau
through the next few days, keeping scattered showers through early
next week mainly across Yap, with isolated to scattered showers
across Palau. The eastern half of the monsoon trough looks to shift
slightly north, leading to drier conditions for Chuuk this weekend
and early next week.

Combined seas are between 3 to 5 feet, increasing to 6 feet east of
Chuuk Lagoon. Seas are expected to become increasingly choppy this
weekend for Chuuk, and early next week for Palau and Yap, as the west
to southwest monsoon swell builds, wind waves increase, and swell
arrives from the northeast, emanating from STY Dolphin. A Small Craft
Advisory may be warranted for Chuuk by Saturday night and for Yap
Monday or Tuesday. Additionally, the long-period swell from STY
Dolphin arrives late tonight at Chuuk, primarily elevating surf along
north and east-facing reefs over the next several days.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...None.
MP...None.
Marianas Waters...Gale Watch from Sunday morning through late Tuesday night for
     PMZ151.

&&

$$


Marianas/East and West Micronesia/Tropical Update: Stanko
Marianas: Mesa
East Micronesia/Tropical: Kleeschulte
West Micronesia: Cruz