FROM: NWS GUM
AREA: NWS GUM County Warning Area
SENT: 2026-07-29T08:15:00+00:00
Area Forecast Discussion: NWS GUM
000
FXPQ50 PGUM 290815
AFDGUM
Area Forecast Discussion
National Weather Service Tiyan GU
615 PM ChST Wed Jul 29 2026
.Marianas Synopsis…
Light to gentle southeasterlies prevail across the region. Satellite
imagery and Doppler radar indicate a few lines of showers crossing
Guam and Tinian waters. Buoys show seas are around 3 feet.
&&
.Discussion…
Newly-formed Invest 93W is a very weak embedded monsoon disturbance
well west of the Marianas, which is expected to induce low-end
scattered showers tonight. Mostly dry conditions will return
thereafter as winds remain light, followed by a monsoon surge
developing across the region beginning this weekend. Said monsoon
surge will introduce southwesterly to westerly winds and a wet
pattern coming into next week, with winds likely to keep increasing
as Typhoon Dolphin (12W) moves between the far northern CNMI and
Wake Island.
&&
.Marine…
Light easterlies will slowly turn to the south and increase over
the next few days, becoming straight west come Friday night as a
monsoon regime ensues. Winds will then turn west on Friday and
gradually increase through the weekend. Combined seas of 3 to 4
feet are expected to continue through Thursday, followed by the
arrival of an easterly swell generated by distant Typhoon Dolphin
and strengthening westerly swells. By the weekend, the aforementioned
monsoonal regime is likely to introduce sea conditions hazardous
to small craft. A low risk of rip currents is expected along all reefs
of the Marianas through Thursday, to then become moderate along north
and east facing reefs as an easterly swell generated by distant
Typhoon Dolphin (12W) arrives. Surf will continue to increase along
all reefs for much of the week as the easterly swell and newly
developing westerly swells increase, with a chance for hazardous surf
to form by the end of the week.
&&
.Tropical Systems…
Typhoon Dolphin has strengthened significantly since yesterday, with
current winds of 140 mph, adding 70 mph to it’s maximum winds since
yesterday’s Tropical Weather Discussion. Dolphin is centered near
14.3N 168.7E, moving west-northwest at 10 mph. Dolphin is expected
to weaken slightly over the next 12 hours due to entering a region of
slightly stronger vertical wind shear between 500 and 300 mb.
Satellite trends do show that Dolphin has halted it’s intense
strengthening, with cooling temps in the eye and slight warming in
the eyewall. These conditions are also indicative of an eyewall
replacement cycle, which would also account for little change to
slight weakening as it goes through this cycle. A 28/1418Z AMSR2 pass
also helps support this scenario, showing a tiny inner core with a
more intense outer spiral band. Overall, Dolphin looks to begin to
intensify again late tonight, possibly becoming a Super Typhoon
Thursday night or Friday. Dolphin is expected to make a slight turn
toward the northwest over the next 12 to 24 hours, with little change
in speed. Dolphin looks to pass south of Wake Island some time
Thursday, and if strengthening resumes, could bring damaging wind and
seas along with torrential rain to Wake Island. Residents of Wake
Island should continue to monitor the progress of Typhoon Dolphin
closely.
For more information on TY Dolphin, please refer to bulletins issued
by the Joint Typhoon Warning Center (JTWC) under WMO header WTPN31
PGTW and by the National Weather Service under WMO header WTPQ31
PGUM.
A weak circulation, JTWC’s Invest 94W, is centered near 12.4N
140.5E. Invest 94W is currently rated sub-low, meaning little or no
development is expected over the next few days. 94W is not expected
to strengthen much, if at all, as it continues to move slowly W over
the next few days. 94W is not expected to directly impact Palau or
Yap State, however, it could enhance monsoon flow, resulting in a
monsoon surge over the next day or two. Invest 94W will be monitored
closely over the coming days for any changes to these expectations.
&&
.Eastern Micronesia…
The monsoon trough continues to produce bands of convection across
portions of eastern Micronesia. Unfortunately, it’s becoming more
difficult to identify exactly where the flare ups will occur.
Therefore, an overall unsettled forecast continues, with POPs
(Probability of Precipitation) remaining in the 30 to 50 percent
range with the trough. Majuro is currently in a dry slot, however,
this is not expected to remain the case through the night.
Therefore, decided to bring scattered showers into Majuro later this
evening. For Kosrae, the island is found along the far southeast
edge of the convection, but this is also expected to increase through
the evening. Overall, not much of a change as the monsoon trough
will be pulled a bit farther north as TY Dolphin progresses, allowing
a drier pattern to move into Pohnpei and Kosrae for the weekend. The
monsoon trough will eventually break away from Dolphin and
reestablish a bit farther south, but looks to continue to influence
the Marshalls into next week.
For the marine forecast, combined seas will gradually build over the
next couple of days due to strengthening TY Dolphin. Currently, seas
look to remain below the 10 foot threshold for a Small Craft
Advisory, however, this could change depending on strength and
movement of Dolphin. Moderate to fresh winds are expected to
continue for the next day or two at Pohnpei and Kosrae before slowly
subsiding, reaching light to gentle for Kosrae by Friday and gentle
to moderate for Pohnpei over the weekend. Gentle to moderate winds at
Majuro will become light to gentle Thursday night into next week.
&&
.Western Micronesia…
An unsettled monsoon pattern spans nearly all of Micronesia. The
western portion of the monsoon trough remains anchored just north of
Palau and Yap, where convergent, moderate to fresh westerlies are
producing scattered to numerous showers and isolated thunderstorms,
mainly just north of the islands. A weak circulation embedded within
the trough, Invest 94W, is helping to focus most of the convergence
and showers just north and northwest of Palau and Yap this afternoon.
Far to the east, widespread cloud cover is seen across much of Chuuk
State, associated with prior deep convection near and to the north
of Weno. Model guidance maintains this broad, convergent monsoon
pattern near the islands over the next few days, but a gradual
northward shift is expected through the weekend, starting with the
eastern extent of the monsoon trough as Typhoon Dolphin lifts to the
northwest. This will enable a slightly drier, but breezier pattern
to begin setting up across the region starting with Chuuk, then
spreading westward.
Benign marine conditions continue, but seas will 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 a long-period swell arrives from the northeast,
emanating from TY Dolphin. This could bring challenging conditions to
small craft in Chuuk State through the weekend, as well as
increasing surf along west, north, and east-facing reefs, which could
potentially become hazardous. The magnitude and exact timing of
these impacts remains uncertain, and will depend in part on the later
track and development of Dolphin far to the northeast. In the
meantime, altimetry and Yap buoy data show combined seas between 3
and 5 feet across the region.
&&
.GUM WATCHES/WARNINGS/ADVISORIES…
GU…None.
MP…None.
Marianas Waters…None.
&&
$$
Marianas: Montvila
East Micronesia/Tropical Systems: Kleeschulte
West Micronesia: DeCou
Alert Expiration: 2026-07-29T16:15:00+00:00
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