144
FXPQ50 PGUM 071804
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
404 AM ChST Sun Jun 8 2025

.Marianas Update...
There were no significant changes made to the forecast over night.
The Tropical Upper-Tropospheric Trough (TUTT) remains firmly over the
Marianas. The surface level features, surface-level troughs and
convergence, is expected to dissipate over the next 24 hours. This
will cause the showers to diminish, first over Saipan and Tinian
during the day, and Rota and Guam by night. Isolated showers are
expected to return around Monday. However, with the TUTT remaining
in the area, it won`t take much to bring scattered showers back into
the forecast. Altimetry shows combined seas are 3 to 4 feet, and
both Ipan and Ritidian buoys confirm these heights. The risk of rip
currents remains moderate along east facing reefs and low on all
other reefs.

&&

.Fire weather...
0.18 inches of rain fell yesterday at the Guam International
Airport, which allowed the KBDI to drop to 404, allowing the fire
danger to remain in moderate category. As such, critical fire
weather conditions are not likely to return at this time as we
transition toward a wetter seasonal pattern.

&&

.Tropical systems Update...
Invest 93W has been closed by the Joint Typhoon Warning Center. No
circulation center is now evident and it remains a disorganized
"mess" of convection.

&&

.Eastern Micronesia Update...
A quiet pattern continues with no significant updates needed. The
current MIMIC water vapor imagery shows PWATs (Precipitable Water
Values) holding near 2 inches. However, no surface troughs are in
the area to help focus convergence and any subsequent increase in
shower coverage during the next 18 hours. However, a "surge" of
moisture is crossing the Date Line, with PWATs increasing to near 2.5
inches, accompanied by a modest surface trough. This may allow
scattered showers to develop at majuro Monday.

&&

.Western Micronesia Update...
Palau and Yap:
No significant changes were made as 93W remains poorly-organized. The
southwesterly monsoon remains in the area but is drifting west.
Still, given it`s proximity, rainfall potential at 50 percent
probabilities remains in the forecast for today and tonight.

Chuuk:
We "scaled back" rainfall coverage to isolated showers for today and
tonight (20 percent probabilities). A "ripple" (weak disturbance) in
the flow may allow shower potential to increase slightly for Monday.

&&

.Prev discussion... /issued 513 PM ChST Sat Jun 7 2025/

Marianas Synopsis...
Mostly cloudy skies with scattered showers and gentle to moderate
trade winds prevail across the Marianas this afternoon. Global
Lightning Detection shows that there were a couple thunderstorms
north of Guam. A trade-wind trough is evident on satellite to the
east of the Marianas. Buoys show seas between 3 and 4 feet.

Discussion...
The TUTT remains parked to the west of the Marianas, with a TUTT
cell found north of the northern CNMI. The divergence associated with
the TUTT continues to enhance convection across the region, with
scattered showers and a couple thunderstorms seen across the Marianas
through the day. Showers will remain low-end scattered through the
night. By morning, another trough will approach the Marianas,
interacting with the upper divergence, resulting in POPs (Probability
of Precipitation) increasing into the 40 percent range. Due to the
instability associated with the divergence, thunderstorms remain a
possibility as well. Convection will decrease to isolated showers for
Tinian and Saipan Sunday and for Guam and Rota Sunday night. A dry
trade-wind pattern is then expected to dominate for the rest of next
week.

Marine...
No big changes to the marine forecast. Gentle to moderate trades
will prevail through Sunday night. The trades will then become light
to gentle and remain so through at least the middle of next week.
Combined seas of 3 to 5 feet will subside about a foot Monday. A
southwest to west monsoon swell will move into the area around the
middle of next week.

Tropical systems...
Invest 93W is roughly centered near 14N137E. 93W remains weak and
ill-defined and very disorganized. Latest guidance indicates that
Invest 93W will slowly drift west over the next few days, with
little or no development until it moves west of 130E. Invest 93W
will be monitored closely over the next few days for any changes or
indication of strengthening.

Eastern Micronesia...
A surface trough with a broad buffer circulation to the south and
west of Pohnpei and Kosrae will slowly push west through the
weekend. Convergent flow along the northern and eastern periphery of
the trough could result in low-end scattered showers at times for
Pohnpei through Sunday night. Diffluent flow and drier air have
worked into Kosrae and only spotty showers now expected through the
weekend. A weakening surface trough is passing through Majuro and
looks to bring low-end scattered showers through this evening. Next
week, all three forecast points could see a slight uptick in showers
(probability of precipitation 30 to 40 percent) and a slight chance
of thunderstorms as subtle surface troughs pass through, beginning
Sunday night at Majuro, Monday night at Kosrae, and Wednesday at
Pohnpei.

Light to gentle winds and seas of 2 to 4 feet should prevail through
Monday. Winds and seas look to rise beyond Monday as the trade flow
and a background southerly swell increase.

Western Micronesia...
After the last southwesterly monsoon surge makes its way cross Yap
overnight, an artificial ridge will situate itself over Palau and
Yap. This will bring an unsettled weather pattern with variable
winds, likely to produce patchy showers and some thunderstorms
through Monday. After, gentle to moderate trades will return,
bringing a brief drier cycle until midweek. Chuuk will continue to
see isolated to low-end scattered showers and some thunderstorms
brought by gentle to moderate trades for much of the forecast
period.

Combined seas of 3 to 5 feet are expected at Palau, Yap and Chuuk
for much of next week. Primary southwest swell at Palau and Yap is
expected to weaken enough for the east swell to overtake it by
midweek, adding to already choppy seas.

&&

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

$$

Marianas Update: Bowsher
East/West Micronesia Update: Doll
Marianas: Kleeschulte
East Micronesia: Slagle
West Micronesia: Montvila