538
FXPQ50 PGUM 010744
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
544 PM ChST Tue Jul 1 2025

.Marianas Synopsis...
Satellite imagery and radar show isolated showers for Guam and Rota
and scattered showers for Tinian and Saipan. Altimetry shows combined
seas of 3 to 5 feet, while Ipan and Ritidian buoys show heights of 3
to 4 feet.

&&

.Discussion...
Scattered showers are seen just outside the Marianas waters. These
showers are anticipated to build in overnight for much of CNMI, Guam
is expected to remain in a clearer region. A break in the monsoon
trough will give way to a drier next few days. Showers are
anticipated to pick back up around the end of the workweek. Over the
weekend, showers are anticipated to be minimal.

&&

.Marine...
Benign sea conditions are anticipated throughout the forecast
period. Winds are expected to be light to gentle. Surf is the highest
along east facing reefs. An incoming southwesterly swell is
anticipated to arrive over the weekend. This may increase surf and
rip current risk along south and west facing reefs. The risk of rip
currents remains moderate along east facing reefs.

&&

.Tropical systems...
JTWC`s (Joint Typhoon Warning Center) Invest 90W, currently showing
a defined circulation center, but is roughly located well north-
northeast of Saipan near 22.5N 148.2E, moving northward. Numerous
showers and isolated thunderstorms are found to the east of the
invest. 90W is now rated low, meaning it is expected to develop, but
not expected to become a significant tropical cyclone within the next
24 hours. Although a closed circulation is not seen now, 90W is
becoming more organized, with a TUTT cell near 21N145E providing
divergent flow in the upper levels. Models do favor 90W developing
into a more organized circulation as it continues north. For more
information on Invest 90W, see bulletins issued by JTWC under WMO
header ABPW10 PGTW.

&&

.Eastern Micronesia...
For now, the Inter-Tropical Convergence Zone (ITCZ) has weakened a
bit, with less convection seen along the boundary. There is a flare
up of convection with a trade-wind trough that is moving toward
Kosrae. This trough looks to bring increased convection to Kosrae
later this evening. Another weak trough is seen approaching Pohnpei
and is expected to bring low-end scattered showers and possible
thunderstorms to Pohnpei by midnight. Otherwise, the ITCZ is expected
to strengthen a bit, with increasing showers spreading across the
region. An overall unsettled pattern looks likely for the region as
the ITCZ strengthens and weak trade-wind troughs move through. There
will be brief periods of isolated showers through the week due to the
wavering of the ITCZ and in between troughs moving through.

No changes were made to the marine forecast. Combined seas of 5 to 7
feet at Majuro slowly subsiding over the next few days, dropping to
between 3 and 5 feet for the weekend. Seas of 4 to 6 feet for Kosrae
and Pohnpei could reach 5 to 7 feet tonight into Wednesday before
subsiding to between 3 and 4 feet for the weekend. Gentle to moderate
winds are expected through the week for Kosrae and Majuro, with
gentle to moderate winds becoming light to gentle for Pohnpei
Wednesday night.

&&

.Western Micronesia...
The wet, southwesterly monsoon pattern looks to continue for tonight
with rounds of heavier showers and thunderstorms for both Yap and
Palau. Could see fresh to potentially strong gusts with the bursts of
showers. A surface ridge will try to creep west and may push the
edge of the monsoon flow to the north and west of Palau and Yap, with
generally isolated to low-end scattered showers expected through the
end of the week. Through the weekend into early next week, may see
the ridge break down over the region and a slow return to a wetter,
monsoon-like pattern.

Outside of gusty winds and choppy seas near heavier showers and
thunderstorms, fairly benign marine conditions expected, with seas 3
to 5 feet and gentle to at times moderate winds will diminish
slightly over the coming days as the monsoon swell and winds
decrease. By late weekend into early next week, a longer-period
northwest swell generated by a possible distant tropical cyclone
developing northeast of the Philippines could build into the region,
increasing seas ans surf.

For Chuuk, a surface trough lifting northwest along the leading edge
of a building ITCZ will bring increasing showers over the coming
days. Expect isolated showers this evening to become scattered after
midnight. High-end scattered to numerous showers and isolated
thunderstorms are expected Wednesday through Thursday as the
aforementioned features pass through. While coverage looks to
diminish beyond Thursday as the trough pushes away and the ITCZ
diminishes, are still expecting scattered showers and isolated
thunderstorms into the weekend as subtle surface features pass
through and weak east-southeast flow linger.

Gentle to moderate winds are expected through Thursday. Fresh to
potentially strong gusts are possible near heavier showers and
thunderstorms as well. Winds look become light to gentle by Friday as
the trough pushes west. Seas of 4 to 6 feet will be possible through
Thursday night with the disturbance pushing through, then lowering
around 2 feet by the weekend.

&&

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

&&

$$

Marianas: Bowsher
East Micronesia: Kleeschulte
West Micronesia: Slagle