861
FXPQ50 PGUM 070747
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
547 PM ChST Mon Sep 7 2026

.Marianas Synopsis...
Satellite and radar imagery depicts partly cloudy skies and scattered
showers over Guam`s southern coastal waters and isolated showers
elsewhere. Altimetry indicates combined seas of 3 to 4 ft with a
couple of readings peaking at 5 ft.

&&

.Discussion...
With the leading edge of the col now to the northwest of the islands,
an area of slightly drier air and light to gentle northerlies has
moved in over the region. This pattern is conducive for island-effect
showers as air over the cooler ocean crosses the warmer islands from
north to south, ending up as an unstable air mass by the time it
reaches Guam. Wind speeds should gradually increase from Saipan to
Guam, resulting in a trail of scattered showers and isolated
thunderstorms over southern Guam and adjacent coastal waters. This
pattern is forecasted for Tuesday afternoon should the skies remain
clear enough, followed by a slightly wetter period and isolated
thunderstorms beginning Tuesday night through midweek, with winds
shifting out of the northeast as a potential circulation approaches
the Marianas. In the latter half of the week, a dry easterly trade
pattern may return to the region, with isolated light showers (10%
chance of showers) a possibility during the weekend.

&&

.Marine...
Combined seas of 3 to 4 ft are forecasted to continue through much of
the work week before an easterly trade swell mixes with the
predominant westerly swell around midweek. Combined seas may increase
a foot or two, possibly peaking at 4 to 6 ft during the weekend. In
addition, long-period pulses of the easterly and westerly swells from
distant tropical cyclones in the western and central Pacific may
reach the coastal waters near the end of the week. At this time,
surf heights and rip current risks are not expected to become
hazardous. This will continue to be monitored should conditions
change.

&&

.Eastern Micronesia...
The monsoon surge is seen to the south of Kosrae this evening and
is still expected to move into Kosrae and Pohnpei over the next day
or two. As for Majuro, a band of strong convergence south of the
monsoon trough brought scattered showers and the risk of
thunderstorms to the atoll this morning. This looks to be the
beginning of a more unsettled pattern across eastern Micronesia.
Latest model guidance does show a few inches of rainfall across the
region over the next 5 days, but nothing that would cause any
flooding on Kosrae or Pohnpei. Overall, it looks like the region
will maintain a good water supply through at least the next week or
two.

As for the marine forecast, there is a major change to both Pohnpei
and Kosrae. For Majuro, no major changes from the previous forecast,
with winds and seas remaining fairly benign. However, it now looks
like the monsoon surge developing over Kosrae and Pohnpei will be a
bit stronger than previously expected, with winds possibly reaching
Small Craft Advisory (SCA) levels for a day or two, so a SCA may
need to be issued Tuesday afternoon. Otherwise, the forecast remains
the same.

&&

.Western Micronesia...
A ridge of high pressure persists over Yap and Palau, leading to
quiet conditions over the next few days. During this period of drier
weather, haze sourced from distant wildfires in Indonesia are
expected to continue. Island-effect convection produced a stray
thunderstorm over northeastern Babeldaob earlier this afternoon.
Similar conditions are expected Tuesday, so have included afternoon
island-effect showers and a slight chance of thunderstorms for
eastern Babeldaob. The disturbance that was between Pohnpei and Chuuk
yesterday, remains largely disorganized with 850mb vorticity keying
in on a vorticity lobe southwest of Chuuk Lagoon. A broad area of
showers and a few thunderstorms are spread out across southwestern
Chuuk State and eastern Yap State along northwesterly and west-
southwesterly convergence around the monsoon trough and embedded
disturbance. Over Chuuk Lagoon, patchy, isolated to scattered showers
are expected over the next few days. Model guidance shows the nearby
lobe of vorticity shifting northward and blending into the monsoon
trough. Southwesterly convergence begins to set up across Chuuk
Lagoon, bringing another increase in scattered showers and isolated
thunderstorms towards the latter half of the week. Overall, Yap and
Palau remain on the outskirts of this developing pattern, but
depending on the proximity of the monsoon trough, low-end scattered
showers may return to Yap Wednesday night through Friday. Palau may
see a bit more cloud cover and moderate showers, but overall coverage
is expected to be more isolated.

Latest altimetry data shows combined seas remain steady at 2 to 4
feet near Palau and Yap, with a slight decrease to 3 to 4 feet at
Chuuk. Benign marine conditions are expected to continue over the
next several days, with seas increasing to 4 to 6 feet around
Thursday for Chuuk coastal waters due to an increase in south to
southeast swell. Light to gentle winds persist over the next several
days with an increase in gentle to moderate southwesterly winds at
Chuuk on Wednesday, increasing to gentle to fresh late week. Yap and
Palau may see a slight increase to light to moderate northwesterlies
towards the weekend.

&&

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

$$

Marianas: Mesa
East Micronesia: Kleeschulte
West Micronesia: Cruz