483
FXPQ50 PGUM 220737
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
537 PM ChST Thu May 22 2025

.Marianas Synopsis...
Gentle to moderate trades prevail over the Marianas, with satellite
imagery indicating just some clouds moving off the islands and into
the waters. A few ripples of clouds are entering the eastern waters.
The buoys indicate seas are 3 to 4 feet. Altimetry shows combined
seas of 4 to 6 feet.

&&

.Discussion...
A dry trade-wind pattern resides over the Marianas. Partly cloudy
skies are expected through most of the forecast period, with sky
cover potentially increasing to mostly cloudy by the middle of next
week. The main change to the forecast is a slight increase in
Probability of Precipitation (PoPs) to 20 percent to account for
island convection along the western side of the islands.

Time-heights suggest the next injection of moisture will come near
the beginning of next week. This injection is noticeably more moist
and reaching farther down in the atmosphere than the last injection.
Looking upstream on the CIMMS MIMIC, PWATs appear to be higher
upstream. Omega values, one of our lifting matrices, also suggests
showers are more likely. As such, included slightly higher shower
coverage in the forecast beginning on Memorial Day.

&&

.Marine...
Benign seas of 3 to 5 feet are expected the next few days, before
gradually falling through the beginning of next week, due to the
primary swell weakening. North and east facing reefs remain at
moderate risk of rip currents through Saturday. As the primary swell
diminishes, so too will the risk of rip currents. This risk may fall
to low on all reefs by the beginning of next week.

&&

.Fire weather...
No rain has fallen since midnight. The KBDI remains at 744, which is
in the high category due to the sustained winds remaining below the
20 mph threshold. Showers are not expected to produce enough rain for
the remainder of the day, to prevent the KBDI from rising tonight.
Both winds and relative humidity values look to remain below Red Flag
Warning criteria the next few days.

&&

.Eastern Micronesia...
A fairly dry and gentle trade-wind pattern extends across the region,
with a couple of minor troughs in the northern Marshall Islands and
a third trough currently well east of Majuro, generating spotty to
scattered showers. Drier weather will continue at Pohnpei and Kosrae
through at least Friday, but with winds being on the lighter side,
both islands could see some increased cloud cover and spotty showers
during the afternoon hours due to a island heating in the morning
caused by lighter winds and partly cloudy skies. At Majuro, the
trough to the east will approach Majuro later tonight and increase
showers over the atoll. Global models continue to depict a band of
convergence developing near Majuro starting Friday and strengthening
into early next week as it spreads eastward to Pohnpei and Kosrae
late this weekend, increasing showers and the potential for
thunderstorms at all locations. Both the GFS and ECMWF initially
keep most of the showers near or south 8N. However, around the
middle to latter half of next week, the GFS, and the ECMWF to a
lesser extent, show a north-northwest shift that may bring additional
showers to the northern islands of the Marshalls such as Kwajalein
and Wotje. As this is still about 6 to 7 days out, continue to
monitor the forecast to see if this trend continues.

Scatterometer data continues to show a mostly gentle trade-wind
pattern across the region with winds expected to become gentle to
moderate, and at times fresh at Majuro, by Sunday. Combined seas are
currently around 4 to 5 feet across the region and not expected to
change much, especially for Pohnpei and Kosrae through early next
week. Models show the east swell slowly building to the east of
Majuro this weekend, which will cause seas to build to between 4 and
6 feet by early next week, remaining as such for the rest of the
week.

&&

.Western Micronesia...
An unsettled weather pattern will continue to bring patchy showers to
much of western Micronesia. Higher-end showers and thunderstorms will
arrive to Yap Friday night, and to Palau Saturday, lasting as such
through the weekend. Showers will then taper down slowly at both
locations by early next week. Meanwhile at Chuuk, on-and-off showers
brought by moderate trades will continue through tonight, followed by
a drier regime returning through the weekend.

Combined seas of 3 to 5 feet are expected to diminish by a foot
across all three locations by the weekend, staying as such into early
next week.

&&

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

$$

Marianas: Bowsher
East Micronesia: Schank
West Micronesia: Montvila