796
FXPQ50 PGUM 110822
AFDGUM

Area Forecast Discussion
National Weather Service Tiyan GU
622 PM ChST Tue Mar 11 2025

.Marianas Synopsis...
A dry trade wind pattern persists across Guam and Rota with isolated
showers and partly cloudy skies seen across the area. To the north,
cloud cover and showers are more prevalent, due to the proximity of a
shear line stalled over the northern CNMI just north of Saipan
coastal waters. Data from nearby stationary buoys and SOFAR drifting
buoys indicate 6 to 8 foot seas near Guam and Rota, and 7 to 9 foot
seas around Tinian, Saipan, and the northern CNMI.

&&

.Discussion...
Satellite and model trends point to an increase in showers overnight
for Tinian and Saipan along the southern periphery of the shear
line, the leading edge of which is stalled near Anatahan. Afternoon
scatterometry shows fresh to strong trade winds north of the shear
line, with moderate to fresh trades south of this boundary over the
Marianas. The shear line will begin to lift northwest and away from
the islands by Thursday night, but in the meantime, expect higher
shower chances, cloud cover, and wind gusts near Tinian and Saipan
over the next day or so. Showers look to remain isolated for Guam
and Rota through the forecast period, with slight increases possible
from time to time due to weak, transient areas of trade-wind
convergence or subtle trade-wind troughs crossing the region. The
main forecast concerns are the potential for hazardous surf and seas,
particularly for the latter half of the week.

&&

.Marine/Surf...
Moderate to fresh trades are expected for Tinian and Saipan tonight
with a shear line stalling just to the north. A significant
northerly swell has allowed for seas to increase to near-hazardous
levels of 7 to 9 feet for Tinian and Saipan and 6 to 8 feet for Guam
and Rota. These seas will likely increase another 1 to 2 feet come
Thursday night with the arrival of another long-period north swell,
which would bring them to hazardous levels for small craft. The
increase in north swell tonight will also produce hazardous surf for
north facing reefs come Wednesday morning, along with a high risk of
rip currents for north and east facing reefs. The next pulse of
north swell arriving Thursday will likely maintain these surf
hazards, potentially through the end of the week.

&&

.Eastern Micronesia...
Moderate to fresh trades persist across the region with just a few
passing trade-wind showers seen across Pohnpei and Kosrae States.
Meanwhile, showers and thunderstorms are seen just south of Majuro,
perhaps a combination of developing trade convergence along the ITCZ
with some assistance from an upper-level trough that is perched atop
the Marshalls. This convection is expected to spread northward
overnight, bringing increasing showers to the central Marshalls along
with gusty conditions. The next couple of days will see a slight
wetting trend as showers begin to increase between 4N and 8N as the
ITCZ gradually becomes better organized. By late week, models depict
a fairly solid band of convection along the ITCZ with model guidance
suggesting anywhere between 2 and 5 inches of rain fall through
Saturday for areas under the coverage of ITCZ convection.

The main weather concern will be the marine situation. Have allowed
the Majuro SCA to expire as satellite altimetry shows seas have
fallen below 10 ft. At Kosrae, the high surf advy continues until
Thursday, though recent model guidance suggests swell and surf could
fall enough Wednesday to fall below hazardous levels.

As noted in recent discussions, a large north swell will quickly make
its way into the area beginning Thursday night. These waves will be
coming from a strong north-Pacific cyclone currently about 2200mi
north of Pohnpei. This system is continuing eastward into the central
north Pacific packing winds near hurricane/typhoon force. Wave model
guidance shows 8-11 foot north swell with periods of 14-17 sec around
the peak of this event Friday - also well timed with the full moon
phase and its higher high tides. All this supports the development
of hazardous surf and marine conditions for small craft. Additionally
for islands and atolls well exposed to the north, there will be the
increased threat for significant erosion and some minor inundation.
Today`s PacIOOS wave run-up guidance for Majuro still shows the
potential for minor inundation around high tides. While more southern
atolls could see some shadowing from atolls farther north, the
northernmost atolls will see the largest and unimpeded swells.

&&

.Western Micronesia...
Chuuk is currently between shower areas, one to the north and one to
the south, so showers are isolated. Scattered showers will move in
soon on Wednesday though, and could become numerous Friday night
through Sunday, then remain scattered through Tuesday. Overall,
fairly good potential for a rather wet week at Chuuk coming up.

In the Chuuk Waters, gentle to moderate trades tonight will build to
moderate to fresh by Thursday, and remain so through Saturday, then
return to gentle to moderate levels Sunday. Seas of 5 to 7 feet will
build to between 7 and 9 feet by Thursday night which will continue
through Saturday, then begin to diminish Sunday. While these
conditions are below levels hazardous for small craft, they will
still be challenging for mariners.

Yap is fairly dry at the moment, by Wednesday night however, showers
could lift to the north and their northern edge could involve Yap
island. These scattered showers could continue through Friday night.
After a brief break on Saturday and Saturday night, more showers
could be in store Sunday through Tuesday. If this comes to fruition,
it could help ease the drought, so let`s hope it happens.

Yap Waters will have moderate to fresh winds with occasional strong
gusts through Thursday night. Afterwards, winds will be gentle to
moderate, although strong gusts could continue into Friday. Since the
gusts should just be occasional, they are not expected to be
hazardous to small craft. They will make marine conditions
challenging though, as will seas building from 6 to 8 feet to between
7 and 9 feet.

While Koror, Palau had some pretty good shower activity today thanks
to a mesoscale convergence zone that set up, showers should be
isolated tonight through Wednesday night. A period of scattered
showers will follow as showers to the southeast move westward and
build northward, lasting from Thursday through Saturday. A brief
period of drier weather will commence Saturday night and Sunday, then
back to scattered showers Sunday night through Tuesday.

Koror, Palau Waters will have gentle to moderate winds through
Saturday, with occasional strong gusts through Thursday night. This
will make marine conditions challenging through Thursday night. Seas
will be 6 to 8 feet through Saturday, then diminishing on Sunday,
possibly as low as 4 to 6 feet.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...High Rip Current Risk from Wednesday morning through late Thursday
     night for GUZ001.

     High Surf Advisory from 6 AM Wednesday to 6 AM ChST Friday for
     GUZ001.

MP...High Rip Current Risk from Wednesday morning through late Thursday
     night for MPZ001>003.

     High Surf Advisory from 6 AM Wednesday to 6 AM ChST Friday for
     MPZ001>003.

Marianas Waters...None.
&&

$$

Marianas: DeCou
East Micronesia: Aydlett
West Micronesia: Stanko