Area Forecast Discussion
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FXPQ60 PGUM 250212

Area Forecast Discussion
National Weather Service Tiyan GU
1205 PM ChST Mon Sep 25 2017

Satellite and radar imagery show showers and thunderstorms developing
to the southeast and east. A weak surface trough, with some influence
of an upper-level low to the east, is triggering this activity.
Showers will increase over Guam and Guam waters early this afternoon
and then spread northward as the line pushes through the area. Radar
velocity data show the presence of gusty winds with some heavier
showers, so some gusts up to 25 kt or so are not out of the question
out on the water. Showers are expected to decrease around sunset.


.Prev discussion... /issued 703 AM CHST Mon Sep 25 2017/

Marianas Synopsis...
Scattered clouds and isolated showers prevailed mainly east of the
Marianas early this morning. Combined seas are generally 3 to 5 feet
at the buoys.

A surface ridge is west of the Marianas with weak troughing moving in
by Tuesday, the trough amplifies a bit and gets some upper support.
The trough remains over the region and another upper low moves over
the area on Wednesday. During this time, there will likely be at
least some times of scattered showers, but it is difficult to
pinpoint. Then by later in the week, should be less moisture so
should be a return to isolated showers and thunderstorms. For now,
did not make any major changes to the forecast.

Buoys remain in the 3 to 5 foot range and will likely drop about a
foot over the next day or so. However, latest guidance indicates
surf will decrease on Tuesday, but we could be on the cusp of low
or moderate depending on how quickly the decrease occurs.

Eastern Micronesia...
A trade-wind trough from east of the date line has migrated into
southern portions of the Marshall Islands, Kosrae state and
Pohnpei state. This will bring unsettled weather to Majuro today
and Kosrae tonight. Pohnpei will see a slight increase in clouds
and showers starting tonight, however the bulk of the action will
be to their south. Another trough will bring a second round of
unsettled weather about Thursday. Winds and seas are expected to
remain benign, however.

Western Micronesia...
A trade-wind trough currently departing Chuuk will begin to
affect Yap this afternoon, and could last through Tuesday. With
the trough departing, Chuuk will have fair weather until Tuesday
when the trough near Pohnpei begins to build in. On Thursday, the
next trough will give it a reinforcing shot making for unsettled
weather Thursday and Friday at Chuuk. Meanwhile a weak circulation
is spraying showers and thunderstorms all over in the area near
Koror and just west of Yap. This will continue through Tuesday,
then the weather at Yap will stabilize while at Koror the showers
will become scattered. Then, by Thursday, both Yap and Koror will
be starting to dry out. As in Eastern Micronesia, seas and winds
are forecast to remain benign.


Marianas Waters...None.


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