Area Forecast Discussion
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FXPQ60 PGUM 240158 AAA

Area Forecast Discussion...Updated
National Weather Service Tiyan GU
1154 AM ChST Sun Sep 24 2017

A surface trough continues to exit out of the area to the west,
however, convergent southeast winds will still generate showers
and thunderstorms in the area. Satellite and radar imagery show
the bulk of developing showers will pass through Guam and Rota
waters. Prior forecast of diminishing showers at Tinian and Saipan
still looks good with most of the deep convection having moved off
to the west and northwest. The evening forecast package may need
to take note of further developing convection to the southeast
that could sustain scattered showers well into the overnight
hours. A surface ridge to the east is still expected to reach the
area around Monday, bringing a short respite in showers before
another trough reaches the area around Tuesday.


.Prev discussion... /issued 715 AM CHST Sun Sep 24 2017/

Marianas Synopsis...
Latest radar imagery showed showers and thunderstorms around the
Marianas, with an area approaching from the east early this
morning. Otherwise, expect east wind and combined seas generally 4
to 6 feet.

A surface trough was extending across the Marianas. Latest
satellite imagery showed an abundance of clouds to the south and
west, and another area of showers that have just developed near
Guam and near Saipan and Tinian. Additional enhancement is
developing further east. Therefore, have opted to go with
scattered showers this morning, before a return to isolated this
afternoon. The guidance is in good a agreement that a surface
ridge will move over the area later this morning/early this
afternoon and that should hopefully help end any rain chances.

Another trough will follow for Monday night, so isolated thunder
has been left in the forecast. This trough may linger into

As we approach the midweek period, the GFS still wants to develop
a circulation nearby, and most of the other models are not as
robust, if they have anything at all. So, for now did not make
any changes to this portion of the forecast, and will hope for
better model agreement.

Guidance shows an east swell that will remain in the 3 to 5 foot
range through midweek before subsiding.

Eastern Micronesia...
Pohnpei, Kosrae and Majuro are all fairly quiet this morning. A
surface trough now moving across the date line will soon be
changing that. Showers will be increasing at Majuro by Monday. For
now kept the showers isolated at Kosrae and Pohnpei until we can
see more of the evolution of this feature. A period of scattered
showers is possible at either or both of them. It is likely enough
at Majuro that it has been entered into the forecast. With winds
expected to stay below 15 knots and seas below 5 feet, no weather
related hazards are anticipated for Eastern Micronesia this week.

Western Micronesia...
Put in isolated thunderstorms for today at Chuuk as they had some
early this morning. They were probably related to the upper-level
trough. After a couple of quieter days, the trough currently near
the date line could start to affect Chuuk around Tuesday.
According to ASCAT, the highest winds are found near Yap and Palau
around a weak but developing circulation. The day shift issued a
small craft advisory for Yap; retained this although nothing
showed up in the observations. The deep convection is now all west
of the circulation center, indicating some easterly shear. This
should inhibit too much development until the circulation is clear
of Micronesia. Other than the small craft advisory today at Yap,
no weather related hazards are forecast this week in Western


Marianas Waters...None.


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