Area Forecast Discussion
Issued by NWS Tiyan, Guam

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FXPQ50 PGUM 140817

Area Forecast Discussion
National Weather Service Tiyan GU
617 PM ChST Mon Oct 14 2019

.Marianas Synopsis...
Convergent east to southeast flow prevails across the Marianas.
Recent radar indicates isolated showers and thunderstorms, with
most shower activity near Tinian and Saipan. Water vapor imagery
reveals a weak upper-level trough draped NW to SE just east of the
Marianas. Seas are around 5 to 7 feet with most energy


Pushed back scattered showers until midnight tonight based on recent
satellite, radar, and airport observations. Although the last visible
images upstream of the Marianas are rather unimpressive in terms of
showers, still expect the convergent easterly flow and upper-level
trough to squeeze out scattered showers during the wee hours tonight.
Ample moisture and light winds should continue to support isolated
thunderstorms through Tuesday afternoon, particularly for the western
waters such as west of Orote Point. A dry pattern is still forecast
for Wednesday through Friday as dry air in the mid-levels limits
shower activity. That said, if balloon soundings reveal slightly more
moisture than current guidance suggests, isolated thunderstorms may
develop in the western coastal waters near the islands.

A disturbance is still expected to approach from the east early next
week with an increase in showers possible. The "seed" for this
disturbance appears to be east of the dateline at this time so held
off on any changes to the long-term forecast.


Extended the high surf advisory through Tuesday afternoon based on
several factors...observers from Guam and Saipan estimated surf up
to 10 feet today around noontime today and Ritidian/Tanapag buoys
measured another surge in NNW swell this afternoon. Lingering north
swell from Typhoon Hagibis can be expected through Wednesday night.


.Eastern Micronesia and Chuuk...
This afternoon a surface trough stretched across the eastern half of
Micronesia with a circulation on the trough near 12N170E. Low-level
convergence south of the trough brought scattered showers and
isolated thunderstorms to Pohnpei today and will continue through
the night. The same area of convergence will push across Kosrae and
produce scattered showers and isolated thunderstorms there tonight.
The circulation will move southwest then west, passing north of
Pohnpei by Tuesday night. This will generate isolated showers and
thunderstorms across Pohnpei and Kosrae through Wednesday night.
High pressure will build across Pohnpei and Kosrae in the wake of the
circulation and keep showers to a minimum Thursday through Saturday
at Pohnpei and on Thursday at Kosrae.

As the circulation continues westward it will bring isolated showers
and thunderstorms to Chuuk Tuesday through Wednesday night.

High pressure already covers the Marshall Islands and only isolated
showers are expected there tonight through Wednesday. A surface
trough will push across the Date Line Tuesday night. It will move
westward and bring scattered showers and isolated thunderstorms to
Majuro Wednesday night and Thursday and to Kosrae Friday and


.Palau and Yap...
A surface trough stretched across the western half of Micronesia along
10N with a circulation on the trough located near Yap. Afternoon
satellite imagery depicted isolated showers and thunderstorms south
of trough and circulation over Yap and Palau, and this activity
should continue through much of the night. The trough and circulation
is predicted to break up and weak high pressure will build across
Palau and Yap. Expect only isolated showers Tuesday through Saturday
at Palau and Yap.

Residual north swell will continue to produce hazardous surf of
7 to 9 feet on north facing reefs tonight and Tuesday. Wave watch
model data predicts the swell should fall below hazardous levels
by late Tuesday afternoon.


GU...High Surf Advisory until 6 PM CHST Tuesday for GUZ001>004.

Marianas Waters...None.


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