Area Forecast Discussion
Issued by NWS Tiyan, Guam

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FXPQ50 PGUM 132046

Area Forecast Discussion
National Weather Service Tiyan GU
646 AM ChST Mon Oct 14 2019

.Marianas Synopsis...
A broad, but disorganized surface trough extends from north of Palau
to the south of the Marianas with a couple weak circulations found
along the trough. Isolated showers and thunderstorms are found across
the Marianas while scattered showers are found well to the west and
farther southeast near 10N150E. Buoys show seas between 5 and 6 feet
across the area.


The broad disturbance sitting just south of the Marianas will
maintain a weakly convergent flow over the area through Tuesday night
that will keep isolated thunderstorms nearby into midweek. Isolated
showers today will also increase to scattered tonight as an upper-
level trough to the northeast drops over the Marianas this evening.
Drier weather is expected for the latter half of week. A disturbance
will approach from the east over the weekend and early next week that
will bring increasing clouds to the region along with a slight chance
of thunderstorms. Only in the most recent model runs have models
shown an increase in precipitation for early to the middle of next
week. Should subsequent model runs maintain the trend, the long-
range forecast will likely be changed accordingly.


Buoys continue to show a steady decrease in the northwest to north
swell with the occasional surges. These surges bring surf back above
the 9 ft threshold for hazardous surf, thus have left the high surf
advisory in effect for the day. By this evening, surf should fall
below hazardous levels and stay below 9 ft as swell continue to
subside. Combined seas will fall to between 4 and 5 feet by midweek.


.Eastern Micronesia and Chuuk...
A surface trough north of eastern Micronesia and an embedded
circulation near 12N170E is digging southward this morning. Weak
ridging kept fair weather in place overnight at Majuro and Kosrae,
but showers and thunderstorms are creeping southward. IR satellite
shows showers and thunderstorms over Pohnpei and tapering over Chuuk
along the eastern end of the monsoon trough to the west. This trough
will shift slowly west-southwest keeping a relatively wet pattern in
place a couple days at Kosrae and Pohnpei, and Chuuk around midweek.
A surface trough will cross the Date Line around Wednesday and will
bring more showers to Majuro on Thursday and Kosrae on Friday.


.Western Micronesia for Yap and Palau...
A broad and weak circulation remains near Yap within the weak monsoon
trough stretching along 10N eastward to near Chuuk. Only patchy
showers and clouds and a few thunderstorms are seen at Yap and Koror
this morning. The trough and circulation will lift to the west-
northwest with winds becoming light and variable over the region with
drier weather. Dry weather will persist through the end of the week
with winds shifting to the east by Thursday.

The High Surf Advisory for Yap and Koror remain in effect for
hazardous surf of 8 to 10 feet along north facing reefs. Large,
long-period north swell continues to subside and should fall enough
to allow surf to fall below hazardous levels by Tuesday morning.


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

Marianas Waters...None.


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