Area Forecast Discussion
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FXPQ60 PGUM 080749 AAA
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Area Forecast Discussion...Updated
National Weather Service Tiyan GU
550 PM ChST Thu Dec 8 2016

Updated to add Micronesia Discussions

.Synopsis...
Satellite and Radar show patchy clouds and isolated showers moving
across Guam and southern Guam Coastal Waters. Skies are fair over
Saipan, Tinian and Rota, and just east of Guam. VAD gradient winds
are from east-northeast at 15 to 20 kt. Local Buoys show combined
seas ranging from 5 to 8 feet.

&&

.Discussion...
Re-combined forecast zones. The trade-wind disturbance is exiting
the local area, and the clouds and few showers over southern Guam
Coastal Waters will be moving west of the forecast zones this
evening. Partly cloudy skies and isolated showers are expected to
prevail in the coming days. There is still an area of disturbed
weather far south of Guam, but Satellite trends farther upstream
indicate relatively dry trades can be expected for the Marianas
through the longer term. GFS model shows some deeper atmospheric
moisture over the Marianas on Saturday and early next week, but
only isolated showers are expected at this time.

&&

.Marine...
Models show moderate trade winds the next several days at least.
Combined seas of 5 to 8 feet tonight will subside to 4 to 7 feet
Friday through the weekend. The risk of rip currents will remain
moderate through the weekend also, especially along the eastern
shores.

&&

.Eastern Micronesia.
A series of weak trade-wind disturbances are going to maintain
widely scattered showers and a thunderstorm or two near Pohnpei
until Friday evening, and Chuuk thru Saturday. Then a period of
dry trade-wind weather is expected for Pohnpei thru Saturday, and
Chuuk until late Sunday night. Farther east, a weak circulation is
centered southeast of Kosrae near 1N165E and a surface trough is
approaching the Marshall Islands from 176E. Very dry air above
800mb as illustrated by the latest sounding plot from Majuro,
should maintain fair conditions near Kosrae until late Friday
night, and Majuro thru Friday afternoon. As this trough continues
to push westward, it will merge with the circulation southeast of
Kosrae on Friday night. Therefore anticipate showers associated
with this combined system to affect Majuro by Friday evening, and
Kosrae near early Saturday morning. This same wet regime might
also reach Pohnpei on Saturday night and possibly Chuuk early next
week. After the passage of this system, drier northeasterly trades
should bring back partly cloudy skies for the entire region from
east to west next week.

&&

.Western Micronesia...
Reasoning for the Chuuk forecast is included under the Eastern
Micronesia section above.

A weak near-equatorial trough and related low-level circulation
persist near Koror at 8N but south of Yap near 4N144E
respectively. Gentle winds near the trough axis should trigger
mainly isolated showers near Koror thru Friday evening. Being
north of the trough and circulation, fair conditions are expected
for Yap until Friday morning. The first trade-wind disturbance of
a series is passing south of Guam this evening. It will approach
Yap on Friday and then Koror on Saturday. As it merges into the
circulation and near-equatorial trough, increasing low-level
convergence will generate sporadic convection across both
locations. The other disturbances upstream will repeat a similar
process and prolong unstable weather for the area into next week.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...None.
Marianas Waters...None.

&&

$$

Simpson/Chan



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