Area Forecast Discussion
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FXPQ60 PGUM 220804

Area Forecast Discussion
National Weather Service Tiyan GU
410 PM ChST Fri Sep 22 2017

.Marianas Synopsis...Northeast winds and isolated showers and
thunderstorms prevail over the Marianas this afternoon.


Did a rapid update of the forecast not too long after issuing it.
Satellite imagery and radar earlier in the afternoon showed only a
few isolated showers over the local area and had only isolated
showers in the forecast for tonight. By late afternoon a few
thunderstorms had developed over the Marianas. An upper-level low
located near 20N143E is probably the culprit setting off the
thunderstorms over the local area. A few thunderstorms will be
possible through the night.

A surface trough could be found on the afternoon analysis between
Pohnpei and Chuuk. This trough will push west and generate scattered
showers and isolated thunderstorms mainly south of 10N. The trough
will come close enough to produce a few isolated thunderstorm across
the Marianas this weekend. Another surface trough will follow quickly
behind the trough an extend the possibility of isolated thunderstorms
Monday and Monday night.


Observations this afternoon from Ipan, Ritidian and Tanapag buoys
indicate sea heights between 3 to 4 feet. The buoys show the and east
swell and Ritidian and Tanapag show a northeast swell.  Models show
that the east swell will persist through the forecast and the
northeast swell is predicted to remain until Monday. Neither swell
will get very large and the rip current risk should remain low.


.Eastern Micronesia...
This discussion includes Chuuk state.
Active convection prevails in this region as the large surface
trough extends from southwest of Chuuk eastward to the Marshall
Islands. Scattered showers and isolated thunderstorms is expected
through the weekend for Chuuk and Pohnpei as this trough
progresses westward. Improved weather in store for Majuro over the
weekend. However, weak trade- wind convergence will bring back
isolated thunderstorms for most locations by early next week.


.Western Micronesia...
Yap and Koror experienced light winds and fair weather today due
to a northeast-to-southwest oriented surface ridge over the
region. Island heating brought cloudiness over Koror`s interior
sections this afternoon. The uneventful weather pattern will give
way starting Saturday for Yap and Sunday for Koror as the surface
trough moving through eastern Micronesia reaches them.


Marianas Waters...None.


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