Area Forecast Discussion
Issued by NWS Pago Pago

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FXZS60 NSTU 160110

Area Forecast Discussion
National Weather Service Pago Pago  AS
210 PM SST Fri Dec 15 2017

.Short term...
imagery shows a surface ridge slowly dissipating across the Samoan
islands. An active area of showers and thunderstorms across
Swains Island and another band to the southwest of the Samoan
islands reflect the South Pacific Convergence Zone (SPCZ)
intensifying over our area. The interesting feature from the SPCZ
for the short term is a low level pressure deepening North of Fiji
which will then move towards the Samoan islands. We anticipate
the potential for flash flooding across the territory Saturday
through the new week. From the aforementioned deepening low,
models are intensifying it, reaching Tropical Depression level
winds Sunday night into early Monday morning. Hence, a wind
advisory will likely be issued for the territory Sunday. We will
continue to monitor the evolution of this system and issue
necessary products if it continues to intensify Sunday night.

.Long term...
MONDAY THROUGH FRIDAY...Current model data moves the above
tropical system back southeast of the territory Monday afternoon
through Monday night. Hence, we anticipate the winds to gradually
diminish to below advisory levels by at least Monday night into
Tuesday morning. However, the trailing trough is still expected to
remain across the Samoan islands through midweek. This keeps the
potential for flash flooding through at least Wednesday night.
Hence, will adjust previous forecast to reflect this scenario.


Latest Wave Watch III solutions show seas and winds remaining
below advisory criteria through Saturday morning. We anticipate
issuing advisories for small crafts and high surfs Saturday night
as the seas and winds increase due to the aforementioned deepening tropical
system heading towards the Samoan islands. Current models show
heights reaching Warning levels by at least Sunday afternoon then
gradually subside to advisory levels by Tuesday.





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