Area Forecast Discussion
Issued by NWS Pago Pago

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FXZS60 NSTU 010206

Area Forecast Discussion
National Weather Service Pago Pago  AS
306 PM SST Sun May 31 2020

.Discussion...Very convectively active afternoon across the Samoan
Island chain as a surf boundary lingers between Fiji and Tonga,
while marine and land based observations continue to show high
surf along the southern coastlines while easterly winds linger
between 15 and 25 mph. Overall concerns this package will be
lingering wind strengths, rain chances and surf conditions.

The latest IR satellite loop shows a large area of convection
firing in most locations around American Samoa, while extending
way south and west of the region. This area of precipitation has
formed along the sfc boundary between Fiji and Tonga, where the
CIMSS satellite data supports layered PWAT values between 2.25 and
2.50 inches. Additionally, modeled stability and 00z STU
soundings supports unstable atmosphere in place across the entire
region with CAPE over 1200 j/kg and LI around -4. Therefore as
surface wind convergence increases across the island tonight,
(directional and speed convergence), expect numerous rain showers
and isolated thunderstorms to continue to be a threat. Will
mention convective wind gusts in pcpn to be near 30 mph this
evening, as current NWS PPG this afternoon and 00z STU support
this data (winds easterly around 25 from the sfc through 850mb).

Based on the latest vertical wind profile data, easterly gusty
winds will continue across the island to begin the upcoming work
week, as sfc-850mb winds remain southeast to east around 20 to 25
kts, before winds slowly diminish to 15 to 20 kts to end the work
week and into the first of the weekend. The chances for precipitation
will also lessen Wednesday through Friday, as model data supports
significant drying in mid and upper levels during this period.


.Marine...Marine observations showing waves above advisory
criteria with PacIOOS data showing wave heights around 10 ft. NWS
PPG winds through the afternoon have been generally consistently
sustained around 20 kts, with a few gusts over 25 kts in rain
showers. The latest sounding and forecast data supports easterly
winds 20 to 25 kts in a layer from the surface through around 5000
ft, lingering over the coastal waters and keeping seas and winds
above or near advisory level through Tuesday. The surface trough
near Fiji this evening will slowly lift toward American Samoa
keeping good chances for rain through tonight.



A High Surf Advisory is in Effect
A Small Craft Advisory in in Effect



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