Area Forecast Discussion
Issued by NWS Pago Pago

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FXZS60 NSTU 230056

Area Forecast Discussion
National Weather Service Pago Pago  AS
156 PM SST Thu Aug 22 2019

.Discussion...Current satellite shows abundant areas of
precipitation firing in large areas generally west of American
Samoa this afternoon. Surface observations from around the island
showing a few rain showers around Pago, while some light showers
pass over the eastern portions of the island. The main forecast
question this package will be centered on the chance of rainfall
tonight and into the weekend.

Once again current satellite data shows abundant convection firing
west of the islands this afternoon in a board area of mid level
theta-e, while a more narrow line of convection fires in a region
of mid level streamline convergence form the northwest and
southwest just south of the office. Current IR satellite trends
show the nearest area of strong convection forming about 400 mile
northwest of the islands. Otherwise, satellite trends show a dry
airmass moving across this islands this afternoon mainly from the
east. The latest mid level theta-e and streamline data shows that
most unstable airmass to linger west and south of the islands this
afternoon and evening, while a narrow ridge of drier and stable
air moves in from the east. This pattern will generate some clouds
with only isolated showers possible tonight. However will
increase the chances of rain showers Friday and into the weekend,
as increasing theta-e (heat, moisture and instability) builds
over American Samoa. Will begin to slowly trend pcpn chances back
toward isolated toward the middle of the upcoming work week as the
latest model data begins to indicate drying in mid and upper lvls.


.Marine...Current marine observations show winds and waves
generally around small craft advisory with 15 to 25kts while
waves slowly creep towards 7ft. Surf heights are around 9 to 10
ft this afternoon as swell periods increase towards 10 seconds.
Overall, will issue a small craft advisory through Friday night
as easterly winds 15 to 20 kts with gusts around 25kts linger over
the region. Will also issue a high surf advisory through Saturday
as wave heights near 8 to 9 feet early Friday while periods
increase to around 12 to 14 seconds.



High Surf Advisory is in effect.
Small Craft Advisory is in effect.


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