Area Forecast Discussion
Issued by NWS Pago Pago

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FXZS60 NSTU 180201

Area Forecast Discussion
National Weather Service Pago Pago  AS
301 PM SST Wed Jul 17 2019

.Forecast Discussion...

The latest satellite imagery continues to show a line of
convective cumulus clouds to the north of American Samoa. This is
caused by a surface trough as shown on the latest ASCAT reading in
the area. The clouds are moving southward, however there is a
disagreement with the models on the outlook in the next 36 hours.

The GFS shows the trough moving through both Samoa and American
Samoa during the day tomorrow, with a considerable amount of
precipitation throughout the day. However, both the ECMWF and
NAVGEM both show the trough weakening while moving southward
quicker, moving over the territory overnight and getting absorbed
into a mid- level jet between Fiji and the Samoan Islands. Due to
the abundent amount of moisture in all layers of the atmosphere
and instability during that time, we are issuing a Flash Flood
Watch beginning at midnight and lasting 24 hours (through midnight

A weak ridge will enter the territory on Friday and through the
weekend. Models are in agreement with a low pressure system to
develop over Fiji late on Friday, but will move southeastward away
from the region. Isolated to scattered showers are forecast during
this time and to start off next week.



The latest data by the PacIOOS buoy near Aunu`u shows seas around
7 feet with peak periods at 9 seconds. Wave heights are forecast
to subside through the next 5 days to eventually reach around 5
feet Monday. Periods will remain short through the rest of the
week, therefore surf will remain well below High Surf Advisory



A Flash Flood Watch has been issued effective midnight through
midnight Friday.



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