463
FXZS60 NSTU 290140
AFDPPG

Area Forecast Discussion
National Weather Service Pago Pago AS
240 PM SST Sun Dec 28 2025

.DISCUSSION...
The latest satellite imageries show deep convections associated
with Invest 99P (99P) concentrated over the Swains Island area.
Light surface winds for 99P together with low vertical wind shear
(10 to 15 mph), and moderate upper-level outflow, makes for a
favorable environment for 99P to further develop as it migrates
east-northeast. Model solutions are also in agreement with moving
Invest 99P east-northeast of the territory as it intensifies
within the next 24 to 48 hours. Upper air observations (RAOB) from
this afternoon (29/00Z) shows an unstable atmosphere with strong
thunderstorm signature, and drier air mass over Tutuila, Aunu`u
and the Manu`a Islands. Thus, expect numerous to widespread
showers with potential thunderstorms and gentle to moderate
southerlies for tonight through at least Tuesday. By early Monday
morning, models are showing the center of 99P northeast of the
Manu`a Islands, posing minimal to no threats to the territory.
Winds will remain at moderate to fresh (15 to 20 mph) southerly
breeze for the Manu`a Islands as gentle to moderate (10 to 15 mph)
southerly winds prevail over the rest of American Samoa through
the end of the short-term forecast period.

As model data projects Invest 99P to migrate further east then
south of the area of responsibility (AOR) by midweek, the trough
line will likely remain north of the territory before migrating
south. Expect scattered showers with light and variable winds to
remain for this period through at least the weekend. By midweek,
model solutions show another low pressure system developing to
the west-northwest of the Fiji Islands and migrating over Fiji as
it intensifies. Models also show a trough to the east-northeast
moving westward simultaneously as the aforementioned low pressure
system. These two features will create a convergence area just
west of the Samoa Islands by Saturday afternoon. Uncertainties in
timing and locations of the features will likely be determined
throughout the forecast period as more data becomes available.

There is a moderate chance for Invest 99P to intensify within the
next 24 to 36 hours.

&&

.Marine...
Combined seas have been observed to remain calm for the last
couple of days. However, abrupt elevation of seas from
thunderstorms embedded within the trough line has prompted an
advisory for small crafts. Models are showing seas to remain
between 5 to 7 feet for the rest of the forecast period.
Additionally, with the center of Invest 99P located just north
and east of the Manu`a Islands, seas are expected to elevate for
the Manu`a coastal waters as moderate to fresh southerly winds
move into the area, tonight. As soon as Invest 99P migrates east-
northeast of the area, seas will also begin to subside for the
Manu`a Islands. Otherwise, seas will likely remain favorable for
the rest of the territory for this forecast period.


&&

.PPG WATCHES/WARNINGS/ADVISORIES...

Small Craft Advisory remains in effect for Swains and the Manu`a
Islands.
Flood Watch remains in effect for Swains Island

&&

$$

JTAllen