664
FXZS60 NSTU 120100
AFDPPG

Area Forecast Discussion
National Weather Service Pago Pago AS
200 PM SST Sat Apr 11 2026

.Synopsis...
A ridge of high pressure to the southeast has kept the trough
previously associated with ex - Tropical Cyclone Vaianu to the
south and west of the territory, limiting its impacts locally.
However, this high pressure region is also generating
southeasterly trade winds of up to 20 mph to the east of American
Samoa. These breezy southeasterlies are converging with much
weaker flow further north, creating a clear area of surface
convergence to the east of the territory revealed in this
morning`s satellite wind estimates (ASCAT). This indicates a new
developing surface trough.

.Short term [tonight through Monday night]...
Being in between the two aforementioned troughs has brought an
abundance of atmospheric moisture and instability over the
territory. This is shown in this afternoon`s 00Z RAOB upper-air
sounding. This has brought an increase in coverage of passing
showers to Tutuila Island throughout the morning hours.

Latest model data indicates potential for the developing surface
trough to the east to expand westward near American Samoa tonight
through early next week, increasing rainfall potential to at
least numerous showers. Any embedded heavy showers may lead to
ponding on roadways, especially those in low-lying or vulnerable
areas. Convection associated with this trough is currently
disorganized, and model confidence of convective evolution is
low. As a result, the threat for if and when more widespread
flash flooding may occur is uncertain at this time, but must be
closely monitored given the favorable moist and unstable
environment that is already in place.

.Long term [Tuesday through Saturday]...
The high pressure ridge to the southeast will weaken and move out
of the area by midweek. This will lead to a decrease in the
pressure gradient over the area, hence weakening the nearby
southeasterly winds and surface convergence in the region. With
no other significant synoptic features expected to develop, winds
should become light and variable by mid to late week as rain
chances decrease.

&&

.Marine...
Latest wave observations at Aunu`u buoy show the persistent south
swells continuing to hold wave heights in the 7 to 9 foot range
with peak period times of around 13 seconds. This continues to
support High Surf and Small Craft Advisory criteria, with similar
conditions expected through Monday. Beachgoers are advised
exercise extra caution, follow guidance from local officials, and
avoid locations vulnerable to large surf along south and east
facing shorelines. Inexperienced mariners operating small vessels
are advised to remain in port until the swell weakens. Seas and
surf should subside below advisory levels by Tuesday as the swell
diminishes and winds begin to decrease.

Looking ahead, another long-period southerly swell generated by a
trough near New Zealand is forecast to reach American Samoa`s
shorelines by Thursday. However, the swell is expected to be
small, as wave models (GFS WAVE, ECMWF WAVE, and WAVE WATCH 3)
are showing no significant increase in wave heights with the
arrival of the swell. Therefore, stronger currents are possible
with the long period times, but seas and surf are still expected
to remain below advisory levels Thursday and Friday.

&&

.PPG WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory remains in effect
Small Craft Advisory remains in effect

&&

$$

Barton