263
FXZS60 NSTU 030100
AFDPPG

Area Forecast Discussion
National Weather Service Pago Pago AS
200 PM SST Sun Aug 2 2026

.Synopsis...
Today`s observed data indicates active weather to the south of
American Samoa: Latest satellite visual imagery and satellite
wind estimates (ASCAT) observed a well defined strengthening low
pressure center south of Tonga with a cold front extending
through Tonga and towards the Fiji island chain. Low-level cloud
cover with enhanced shower activity is observed along the cold
front itself and also along subtle areas of surface convergence
ahead of it, including near American Samoa.

ASCAT also clearly shows a ridge further to the west, with the
center of it`s high pressure circulation between Australia and
New Zealand. This is currently driving south to southeasterly
trade winds across a large area of the Southwest Pacific Basin
spanning from the northeast coast of Australia to the cold front
near Tonga and Fiji. The weather pattern for American Samoa over
the next 7 days will be driven by these features as they progress
eastward.

&&

.Short term [tonight through Tuesday night]...
00Z RAOB upper-air observation revealed a continued moistening
and destabilization of the atmospheric profile. This has favored
the increase in passing showers along subtle areas of convergence
in the light wind flow. Some showers may be heavy at times and
cause minor flooding along vulnerable roadways and small streams,
but are not expected to persist long enough to cause widespread
flash flooding. This pattern should continue through the
overnight hours and into tomorrow as American Samoa remains
between weather patterns with a light wind flow and unstable
atmospheric profile.

Rain chances maximize late Monday through Monday night as the
primary convergence associated with the cold frontal boundary
moves over American Samoa. south-southeasterly trade winds behind
the cold front will then take over for the remainder of the short
term forecast period to kick off the next weather pattern. The
southerly component of these winds should transport cooler air
from near New Zealand into the tropics (this process is known as
cold air advection), which is expected to drop temperatures to
below average following the passage of the cold front. The trade
winds will gradually strengthen over the remainder of the short
term forecast period as the ridge to the southwest organizes.
Convergences within the strengthening trade wind flow may bring
periods of enhanced shower activity.

Therefore, expect light winds and potential for a few heavy
passing showers to begin the forecast period, followed by passage
of a cold front bringing more persistent rainfall, and then
gradually strengthening southeasterly trade winds and a decrease
in temperatures to close out the short term forecast period.

.Long term [Wednesday through Sunday]...
By midweek, the center of the high pressure ridge is anticipated
to move over New Zealand and quickly strengthen. The ridge should
then begin moving northeastward and closer to the Tropical
Southwest Pacific by the latter half of the week. With a stronger
and closer ridge of high pressure, a trade wind inversion (Layer
of warm, dry, and stable based about 2 to 3 km above the ground)
is likely to develop over American Samoa. This would drastically
reduce the potential for heavy rainfall and localized flooding,
though light, brief passing trade wind showers would still remain
possible. The strengthening ridge is also forecast to bring a
rapid increase in the speed of the trade winds by midweek. As a
result, confidence is increasing in the likelihood of Wind
Advisory conditions by the end of the week. Wind speeds are
currently expected to peak Thursday night through early next
weekend at up to 35 mph with higher gusts possible. Likely land
hazards include loose objects being blown around and difficult
travel for high-profile vehicles. The stronger southeasterly flow
will also result in stronger cold air advection across the region,
which is anticipated to bring well below average temperatures
over the long term forecast period, high temperatures likely
sub-80 degrees.

Therefore, expect strong gusty winds out of the southeast, well
below average temperatures, and rainfall limited to light passing
trade wind showers throughout the long term forecast period.

&&

.Marine...
Seas have subsided at Aunu`u buoy today into the 6 to 7 foot
range, now below Small Craft Advisory thresholds. Seas are
expected to continue to subside into the day tomorrow as winds
become a calm to light flow, with American Samoa remaining in
between weather patterns. This will bring ideal conditions for
mariners and beachgoers alike tonight into tomorrow.

These calm conditions should begin to change by Monday night into
Tuesday as developing trade winds once again build seas into
Small Craft Advisory levels. These trade winds are then projected
to rapidly strengthen by midweek and into the latter half of the
week, becoming a strong breeze by late week. Confidence is
increasing in the likelihood of very large and dangerous seas,
with Warning level surf, by Friday. Given the dangerous marine
and beach conditions that are expected; mariners, beachgoers,
decision makers, and any other parties of interest are advised to
closely monitor future forecasts before conditions deteriorate.

&&

.PPG WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory is cancelled

&&

$$

Barton