170
FXZS60 NSTU 200037
AFDPPG

Area Forecast Discussion
National Weather Service Pago Pago  AS
137 PM SST Sun May 19 2024

.Short term...

Satellite imagery, as of late this morning and early afternoon,
shows a mix of sun and clouds over the American Samoa islands as a
ridge remains dominant over the region and keeping a trough to
the north. A mid-level high to the south of American Samoa will
strengthen through the middle of the week to give a change in the
weather pattern.

From May 1st through this afternoon, WSO Pago Pago recorded 17.98
inches of rainfall. The normal rainfall for the entire month of
May is 11.73 inches. The aforementioned mid level high pressure
system will finally bring below average rainfall from this evening
through the middle of the week. Easterly tradewinds may reach up
to 20 mph at times through Monday, then decrease to up to 15 mph
through Wednesday. Since much drier air along the lower to mid
levels of the atmosphere are expected, this will make it harder
for passing showers to develop. If there is a passing shower
develops, it will be weak considering a strong inversion is
expected at around 3,000 feet (900 mb) by Tuesday and during the
day Wednesday.

Therefore, the risk of passing showers will decrease from
scattered (30-40% chance) to isolated (20% chance) through the
middle of the week. There is high confidence that there won`t be a
risk of flash flooding through Wednesday. Easterly trades will
decrease to around 15 mph, which is well below the Wind Advisory
thresholds for American Samoa.

.Long term...

From Wednesday evening through the rest of the week, we will
monitor a potential low pressure system developing near the Fiji
region and moving well to the south of the territory. Even though
the exact movement of this potential low won`t impact American
Samoa from rainfall within that weather system, it would help
shift winds to become northeasterly and help drag a trough from
the north over the territory. This create conditions that would
favor above normal rainfall through the weekend. At this time, any
potential rainfall will not be strong enough to create flash
flooding over the region.

&&

.Marine...

Rough and choppy conditions continue over the American Samoa
coastal waters region as fresh to strong easterly trades remain.
However, a surface ridge of high pressure that is currently over
the region will weaken as it begins to move away from the region
tonight. The easterly breeze is expected to become a moderate to
fresh breeze for early in the week and becoming an easterly
moderate by late in the week. The wind driven conditions are
currently the primary reason of the rough and choppy conditions as
there are no significant swell anticipated to move through the
region for the next 5 days.

Therefore, sea heights are forecast to slowly ease throughout the
week but is still expected to remain rough through around Tuesday
night and Wednesday. The High Surf Advisory remains in effect
through Tuesday night. The Small Craft Advisory may be set to
expire on Wednesday, but confidence is higher that later in the
week would be when conditions will fall below the Small Craft
Advisory threshold.

&&

.PPG WATCHES/WARNINGS/ADVISORIES...

A High Surf Advisory remains in effect through Tuesday Night.
A Small Craft Advisory remains in effect.

&&

$$

LaPlante