National Weather Service Raw Text Product

995 
FXZS60 NSTU 200108
AFDPPG

Area Forecast Discussion
National Weather Service Pago Pago  AS
208 PM SST Wed Feb 19 2020

.Discussion...
The active monsoon trough that has been dominating weather
conditions for American Samoa since the weekend is still evident
on satellite imagery this afternoon. Visible satellite show 96P
that was northwest of Savaii yesterday, now to the southeast of
Tutuila. Another area of interest, about 300 miles northwest of
Tutuila, is a feature that is the main reason for the extension 
of the wind advisory. GFS solutions show this feature moving 
across the islands, bringing gusty northwest winds of at least 25 
mph. Current model data diverged from previous runs, moving this 
system across the territory tonight instead of Thursday night. As 
we have experienced in the past few days, the passage of the
system just northwest of Savai'i will bring a lot of showers and 
strong downslope gusts overnight.

Global models continue to keep this active monsoon trough across
the Samoa islands through Saturday. This maintains a favorable
environment for more pulses of rain and windy conditions for the 
territory. Although the monsoon trough is forecast to weaken over
the weekend and shift slightly north in the beginning of the new
week, a ridge building behind it will push it back south toward
the island chain. We will continue to monitor future model runs 
as there is still a lot of uncertainty with this scenario due to 
model skills diminishing beyond day three. However, confidence is
high that as long as the monsoon trough is over or near the 
Samoan islands, we expect numerous to frequent showers, with
thunderstorms likely, and periods of gusty northwest winds as 
these hybrid lows form within the monsoon trough and move along
its axis.

&&

.Marine...
Latest Wave Watch III models depict a diminishing trend in seas 
following a decrease in winds by thursday. This is evident in 
current observations from the Aunu'u PacIOOS buoy showing a swift 
decrease in wave heights since 96 P moved over the islands
overnight last night. However, current model solutions show yet 
another hybrid low moving over the territory tonight. Hence, a 
gale warning will remain as gale forced winds are expected to 
impact surrounding waters through Thursday. Furthermore, seas are
expected to subside even further once the aforementioned low 
moves away from the territory and the threat of weather decreases
through the end of the week.  

&&

.PPG WATCHES/WARNINGS/ADVISORIES...
Gale Warning
Flash Flood Watch
Wind Advisory
High Surf Advisory

&&

$$