National Weather Service Raw Text Product

151 
FXZS60 NSTU 160149
AFDPPG

Area Forecast Discussion
National Weather Service Pago Pago  AS
249 PM SST Sat Feb 15 2020

.DISCUSSION...
Latest satellite imagery show a very active monsoon trough just
north, edging closer to the Samoan Islands this afternoon. This
intense trough has a disorganized and broad area of convection
that may possibly form into a tropical cyclone.

The current scenario is very complex as multiple drivers are 
involved such as a very strong MJO and SPCZ; leading to global 
models' challenge to resolve an exact location and timing of a 
tropical cyclone center within the trough. Current GFS model  
show multiple lows bringing storm forced winds across the 
territory whereas, EC model solutions consolidate these multiple 
lows into one system to the south of the islands by at least 
Sunday night. However, due to the complexities and the expected 
impacts to the Samoan Islands, similar to TS Gita in 2018, both 
RSMC Nadi and JTWC have issued an advisory for Tropical 
Disturbance 07F (93P) within the monsoon trough (about 800 miles 
northwest of Tutuila), moving it towards the Samoan islands, to
reflect the impacts anticipated for the islands. 

Regardless of the above differences in model data, global models
converge in bringing northwest winds of up to 65 mph with higher 
gusts to impact the territory Sunday and peaking Sunday evening 
through Monday, possibly extending through Tuesday. Hence the 
issuance of a high wind warning for the territory. The timing and 
duration of these damaging winds are likely to vary due to the 
aforementioned model solutions, but we urge that the threats 
associated with a possible tropical cyclone developing within the 
active monsoon trough remains. 

Other than the threat of damaging winds, we continue to see the
elevated potential for flash flooding conditions associated with
the above scenario. We forecast flash flooding condtions to remain
across the territory until Tuesday. 

In the long term, model output show this active monsoon trough
with its embedded low shifting north of the islands. Thus, much
improved weather conditions are expected for the latter half of
the new week. We'll continue to update as newer solutions become
available.

&&

.Marine...
Wave Watch III model solutions show damaging northwest swells 
associated with the active monsoon trough, reaching American Samoa
coastal waters tonight, peaking Sunday through at least Tuesday.
Gale force conditions will also be impacting American Samoa 
coastal waters tonight through at least Monday. Therefore, expect
very rough and high seas with squally thunderstorms, damaging 
heavy swells and coastal floodings, especially during high tides.

&&

.PPG WATCHES/WARNINGS/ADVISORIES...

A Gale Warning remains in effect.
A High Wind Warning is in effect.
A High Surf Advisory remains in effect.
A Flash Flood Watch remains in effect.

&&

$$

JTA/ELM