Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
207 AM EST Thu Dec 2 2021

Valid 00Z Fri Dec 3 2021 - 00Z Fri Dec 10 2021

A rather unsettled weather pattern will be in place across the
Hawaii domain over the next week.  A broad closed upper low and
inverted surface trough will initially be present just south of
the state through Thursday night, and this feature becomes
absorbed by a much larger synoptic scale trough dropping south
from near the western Aleutians.  The trough amplifies
significantly by late Friday and into the weekend, forming a
closed low centered near 155W/30N with good agreement among the
ECENS and GEFS mean.  There has been a stronger trend for a closed
low over the past few days of model runs.

The cold front that will accompany this trough is expected to
advect copious tropical moisture northward over the Islands by the
weekend, with the potential for 4-8+ inches of rain for many areas
for the Saturday through Wednesday time period, with the greatest
totals across windward terrain.  Flash flooding will be a concern
going into early next week if these trends continue.  Trade winds
are expected to be weaker than normal through Friday since the
normal high pressure pattern north of the state will be displaced
well to the northwest.  Gusty northwesterly winds are likely by
the weekend for the central and western Islands as the front could
make it as far southeast as the Big Island. 

Hamrick