Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
237 AM EST Wed Dec 1 2021

Valid 00Z Thu Dec 2 2021 - 00Z Thu Dec 9 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 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, centered near 160W with good
agreement among the ECENS and GEFS mean.  It appears likely that a
cut-off low will evolve from this trough by Sunday night and
meander just north of the western Islands for a couple of days
before gradually weakening. 

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 3-6+ inches of rain for many areas
for the Saturday through Tuesday time period, with the greatest
totals across windward terrain.  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 Saturday for
the central and western Islands as the front could make it as far
southeast as the Big Island. 

Hamrick