Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
208 AM EST Sun Dec 26 2021

Valid 00Z Mon Dec 27 2021 - 00Z Mon Jan 03 2022

An anomalously strong high pressure system will remain anchored in
the North Pacific between Hawaii and Alaska through at least the
middle of this week, but should finally weaken and shift southward
by next weekend. Meanwhile, a closed upper low meandering west of
Hawaii should also drop to the south as the overall amplified
upper pattern over the central Pacific begins to break down. Gusty
trade winds should continue through much of this week, with
showers tending to favor the typical windward facing terrain.
Models indicate some sort of amplified trough may move in to the
west of Hawaii by next weekend allowing for a shift in the trades
to a more south/southeasterly direction. This would advect a plume
of deeper ITCZ moisture northward towards Hawaii late this week
and especially next weekend. Amidst plenty of uncertainty in the
deterministic solutions with regards to timing and placement of
the upper trough and surface front, there remains a decent signal
in the guidance for widespread and moderate to locally heavy
rainfall across at least parts of the island chain next weekend.
Both the 00z GFS and ECMWF show potential for several inches of
rain for some areas, but considerable uncertainty tempers
confidence in the forecast at this point.

Santorelli