Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
255 AM EST Sun Nov 26 2023

Valid 00Z Mon Nov 27 2023 - 00Z Mon Dec 04 2023

High pressure moving eastward to the north of Hawaii should bring
a brief return to moderate trade wind activity Sunday into Monday
with additional moisture beginning to be drawn northward around
the same time as well as southern stream energy breaks off, closes
off a low west of the state, and then opens up again and advances
eastward around Monday. After this though, models continue to show
excellent agreement on a Kona low setting up west of the state
around mid week with precipitable water values increasing up to
two or more standard deviations above normal by Thursday. This
brings an increased potential for widespread heavy rainfall and
thunderstorms to some or all of the Hawaiian islands
Thursday-Saturday, with potential also for heavy snow in the
highest terrain of the Big Island. However, there remains a lot of
uncertainty in the exact placement of the low, which has
implications for where the heaviest rainfall sets up. The 00z GFS
suggests the heaviest rains may remain northeast of the islands,
while the CMC and ECMWF do suggest some relatively significant
rainfall totals across all/parts of the Hawaiian islands. A
general model blend with the ensemble means should provide a
relatively good starting point as there is good agreement on the
large scale. By next weekend, the guidance shows this low
weakening and slowly beginning to drift eastward over the islands
with rainfall trending lighter with time.

Santorelli