Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
256 AM EST Sat Jan 14 2023

Valid 00Z Sun Jan 15 2023 - 00Z Sun Jan 22 2023

Latest guidance agrees on a pattern change toward a wetter regime
over the course of the period, as strong upper ridging that
prevails into the first part of next week gives way to a mean
trough aloft northwest of the state.  Through the weekend into the
first part of next week, consensus shows a gradual increase of
moisture reaching the islands from the east but with fairly modest
rainfall given the presence of the upper ridge.  Weak surface high
pressure northeast of the state should favor easterly to
southeasterly background flow but with some land/sea breeze
influence at times.  By midweek, shortwave energy encroaching upon
the weakening upper ridge should bring an initial front fairly
close to the main islands, which could help to increase rainfall
at least slightly.

Then there is still some uncertainty over a trailing front and its
influence on shower activity over the state later in the week,
though with some improvement in agreement versus 24 hours ago.  In
particular by Friday the latest GFS runs have trended toward the
prior consensus that showed higher upper heights over the region
than yesterday's GFS, but GEFS members are still showing lower
heights than other guidance.  Based on the non-GEFS scenario, the
second front may just barely reach the northwestern islands before
stalling/returning north ahead of a stronger upstream front that
may encourage flow over the state to become more southerly by next
Saturday.  The southerly flow would increase moisture/rainfall in
general, while rain ahead of the latter front may also get close
to or reach the northwestern islands.

Rausch