Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
301 AM EST Thu Nov 18 2021

Valid 00Z Fri Nov 19 2021 - 00Z Fri Nov 26 2021

After a number of days with a persistent surface trough over the
state, varying degrees of surface ridging to the north of the area
from Friday onward will support a return to more typical trades
with windward/mountain focus for showers.  As seen in guidance
from previous days, a front approaching but not reaching the
northwestern islands could briefly weaken trades over that area
around late Saturday/early Sunday.  Trailing high pressure that
ultimately settles into the East Pacific should promote stronger
trades from Sunday onward.  During the weekend the latest ensemble
means have come close to joining recent GFS/ECMWF runs in
advertising an area of moisture passing by just south of the main
islands.  For most of the period guidance generally shows
precipitable water values staying close to climatology.  The 00Z
ECMWF is the exception in bringing more moisture in from the
east-southeast by around Thanksgiving.  For now would recommend
the majority cluster of the GFS and GEFS/ECMWF means.  There is
still some conflict with specifics aloft as the CMC continues to
show a compact upper low over the islands early in the week while
the ECMWF/GFS are more expansive with the upper ridge centered
northeast of the state.  The ensemble means are less defined with
their ridging, leaving the door open to a modest weakness near the
state, but the CMC still appears to be the lowest probability
solution.

Rausch