Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
257 AM EST Thu Dec 24 2020

Valid 00Z Fri Dec 25 2020 - 00Z Fri Jan 01 2021

Latest guidance maintains the theme of recent days, with
reasonable agreement for the surface evolution during the period
but differences apparent at times for specifics aloft and
precipitable water values.  Late this week an approaching front
will settle into the northern islands and its associated band of
moisture may help to enhance rainfall somewhat.  Trailing high
pressure tracking north of the state will strengthen the trades
and favor more windward/mountain focus for rainfall.  Saturday is
likely to have the strongest winds.  Trades will trend weaker and
more southeasterly into early next week as the high continues
eastward and another front approaches but does not reach the main
islands.  Guidance is more diverse with specifics of yet another
front that may approach from the northwest by next Thursday. 
Trades are likely to stay in the lighter half of the spectrum
through that time.  The lighter trades Monday-Thursday may allow
for some sea/land breeze influence on showers.

By the weekend there is still lingering uncertainty over the
specifics of shortwave energy that is most likely to drop from the
southern fringe of the westerlies to some point east of the state.
 A small number of ensemble members from the ECMWF/CMC still
depict the low probability scenario of the energy amplifying over
or closer to the islands such as what the UKMET has been doing in
recent days.  The 00Z CMC/ECMWF are closer to the state than in
earlier runs though.  Meanwhile for moisture this weekend the 00Z
GEFS and 12Z ECMWF means provide a reasonable intermediate
solution between the 00Z ECMWF that shows a pronounced dry push
from the north by early Sunday and 00Z GFS that keeps a pocket of
moisture over the northwestern islands.  By next week there are
other differences in moisture that appear random in nature with
low predictability.      

Rausch