Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
358 AM EDT Thu Sep 29 2022

Valid 00Z Fri Sep 30 2022 - 00Z Fri Oct 07 2022

Trades should be on the lighter side of the spectrum for most of
the period, with a dissipating front initially just to the north
followed by a stronger front expected to approach/reach the
northwestern islands by Sunday, and yet another front which by
next Thursday should be more distant to the northwest but still
close enough to disrupt the trades somewhat.  Thus showers may be
from a combination of windward/mountain focus and sea breeze
influence.  Through early next week moisture should range from
below climatology over the Big Island to above normal over the
northwestern islands which will be closer to the moisture
associated with the first two fronts.  GFS/ECMWF runs and the
ensemble means all suggest that the northern fringe of enhanced
lower latitude moisture could reach the Big Island by next
Wednesday or Thursday.

Guidance continues to display some spread and trending for the
exact southward extent of the Sunday front.  Although leading to
an unseasonably early frontal arrival, latest trends have been in
the direction of the GFS which yesterday was on the southern side
of the envelope.  Now the GFS/ECMWF/CMC cluster toward the idea of
a band of enhanced moisture/rainfall reaching the northwestern
islands and the GEFS/ECMWF means have adjusted this way too. 
However the GFS and to some degree GEFS mean are a little
southwest of other guidance for the anchoring system to the
northeast, so there are still some reservations with the exact GFS
scenario.  Later in the period the 00Z ECMWF digs an upstream
upper trough farther west than consensus.  This results in the
ECMWF lifting up the lingering band of frontal moisture more
aggressively via southeasterly flow.  The GFS/CMC and
GEFS/ECens/CMCens means represent the majority pattern by next
Wednesday-Thursday.  

Rausch