Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
355 AM EDT Tue Oct 17 2023

Valid 00Z Wed Oct 18 2023 - 00Z Wed Oct 25 2023

Fairly light trades will prevail through midweek, allowing for
land/sea breeze influence on showers wherever the background flow
is too weak to promote a more typical windward focus.  A front
reaching the northwestern islands after midweek should bring a
narrow axis of moisture into the area with some increase of
rainfall.  Latest model runs suggest that this moisture axis may
break up by the weekend.  Meanwhile high pressure to the north of
the front may help trades to rebound briefly around
Thursday-Friday.

Guidance continues to show significant trough amplification (with
embedded upper low) to the north and west of the state around
Saturday-Monday, perhaps beginning to lift out Tuesday.  The
associated surface front will approach from the northwest and
support southeasterly to southerly winds across the state, likely
pulling up increasing moisture from lower latitudes.  There is
still some spread for specifics, including the precise location of
the enhanced moisture axis, but today's models and means are
noticeably better clustered than yesterday for surface and upper
level details.  The 00Z ECMWF is somewhat deeper than other
guidance with the upper trough around Monday-Tuesday, potentially
playing a role in its forecast of much heavier rainfall over the
central islands next Tuesday.  On the other hand, some other model
runs could be underdone with rainfall to some degree given the
relative consensus among GFS/ECMWF and ensemble mean runs toward
higher precipitable water values by late Monday/Tuesday.

Rausch