Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
810 AM EDT Sat Jul 21 2018

Valid 00Z Sun Jul 22 2018 - 00Z Sun Jul 29 2018

The overall forecast has not changed much with the arrival of
latest model/ensemble data.  Albeit with some modest variability,
generally expect trades to be moderate to occasionally brisk
through the period.  This will tend to favor windward locations
for shower activity.  There is good continuity with the idea of a
patch of enhanced moisture moving into/across the area from east
to west Sunday-early Tuesday, possibly accompanied by a weak
surface trough.  This increase of moisture and surface feature may
serve to increase rainfall somewhat and encourage rainfall to
reach leeward locales at times.  However expect enough upper level
ridging to be in place to keep activity from being too heavy. 
Behind a narrow area of drier air late Tuesday-Wednesday, the
guidance still differs over how high precipitable water values may
rebound with GFS/GEFS solutions continuing to be a little higher
than the ECMWF.  Even with this continued spread for PWATs there
seems to be some convergence for indicated rainfall potential--in
the lighter portion of the spectrum which seems consistent with
most guidance that shows a gradual strengthening of the ridge
aloft.

Rausch