Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
409 AM EDT Fri Mar 13 2020

Valid 00Z Sat Mar 14 2020 - 00Z Sat Mar 21 2020

...Heavy rainfall threat next week...

A front/trough crossing the main islands late this week should
stall and then return westward during the weekend.  This feature
will provide a focus for showers of varying intensity at least
into Saturday.  Then guidance continues to show development of a
Kona low as amplifying shortwave energy west of the area closes
off by Sunday night-Monday.  Current consensus shows the low
persisting through midweek followed by a northward drift as it
opens up Thursday-Friday.  This system will likely focus an axis
of abundant moisture over at least the western and central islands
for multiple days, with anomalies possibly exceeding three
standard deviations above normal for a time.  Operational models
are showing fairly strong signals for multi-inch rainfall totals
that could be sufficient to pose a flash flood threat.  As
expected the ensemble means are somewhat lighter but still quite
heavy compared to their typical output.  There continues to be
some spread on exact location of the heavy rain axis from day to
day, with primary emphasis on the western and central islands. 
The eventual opening up/northward motion of the upper low should
lead to somewhat less extreme rainfall totals toward
Thursday-Friday but lingering moisture may be enough to produce
lingering bands of moderate-heavy activity.  Beyond the rainfall
threat, the Kona low should also produce a period of strong winds
over the western islands early in the week.  Overall an average of
the operational 00Z models would appear best for depicting this
system, given their finer detail relative to the ensemble means
that show a farther northward path for the upper low.  The 00Z
GEFS mean is close to the operational runs around Monday-Monday
night though.

Rausch