Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
815 AM EDT Mon Mar 25 2019

Valid 00Z Tue Mar 26 2019 - 00Z Tue Apr 02 2019

From the large scale perspective guidance is similar in showing
that the state will be on the southern fringe of mean troughing
aloft that becomes established over the east-central Pacific.  A
leading vigorous shortwave passing by to the north will push a
cold front into the main islands by Thursday.  By the weekend and
early next week guidance diverges for the exact shortwave details
aloft--which have low predictability due to their small scale. 
These details will determine where the weakening front, likely to
stall over the main islands, is located at any particular time. 
During Saturday-Monday there is little in the way of clustering
evident for shortwave specifics among the operational models and
ensemble means so confidence is low in any specific solution. 
Next Monday another front should come into the picture off to the
distant northwest.  A consensus/compromise forecast should provide
a reasonable starting point while awaiting better agreement on
details mid-late period.

Weakening high pressure initially to the northwest of the state
will track southeastward into Tuesday and then accelerate eastward
as the cold front approaches Wednesday-Thursday.  As a result
expect moderate to brisk trades with windward/mountain showers
early in the week followed by lighter winds and a land/sea breeze
focus for rainfall by midweek.  Most rain should be on the lighter
side of the spectrum.  The arrival and stalling of the front may
provide some enhancement of rainfall though guidance does not
expect precipitable water values to increase much above normal. 
Trailing high pressure will bring in northerly and then
northeasterly winds late week into the weekend.  The high will
likely track north of the area during the weekend.  Once the high
passes, low level flow should turn southeasterly and promote some
return of moisture (to modestly above climatological values) into
the southeastern islands Sunday-Monday.

Rausch