Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
814 AM EDT Sun Oct 20 2019

Valid 00Z Mon Oct 21 2019 - 00Z Mon Oct 28 2019

Flow around the southwest periphery of eastern Pacific high
pressure will bring moderate trades from the east or
east-southeast into midweek.  After Wednesday a front should
approach from the northwest.  Guidance expects this front to
remain northwest of the main islands but be close enough to help
weaken the trades somewhat.  Models/ensembles continue to vary
with details of energy aloft which may briefly close off a low
between 30-40N latitude and support a frontal wave.  Differences
among the GFS/ECWMF/UKMET and the GEFS/ECMWF means do not appear
to have a pronounced effect on the state but the 00Z CMC brings
its overall feature farther east and the front closer to the
islands--a lower probability scenario at this time.  A stronger
mid-latitude trough aloft will come into the picture next weekend
and support another front that approaches from the northwest, with
trades persisting but likely in the lighter half of the spectrum. 
Expect showers to favor windward locations for most of the period
though potential for rain over other areas may increase somewhat
depending on how much the trades weaken late week into the
weekend.  Most solutions indicate a modest pocket of enhanced
moisture will brush the islands early this week and then another
area of potentially higher precipitable water values around
Friday-Saturday and possibly into Sunday (the latter shown by the
GFS/GEFS mean).  

Rausch