Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
346 AM EDT Sat Apr 18 2020

Valid 00Z Sun Apr 19 2020 - 00Z Sun Apr 26 2020

Today's guidance is consistent in showing a pattern that favors
relatively light shower activity for most of the period, with an
upper ridge aloft over or near the region into Thursday or Friday
and precipitable water values near or somewhat below climatology. 
Models/ensembles diverge for specifics of an upper trough/surface
front approaching from the northwest toward the end of the week,
leading to more uncertainty in the forecast by next Saturday.

From this weekend into next week the combination of high pressure
moving into the East Pacific and a front to the northwest of the
main islands will lead to lighter trades from the east/southeast. 
This would increase land/sea breeze focus for showers.  Around
midweek the front to the northwest of the state will likely
retreat back to the northwest for a brief time.  Then gradual
eastward progression of a sharpening upper trough will likely push
the front back to the east late week into the weekend, possibly
bringing some increase of shower activity to the northwestern
islands by next Saturday.  There is decent clustering at the
surface and aloft into about early Friday.  Then models and
individual ensemble members rapidly diverge for specifics of upper
trough energy and resulting effects at the surface.  Currently the
00Z ECMWF and 00Z GEFS/12Z ECMWF means provide the best
intermediate solution aloft, between the slow 18Z GFS and fast 00Z
run.  The deep upper low that the 00Z CMC tracks to the
north-northwest of the state near 30N latitude does not compare
well to most other guidance. 

Rausch