Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
354 AM EDT Tue May 30 2023

Valid 00Z Wed May 31 2023 - 00Z Wed Jun 07 2023

Guidance continues to show a trade pattern through the period,
with wind speeds likely to peak in the moderate to brisk range
around Wednesday-Thursday, and then fluctuate through the weekend
into next week.  Models/means have trended toward a central
Pacific front putting more of a dent in the supporting surface
ridge during the weekend than forecast 24 hours ago, though
consensus suggests that the 00Z GFS could be overdone with the
front's effect.  Thus trades may be a little stronger than seen in
the GFS during that time frame.

Precipitable water values should be above climatology at least
through Thursday, in association with an east-west weakness over
or just north of the main islands.  While some weak troughing
should persist over and west-southwest of the state after the
initial weakness dissipates, there is now somewhat better
clustering toward a drier trend from Friday onward.  The ECMWF
continues to be most aggressive in that regard, in a couple
localized cases bringing PWATs near or slightly below an inch, and
the 12Z ECMWF mean is near or below 1.25 inches.  The GEFS mean
has made a noticeable drier trend, now providing more support for
leaning away from the 00Z GFS that keeps more moisture near the
Big Island for most of the period.  Given the trends in moisture
over the course of the period, expect showers to produce the most
rainfall between now and Thursday with a gradual lighter trend
thereafter.  The trades will support primarily windward/mountain
focus for showers though rain could occasionally stray to other
locales.

Rausch