Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
352 AM EDT Sun May 28 2023

Valid 00Z Mon May 29 2023 - 00Z Mon Jun 05 2023

With varying degrees of surface ridging that prevails to the
north, expect a return to typical trade flow with
windward/mountain shower focus for the rest of the week and next
weekend after the departure of a surface trough crossing the state
on Sunday.  Trades should gradually increase in strength during
the first half of the week, reaching moderate to brisk levels by
Wednesday-Thursday, and then may fluctuate modestly thereafter. 
Guidance continues to agree on the establishment of an east-west
upper weakness over or just north of the main islands during the
first half of the week before weakening.  This feature will serve
to raise precipitable water values, with the moisture and lesser
stability possibly helping to enhance rainfall over some locations.

By late week into next weekend there are still some notable
differences in whether the enhanced moisture persists over the
state or drier air moves in from the northeast.  Similar to
yesterday, the 00Z ECMWF shows the most pronounced drying trend
with the 12Z ECMWF mean PWATs drier than the 00Z GEFS mean but not
to the degree of the 00Z ECMWF.  On the positive side, the GFS has
trended away from its very moist solution from 24 hours ago and
for a time brings drier air across the northwestern islands than
seen in the GEFS mean.  Also the models and ensemble means have
become much more agreeable for the shape of late week into weekend
flow aloft.  Consensus now shows nearly all of the approaching
trough energy passing by to the north and east, minimizing the
threat of what had been the wettest side of the envelope.  On the
other hand, the majority of guidance still has a more subtle
trough lingering over/west-southwest of the state into the weekend
and this feature could help to keep moisture levels higher than
depicted by the 00Z ECMWF.  Thus would recommend a compromise
among the 00Z GFS/00Z GFS mean/12Z ECMWF mean for the latter half
of the forecast period.

Rausch