Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
343 AM EDT Wed Jun 16 2021

Valid 00Z Thu Jun 17 2021 - 00Z Thu Jun 24 2021

Most of the latest models and ensembles (though lacking the 00Z
ECMWF today) agree well for the overall evolution through the
period.  Expect a typical trade pattern with winds varying
relative to the southwest extent of eastern Pacific high pressure.
 Today's guidance shows a little better defined oscillation in
strength with time--a weakening trend during the latter half of
the week, a slight rebound into early next week, and then
weakening again toward midweek as a front to the northwest erodes
the west side of the surface high.  The 00Z CMC/CMC mean do not
show this latter weaker trend though.  Trades will provide the
best shower focus to windward/mountain areas but there will be
times when the background flow is weak enough to allow for
land/sea breeze influence on showers.  A couple pockets of
moisture will support slightly above-average precipitable water
values mid-late week.  Then a modest drying trend should lead to
PWATs holding near to slightly below normal thereafter.  Consensus
still shows an upper level weakness closing off a better defined
low just northeast of the islands by Saturday.  This low should
persist through Sunday before being ejected northward by an upper
ridge that builds in from the east.  The upper weakness/low could
enhance showers a bit from the latter half of the week through the
weekend.     

Rausch