Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
347 AM EDT Sat May 08 2021

Valid 00Z Sun May 09 2021 - 00Z Sun May 16 2021

Guidance continues to show rapid weakening of an upper low
initially centered near the western islands, promoting a drier
trend going into next week.  By mid-late week there has been some
model/ensemble spread for another upper trough forecast to settle
over or just east of the state.  However at the moment there is a
decent cluster among the 00Z GFS/ECMWF/CMC/UKMET and the 00Z
GEFS/CMC means suggesting the trough axis would be over or a
fraction east of the Big Island by Thursday.  This leaves the old
12Z ECMWF mean somewhat farther west than consensus at that time. 
In addition there is better agreement today on precipitable water
values tending to be near to below climatology after the start of
the week.  From this weekend into the first half of next week the
state will be far enough away from central/eastern Pacific high
pressure centers for trades to be in the light to moderate range. 
In the lighter cases there may be some land/sea breeze influence
on showers.  There is good continuity in the signal for
mid-latitude high pressure to strengthen and build southward from
about Wednesday onward, helping to strengthen the trades for the
latter half of the week and promote greater windward focus for
rainfall.  

Rausch