Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
804 AM EDT Sat May 27 2017

Valid 00Z Sun May 28 2017 - 00Z Sun Jun 04 2017

The surface ridge initially to the northwest of the state will
weaken considerably over the holiday weekend, leading to a period
of rather weak trade flow and thus greater land/sea breeze
influence on rainfall.  Models agree that an upper level shortwave
will cross the area Saturday-Sunday.  This feature may encourage
local enhancement of rainfall a little more than suggested by
guidance within a background of near-normal precipitable water
values.  From late Monday into midweek eastern Pacific high
pressure will build westward, bring trades up to moderate
strength.  Trades should persist at similar or just slightly
weaker strength into Saturday as the surface high returns
northeastward.  Thus expect shower activity to have more of a
windward focus by the Tuesday-Saturday time frame.  From early
week onward guidance is about evenly split regarding eastward
progression of the weekend shortwave.  Latest GFS/GEFS mean/UKMET
runs hold the feature near 150W for a while in contrast to the 00z
ECMWF/ECMWF mean and CMC that carry it well away from the islands.
 The weaker CMC mean has elements of both.  Compared to their 12z
runs the latest GFS/ECMWF are both somewhat slower, so at the very
least timing that is slower than the ECMWF cluster to some extent
(GFS/ECMWF compromise) may be the best solution at this time.

Rausch