Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
735 AM EDT Thu Apr 06 2017

Valid 00Z Fri Apr 07 2017 - 00Z Fri Apr 14 2017

Guidance indicates high pressure moves north of the islands Friday
and then east of the islands Saturday.  A weakness in the low
level ridge develops and even an inverted surface trough as a
front crosses north of the state.  Low level convergence supports
an uptick in shower coverage Sunday night into Monday.  Afterward,
a low to mid level ridge from the northwest gradually builds north
of the islands early to the middle part of next week. 

During next week some detail uncertainties emerge with approaching
upper level shortwave energy with the gfs and gefs mean faster in
moving the low amplitude wave across the island vs the ecmwf and
ecmwf ensemble mean.  This is reflected at the surface by the
gfs/gefs moving the area of high pressure faster to the east. Once
the upper wave arrives, the models signal an increase in available
precipitable water to slightly above normal values, so an increase
in showers in expected.  Given the historic bias of the gfs moving
systems too fast, more weighting should be given to the slower
movement in the other guidance.

Petersen