Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
758 AM EDT Thu May 21 2015

Valid 00Z Fri May 22 2015 - 00Z Fri May 29 2015

An upper trough/embedded closed low and associated surface system
developing to the northeast of the state will push a cold front
southeastward across the islands Fri into the weekend. 
Precipitable water values should be in the 1-1.25 inch or so range
with best dynamics remaining north of the area so rainfall should
remain in the lighter half of the spectrum.  As this leading upper
system departs, one or more pieces of weaker upstream energy
should reload the mean trough.  While the two runs show different
details aloft by early next week, during Mon-Tue the 00z and 06z
GFS both lean to the stronger and southern/southwestern side of
the guidance spread with low pressure to the northeast of the
islands.  Thus a compromise among remaining model/ensemble mean
solutions would be preferable at that time.  Light/variable to
southeasterly winds should prevail prior to frontal passage,
followed by northerly to northeasterly winds for most of the
remainder of the period.  For that part of the forecast expect
mostly light showers focused over windward locales.

Rausch