Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
809 AM EDT Tue Aug 22 2017

Valid 00Z Wed Aug 23 2017 - 00Z Wed Aug 30 2017

Expect a drier trend after Tuesday as an upper low to the
northwest of the state and area of high precipitable water values
progress to the west.  During mid-late week high pressure to the
north will promote trades of at least moderate strength, yielding
primary emphasis on windward terrain for any light shower activity
that occurs.  Weakening of this high may lead to somewhat weaker
trades over the weekend.  Compared to yesterday guidance is more
similar regarding the arrival of 1.50"-plus precipitable water
values into the southeastern islands early next week.  While this
aspect of the forecast has been resolved for the time being, there
are now differences in how much east-central Pacific upper trough
amplification occurs early next week with effects on the surface
pattern/trade flow.  The more amplified upper trough in the
00z/06z GFS runs is on the extreme edge of the 00z ensemble
spread.  This leads to the GFS runs showing more of a break in the
surface ridge north of the state and interruption of trades. 
Latest GEFS means hint at the GFS scenario but still keep the
surface ridge sufficiently intact to maintain trades to some
extent.  At this time would recommend a non-GFS compromise for
next Monday-Tuesday.

Rausch