Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
809 AM EDT Mon Sep 04 2017

Valid 00Z Tue Sep 05 2017 - 00Z Tue Sep 12 2017

The early part of this week will feature a front that will likely
stall just north of the islands and a weak/elongated surface ridge
that should keep winds relatively light.  As a result expect
shower activity to be influenced by land and sea breeze
boundaries.  Expect Wednesday to serve as the transition to a
period of moderate trades and primarily windward-focused rainfall
late in the week as a high at the surface and aloft builds across
the east-central Pacific.  Then guidance expects trades to trend
lighter late weekend into early next week as the high weakens
while reaching the eastern Pacific and surface low
pressure/frontal system develop to the north in response to an
amplifying upper trough.  By Saturday-Sunday most of the 00z/06z
operational models are more amplified than most 00z ensembles with
the upper trough.  The GFS runs look particularly amplified as
they have extreme to outlier solutions at various height values
for that time frame.  Until ensembles exhibit a trend toward the
operational upper trough amplitude, would recommend leaning
somewhat more toward the ensemble mean forecast late in the
period.  Uncertainty in this late period evolution lowers
confidence in how much lower latitude moisture may reach the
islands from the southeast.

Rausch