Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
809 AM EDT Tue Sep 22 2015

Valid 00Z Wed Sep 23 2015 - 00Z Wed Sep 30 2015

Expect trades to strengthen somewhat over the next few days as
high pressure tracks southeastward from the central Aleutians
toward 40-45N 150W by Sun-Mon.  Gradual weakening of the high late
in the period may allow winds to slacken a bit, though guidance
diverges with the track of the surface high after early Mon with
the 00z ECMWF/ECMWF mean farthest south.  Guidance expects
precipitable water values initially near 1.75 inches to drift
downward to or below 1.50 inches especially to the northwest of
the Big Island, then increase by next Mon-Tue with moisture
arriving from the east.  Latest ECMWF runs are noticeably more
aggressive with this approaching moisture than GFS/GEFS runs. 
While the magnitude is in question, trends for deep moisture over
the period at least suggest a modest decrease in windward shower
intensity over the next few days with potential for locally
heavier activity increasing early next week.

Rausch