Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
809 AM EDT Sun Aug 26 2018

Valid 00Z Mon Aug 27 2018 - 00Z Mon Sep 03 2018

...Heavy rainfall/flooding threat persists into early this week as
Tropical Storm Lane weakens and moves westward...

As of the 0900 UTC advisory from the Central Pacific Hurricane
Center, Lane has weakened to the point of barely meeting tropical
storm criteria.  Expect Lane to continue weakening over the next
couple days with the tropical depression and then post-tropical
cyclone moving farther westward away from the islands.  In spite
of Lane's departure the guidance is consistent in showing that
areas of heavy rainfall should continue over the islands early
this week as high precipitable water values persist, with a slow
drift from east to west.  Flow around a strong and massive eastern
Pacific surface high will maintain moderate to brisk trades that
will serve to enhance rainfall over windward terrain.

By mid-late week models/ensembles maintain the idea that flow
aloft between a ridge building near 160W longitude and an upper
low northeast of the state will promote a drying trend with
precipitable water decreasing below climatological values. 
Moderate to brisk trades may still provide some modest shower
enhancement over windward areas.  By next weekend the upper low
should track north of the state with guidance showing better than
average clustering at a position around 25-30N latitude as of
early next Sunday.  Some moisture on the southeast side of this
feature may reach the Big Island and vicinity late in the weekend.
 However guidance suggests that flow around the upper low should
keep greater deep moisture associated with current Tropical
Depression Fifteen-E well to the east/northeast of the state
through next weekend.  Also trades should weaken somewhat next
weekend with the close proximity of the upper low.

Rausch