Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
749 AM EDT Mon Oct 07 2019

Valid 00Z Tue Oct 08 2019 - 00Z Tue Oct 15 2019

The model guidance is in pretty good agreement over the course of
the next week depicting a retrograding and gradually amplifying
upper pattern across the south-central and southeastern Pacific. 
In the short term, the upper low currently centered around 35N
150W will slowly lift to the north over the next couple of days. 
An associated old cold frontal boundary stretches across the
northern part of the island chain and may enhance shower activity
a bit, but the dynamics are weakening, so amounts should be
relatively light.  This system's main impact is lighter trades
across the state, so sea and land breezes will have the greatest
influence on the location of showers through Tuesday.  During the
middle and latter part of the week, upper ridging east of the
island will begin to build westward.  This will push a tropical
wave with a large area of deep moisture toward the state, along
with bringing a consequent increase in trades (though out of a
east-southeast direction on account of the tropical wave). Model
precipitable water values reach over 2 inches across the island of
Hawaii by late Wednesday, then overspread the remainder of state
Thursday into Friday.  As a result, a wetter pattern will ensue,
with a chance for locally heavy rainfall, especially across
windward sections.

Over the weekend, with the upper and surface ridge building over
the state, drier air will begin to advect westward as trades
gradually return to normal.  The more stable air mass will result
in mainly dry conditions statewide, though light windward showers
can't be ruled out.  A short wave trough digging southward out of
the polar stream will erode the upper ridge early next week and
likely bring another period of lighter than average trades.

Klein