Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
741 AM EDT Fri Sep 01 2017

Valid 00Z Sat Sep 02 2017 - 00Z Sat Sep 09 2017

A low level ridge persists northeast of the islands through the
weekend.  To the northwest of the islands, a slowly approaching
cold front is forecast to only slowly drift southeast towards the
islands over the weekend and into next week.  Increasing tropical
moisture should then support the chance for increasing showers and
thunderstorms, particularly across the western part of the state
where a slow moving plume of high precipitable water develops. 
With the plume of moisture remaining in place through at least the
middle of next week, scattered showers/storms are expected, with
locally heavy downpours possible.

On Tuesday 05 Sept, the models agree a low level ridge builds
north of the islands.  During the middle and latter portions of
next week, the models/ensemble means are in better than average
agreement on the low level high building north of Hawaii.  Trades
should then return to near normal levels during this middle to
latter portions of next week. Also, the front weakens.
Both the 06z gfs and 00z ecmwf show a tropical wave moving south
of the islands mid to late next week. The current rainfall
forecasts show the higher amounts remaining south of the islands.

There remains better than average agreement among the 06z gfs and
00z ecmwf forecasts next week to use a blend of the two to
mitigate differences.

Petersen