Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
644 AM EST Tue Mar 07 2017

Valid 00Z Wed Mar 08 2017 - 00Z Wed Mar 15 2017

The model forecast a closed mid level low north of the islands
with a trough extending west of the Hawaiian islands.  This allows
deep moisture to remain across the islands mid to late week. 
The pattern changes over the weekend as the low weakens and lifts
northeast, with the upper trough axis
moving east through the islands late in the week and east of the
islands over the weekend.
With a stalling front in the vicinity and deep moisture, scattered
precipitation is expected between now and when the upper trough
passes.

Over the weekend the pattern transitions as the GFS and ECMWF
agree on a low level ridge building north of the islands.  The
northwest portion of the islands dries out even more than the
southeast portion in the precipitable water forecast from both the
GFS and ECMWF, with the layer 1000-500 mb layer humidity dropping
below 50 percent in Oahu and Kauai. The low level winds become
east-southeast with the primary focus for precipitation where the
winds turn upslope in the southeast islands, particularly the big
island.  Coverage in the northwest islands will be isolated next
week as the models show heights building aloft with the ridging
aloft arcing north into the region. The models and ensemble means
indicate this scenario with less than average spread through the
middle of next week.

Petersen