Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
716 AM EST Tue Jan 09 2018

Valid 00Z Wed Jan 10 2018 - 00Z Wed Jan 17 2018

Guidance continues to be fairly agreeable with at least the large
scale aspects of the forecast.  A narrow shortwave aloft settling
over the islands around Wednesday-Thursday will bring a weak front
with accompanying light rainfall toward Kauai.  This front should
stall and weaken to a trough in the mid-late week time frame. 
Meanwhile the shortwave will draw a separate weak upper feature
and pocket of moisture toward the Big Island, leading to a brief
period of potentially enhanced rainfall over/near the Big Island
primarily around Wednesday-Thursday.  The combination of shortwave
energy will likely depart to the east Friday onward.  A modest dip
in the westerlies will bring another front close to the state
during the weekend but upper ridging building in from the west
should then help to push it back to the north/northeast.  Around
the beginning of next week there is some spread with the northward
extent of moisture, with the 06z GFS farthest north with 1.5 inch
PW values.  The 00z GEFS mean keeps the moisture much farther
south, favoring at least a compromise between the 00z GFS and
ECMWF.  Otherwise, into the weekend lingering surface troughing or
only weak surface ridging should keep winds fairly light, leading
to more sea/land breeze focus for any showers.  By Monday-Tuesday
most models/means (minus the 00z CMC again) maintain the idea that
the surface ridge will become aligned north of the state to
support trade flow, albeit in the lighter half of the spectrum,
and somewhat more windward focus for showers.

Rausch