Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
726 AM EST Sun Dec 17 2017

Valid 00Z Mon Dec 18 2017 - 00Z Mon Dec 25 2017

...Heavy rain threat next week...

An upper low will continue to weaken while gradually lifting
northeastward away from the Islands on Sunday, but then an
amplifying longwave trough is expected to align over the State
while a downstream ridge builds off the California coast early to
mid week.  A rich supply of deep tropical moisture (precipitable
water values 2 to 3 standard deviations above normal) ahead of the
leading cold front will heighten the threat for heavy rainfall
while the boundary presses south/southeastward through the Islands
Tuesday and Wednesday.  The threat for heavy rain should diminish
late in the week once the mean through axis and feed of moisture
shift eastward Thursday into Friday.

Deterministic and ensemble guidance continue to show good
agreement with the large scale pattern setting up over the Islands
this week, and are even showing minimal spread with the details of
embedded closed lows within the amplifying longwave trough.  There
also appears to be above average agreement with the timing of the
trough axis shifting eastward late this week/next weekend..


Gerhardt