Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
707 AM EST Sat Dec 17 2016

Valid 00Z Sun Dec 18 2016 - 00Z Sun Dec 25 2016

Guidance indicates below normal forecast spread and uncertainty
for the upcoming active Hawaiian weather pattern. Satellite
imagery shows an approaching mid-upper level closed low from just
north of the state and a main rainfall focusing front stalling
southeast of the state underneath. High surf warnings/advisories
are in effect for portions of the islands and a high wind warning
is in place for Mauna Loa and Mauna Kea summits today where gusts
could reach 80 mph.

A post-frontal rainfall lull should ramp up late weekend as the
closed low digs over the western islands. The low lingers and
gradually weakens just southwest of the state early next week.
This significant feature has induced a well organized surface low
to tap/pool deep tropical moisture from the southeast as shown in
precipitatble water loops. The heaviest rain threat should focus
over the Big Island with max terrain lift and precipitatble water
values forecast to rise to 1.75". More modest rainfall potential
should build westward across the state early next week before a
drying trend and return of seasonal trades as high pressure
settles well northeast of the state. Models and ensembles are more
varied with amplified late week flow over the mid-lower Pacific
latitudes, but favor subsequent closed low digging farther
westward from the state than the current system concurrent with
subtropical western Pacific ridge retrogression.

Schichtel