Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
730 AM EST Fri Dec 16 2016

Valid 00Z Sat Dec 17 2016 - 00Z Sat Dec 24 2016

...Excessive rainfall threat later weekend/early next week...

The models and ensembles still offer below normal forecast spread
and uncertainty for the upcoming active weather pattern for
Hawaii. Satellite imagery shows an approaching mid-upper level
closed low from just north of the state and a shower focusing cold
front now passing through the southern islands underneath. High
surf warnings and advisories are in effect for portions of the
islands and a high wind warning is in place for Mauna Loa and
Mauna Kea summit elevations above 8000ft where gusts could reach
75 mph. A post-frontal rainfall lull should ramp up this weekend
as the closed low digs over/just to the west of the islands this
weekend. 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. The
increase in low-level convergence combined with strengthening lift
will increase shower/convection coverage. Expect rainfall
potential to build back across the state this weekend and  early
next week before a drying trend through midweek and a gradual
return of trades. The heaviest rain threat should focus over the
southern islands where closed low instability combines with influx
of highest precipitatble water forecast to rise upwards of 1.75".
Cooling aloft is sufficient to also support wintery weather over
the highest summits.

Schichtel