Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
717 AM EST Wed Dec 31 2014

Valid 00Z Thu Jan 01 2015 - 00Z Thu Jan 08 2015

Latest model and ensemble guidance agrees upon the idea of an
active weather pattern extending into the weekend with a trend
toward a more typical trade wind regime later in the forecast
period.  The low at the surface and aloft to the north/northeast
of the islands will continue to lift northward with time.  The
trailing cold front initially helping to bring enhanced rainfall
to the Big Island may not be able to make too much further
eastward progress but moisture and rainfall should gradually
decrease over the next day.  Then there is reasonable consensus on
amplification/sharpening of upstream energy into a trough that
should reach maximum depth on Sat, with an associated surface wave
tracking near the islands around late Fri/Fri night.  The majority
cluster indicates the best defined surface feature should track
somewhat farther north than indicated by the 00z ECMWF.  This
system will likely produce enhanced rainfall/possible convection
in the Fri-Sat time frame, with PWATs reaching at least 1.25-1.50
inches and strong dynamics aloft passing over the region.  Passage
of this feature will bring a period of strong northwesterly winds,
finally followed by more typical trade flow by Tue-Wed as high
pressure passes by to the north of the region.  At that time there
are typical differences in details of the surface high and
strength of the gradient to the south but otherwise good agreement
in the overall pattern.

Rausch