Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
717 AM EST Tue Dec 30 2014

Valid 00Z Wed Dec 31 2014 - 00Z Wed Jan 07 2015

Models are in strong agreement in allowing a large amplitude upper
trough to remain over or within close proximity of the islands
through Saturday before eventually progressing eastward.  Slow
progression of the trough is allowed by a reinforcing shortwave
trough that crosses the islands on Saturday...while an initial
shortwave trough accompanied by a cold frontal passage occur later
today and tonight. 

Models show a bit more spread with the shortwave details
however..particularly with the second shortwave trough...with the
00z ECMWF stronger and slightly slower than other deterministic
solutions.  Given relatively poor run-to-run continuity of the
specifics of the ECMWF solution as well as the large ensemble
spread...
prefer an intermediate solution between the ECMWF and the 06z
GFS...which is very close to the ensemble means.

Regarding sensible weather...the impacts are primary associated
with periodic wind shifts accompanying the cold frontal passage
and the reinforcing shortwave trough on Saturday.  Rainfall
chances and amounts appear relatively small with the cold frontal
passage due to the abundance of dry and relatively stable air over
the region.  Saturday's shortwave trough may have a slightly
better chance of producing rainfall for the eastern islands...as
deeper and more abundant moisture may be in closer proximity.

James