Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
700 AM EST Sun Dec 14 2014

Valid 00Z Mon Dec 15 2014 - 00Z Mon Dec 22 2014

An amplified trough east of the island chain has dragged a
weakening frontal boundary across Maui. The latest 06Z surface
analysis showed the baroclinic zone dissipating as a strengthening
surface ridge begins to build north of Hawai`i. At the moment,
light showers were moving westward toward Maui but this activity
does not appear to be reaching the ground.

Moving forward in time, the upper trough east of the islands will
quickly give way to building heights with a 588-mb ridge centered
over Hawai`i throughout much of next week. The accompanied series
of surface highs tracking north of the islands will allow easterly
trades to dominate with low-level winds generally in the 15 to 25
knot range. Wind speeds may be a bit higher today given the
tighter pressure gradient with more of a northeasterly component
given the position of the surface ridge. Looking toward next
weekend, the flow again begins to amplify with pronounced height
falls moving across the International dateline. The 06Z GFS/GEFS
mean are a bit quicker than the 00Z CMC/ECMWF/ECMWF ensemble mean.
The ultimate effect of this system is a shift in the usual trades
as winds begin to veer toward the southeast given the increasing
warm advection. Any precipitation with the approaching cold front
should wait until beyond 21/1200Z. Otherwise, expect scattered
showers given the dominance of the trades next week with a local
focus against the favored upslope terrain. The model preference is
a general model compromise through late next week before shifting
to a combination of the 06Z GFS/00Z ECMWF to account for timing
differences of the next system.


Rubin-Oster