Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
249 AM EST Sat Dec 23 2023

Valid 00Z Sun Dec 24 2023 - 00Z Sun Dec 31 2023

Latest guidance agrees that whatever showers occur next week
should be on the light side with precipitable water values
persistently below climatology.  Light to moderate trades will
prevail during the weekend with a weak surface ridge to the north
and an upper ridge building over the region.  The upper ridge axis
will shift a bit southward after Monday, allowing Pacific systems
to bring a series of fronts close to if not into the main islands.
 This will lead to frequent changes in low level winds and shower
focus in response to each front and trailing high pressure.  The
first front should extend into the islands early in the week, with
its narrow band of moisture settling near the Big Island during
Tuesday-Wednesday and possibly increase rainfall a bit.  Recent
GFS runs have been variable for the next front approaching around
Thursday-Friday.  Some of those runs have been on the amplified
side of guidance for the upper trough, pushing the surface front
southward of consensus.  However the 00Z GFS has adjusted back
toward consensus aloft, yielding better clustering toward this
front's moisture band hanging up just north of the northwestern
islands.  Yet another front should approach next Saturday, with
guidance spread fairly modest relative to typical day 7 forecasts.
 The 00Z ECMWF does get a little amplified with the supporting
upper shortwave at that time, so its front strays slightly
southward versus consensus but not to an extreme degree.     

Rausch