Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
256 AM EST Mon Nov 20 2023

Valid 00Z Tue Nov 21 2023 - 00Z Tue Nov 28 2023

Guidance continues to show the same general theme of a variable
pattern between now and early next week.  The front currently over
the islands, with its moisture band helping to support some areas
of enhanced rainfall, will quickly dissipate early this week.
Initially brisk northeasterly winds behind the front and southerly
or variable winds ahead of it will transition back to moderate
trades with windward/mountain shower focus continuing into late
week.  An amplifying and sharpening upper trough west of the main
islands Friday-Saturday will likely continue eastward and bring
another front into the state during the weekend, accompanied by
increasing rainfall and a wind shift from southeasterly to a
variation of northerly.

With guidance finally converging fairly well for the northern
periphery of enhanced moisture that may brush the Big Island
around Tuesday-Wednesday, the primary forecast issue involves
details of the upper trough and surface front affecting the
islands from the weekend into early next week.  The 00Z ECMWF has
trended noticeably slower than its previous run while the 00Z
GEFS/12Z ECMWF means and 00Z GFS all support farther eastward
progress than the 00Z ECMWF.  On the other hand, latest GFS runs
are generally on their own in closing off a compact upper low just
north of the state, albeit with the 00Z run a bit less extreme
than the 18Z run.  The GFS evolution aloft leads to deeper low
pressure lingering north of the area into early next week. 
Progression of the surface front itself is similar to the guidance
majority though.  Thus for the overall forecast at the surface and
aloft, would recommend the GEFS/ECens means and 00Z CMC as well as
12Z/19 ECMWF.  

Rausch