Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
244 AM EST Tue Dec 26 2023

Valid 00Z Wed Dec 27 2023 - 00Z Wed Jan 03 2024

Today's guidance continues to show a pattern characterized by a
rapid succession of fronts that may affect the main islands,
helping to vary wind direction/speed and shower focus on a
day-to-day basis.  Most rainfall should be on the lighter side as
precipitable water values stay below climatology except for
possibly closer to normal with the front approaching from the
northwest early next week.  An initial band of frontal moisture
settling over the southeastern half of the main islands may
enhance showers a little while the next front settling over the
area by Thursday-Friday may increase rainfall slightly more. 
Guidance has converged better for positioning the Friday front. 
However the next front on Saturday still has meaningful spread. 
The 00Z GFS in particular pushes the front farther south into the
islands due to having a stronger supporting upper shortwave.  The
00Z GEFS mean is close to the GFS in principle aloft but does not
bring the front's moisture band as far south as the GFS, while
other guidance keeps the front somewhat farther north.  The latest
GFS is actually less extreme than some recent runs, so the GFS
moderating trend and persistence of other guidance would favor a
non-GFS compromise for this front.  Then with the front
approaching from the northwest early next week, the primary
difference involves the 00Z ECMWF/CMC pulling off some weak upper
trough energy west of the islands, causing the front to hang up
west/north of the islands versus the 00Z GFS/GEFS/CMCens and 12Z
ECens mean whose broader and more progressive trough lead to the
front reaching the islands.  With the small scale of the ECMWF/CMC
upper feature having low predictability, would favor leaning to
the majority GFS/GEFS cluster until a more pronounced grouping to
the contrary becomes evident.

Rausch