Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
259 AM EST Tue Jan 25 2022

Valid 00Z Wed Jan 26 2022 - 00Z Wed Feb 02 2022

The forecast from now into the first part of the weekend is fairly
consistent and agreeable among the guidance, with a succession of
a couple fronts and trailing highs to the north of the state and
generally near to below average precipitable water values.  Trades
may vary somewhat from day to day while the relatively low
moisture should limit rainfall totals over the typical
windward-favored areas or locally elsewhere if winds weaken enough
to allow for some sea/land breeze influence.

By Sunday through Tuesday, the pronounced divergence in guidance
seen yesterday persists.  GFS/GEFS runs continue to show more
southeastward upper trough amplitude versus other models and
means.  In fact for some 500mb height contours, hardly any 00Z
CMCens/12Z ECens members are as amplified as the 00Z GFS or GEFS
mean.  The deeper and sharper GFS/GEFS upper trough leads to
bringing a significant increase of moisture into the main islands
from the west and south as a front moves in, versus the shallower
upper trough in the majority ECMWF cluster that keeps the front
far enough northwest for the main islands to stay in a
lower-moisture trade regime into Tuesday.  In addition to a
greater proportion of guidance showing the ECMWF cluster,
multi-day trends in the GFS have been toward gradually less upper
trough depth/amplitude and slower arrival of moisture/rainfall. 
This combination seems to favor maintaining a forecast that leans
more in the direction of the ECMWF cluster. 

Rausch