Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EST Sat Nov 26 2022

Valid 00Z Sun Nov 27 2022 - 00Z Sun Dec 04 2022

Once again the guidance agrees fairly well through the first part
of next week with significant differences and run-to-run
variability thereafter.  Flow around an initial deep-layer low
northeast of the state will support relatively dry conditions into
the weekend.  Winds should trend noticeably weaker by Saturday,
possibly allowing for some land/sea breeze influence on shower
activity during the weekend.  Consensus maintains a pronounced
northward surge of tropical moisture and energy aloft by around
late Sunday through Tuesday, with precipitable water values
possibly reaching at least 2.0 inches at some locations (with
better 00Z GFS/ECMWF agreement than seen 24 hours ago). 
Standardized anomalies in the GFS/ECMWF and their means reach plus
2.5-4.  Guidance generally agrees on a heavy rainfall threat but
with typical spread for the specifics.  Enough southeasterly
background flow may exist at low levels to provide the best
enhancement over favored terrain on the Big Island, but other
locations could see meaningful rainfall totals as well.

By mid-late week the guidance, if anything, has become even more
diverse than yesterday with respect to the possible upper pattern
over and near the islands along with the resulting surface pattern
and moisture levels.  The one positive trend from yesterday is
that the 00Z GFS has finally hedged back some on the amount of
moisture lingering over or returning across the islands.  Still,
there is enough upper troughing just west of the state in the
GFS/GEFS mean (and sufficiently close proximity of a surface
front) to keep fairly high precipitable water values over the area
or at least the far western islands for most of the period.  On
the other hand the 00Z ECMWF upper pattern is shifted far enough
west that shortwave energy dropping down the east side of the
ridge axis actually leads to a significant drying trend from the
north.  The 12Z ECMWF mean is not as extreme with the drying trend
but is still a lot drier than the GFS/GEFS mean.  Somewhere
between these extremes, expect a gradual reduction in moisture and
rainfall with time along with the eventual return of at least
light trade winds. 

Rausch