Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
257 AM EST Mon Nov 04 2024

Valid 00Z Tue Nov 05 2024 - 00Z Tue Nov 12 2024

Expect a wetter period early this week while moderate trades lead
to primary rainfall focus over windward/mountain locations. 
Guidance has been consistent in showing an area of enhanced
moisture and a surface trough passing through from east to west,
with weak shortwave energy near the western islands as well. 
These ingredients will combine to yield a potential for locally
heavy rainfall, especially over the Big Island.

As has been the case in recent days, guidance details for
specifics diverge after early Wednesday.  The ECMWF, and the ECMWF
mean in more muted form, remain a deep extreme with the tail end
of mid-latitude trough energy that should pull off to the
south/southwest into late week.  The resulting upper low in the
ECMWF persists just east of the state through the weekend and
yields a weaker surface gradient/inverted troughing for a time. 
Other dynamical guidance plus the latest machine learning (ML)
models agree in principle that the upper energy should be
weaker/more sheared near the state, with most of the ML models
suggesting that this sheared energy could finally consolidate into
a weak upper low just south of the main islands by Friday-Saturday
as upper ridging to the north begins to build eastward.  This ML
model cluster favors more of a GFS-type evolution, while a
minority would make the more sheared UKMET/CMC a plausible
possibility as well.  The upper energy/low feature should drift
slowly westward and eventually a little northwest.

Based on the favored GFS or non-ECMWF compromise scenario, a front
should reach close to or into the islands around Wednesday before
stalling, with a drier trend and strong northeasterly winds later
in the week.  Strength of the upper energy/low south of the
islands will determine how much of a rebound in moisture may occur
during Saturday-Monday.  Trades should turn more easterly in this
time frame and remain fairly brisk as supported by high pressure
to the north.

Rausch