Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
257 AM EST Wed Nov 22 2023

Valid 00Z Thu Nov 23 2023 - 00Z Thu Nov 30 2023

An area of enhanced moisture will drift across the state under
moderate trades during Wednesday-Thursday, with some enhanced
rainfall possible over favored windward/mountain terrain. 
Precipitable water values should decrease by late in the week,
while trades trend somewhat lighter and a little more
southeasterly as a front approaches from the northwest.

Latest guidance has persisted with the idea that the upper trough
supporting the front will split just west of the main islands
during the weekend, with an upper low dropping to the south and
the rest of the trough passing by to the north of the state. 
However there is still notable spread for exact amplitude of the
northern trough, affecting how far south/southeast the front
reaches by early next week.  This 00Z cycle features the GEFS mean
as the amplified extreme aloft and the 00Z ECMWF having the least
amplitude (the latter a notable adjustment from the 12Z run that
was somewhat more amplified aloft and pushed the front farther
south).  Given the range of solutions and shuffling of the models
over the past 12-24 hours--including the GFS not being as far
south with the front as 24 hours ago--current preference would be
for a compromise frontal position into next week.

Then by next Tuesday-Wednesday the guidance maintains its recent
idea of fairly rapid amplification/sharpening of another upper
trough just west of the main islands with surface troughing
possibly setting up near or west of the northwestern islands. 
This pattern would raise the potential for a significant increase
in moisture and rainfall.  Among current guidance, the 00Z GFS
offers the least confident solution as by next Wednesday it
becomes very extreme with the southwestward path of its upper low,
becoming an outlier versus all 00Z GEFS/CMCens and 12Z ECens
members at some height values.  The 18Z GFS leaned to this idea
too but at least its overall pattern was closer to the average of
other guidance and would be preferable to the 00Z run.  Otherwise,
the 00Z ECMWF/CMC and the ensemble means ultimately cluster
decently aloft for a day 7 forecast while the ECMWF/CMC develop
more pronounced inverted surface troughing/low pressure just west
of the main islands.  Ultimately prefer an average of ideas from
the non-GFS models/means to represent the majority evolution and
account for the typically lower predictability of details a week
out in time.  This would produce a wetter pattern than forecast by
the 00Z GFS.   

Rausch