Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
250 AM EDT Wed Oct 07 2020

Valid 00Z Thu Oct 08 2020 - 00Z Thu Oct 15 2020

A break in the subtropical ridge east of Hawai'i should allow for
trades to be weak through Wednesday.  The subtropical ridge shifts
from the western Pacific to the north of the archipelago allowing
a return of moderate trade winds Thursday and Friday.  Of some
interest is the guidance latching onto a stronger TUTT
cell/retrograding upper low to the northwest of Marie.  Remnants
of Marie have trended back southward in the guidance, and combined
with the mid-level low to the north, weaken the trades once more
on Saturday before they re-freshen from Sunday onward and perhaps
increase rain chances/bring light precipitation to portions of the
50th state.  At the moment, the guidance advertises the heaviest
rain during the next week to lie just northwest of the main
islands from late Friday into Saturday, though it still appears to
be modest at best -- 0.5-1" areal average amounts.

The guidance is showing more cohesion with an upper trough moving
from near the International Dateline Sunday to north of the
archipelago late next Tuesday (though not with the main cyclone
within it well to the north).  This system should impact weather
in and near the Papahanaumokuakea Marine National Monument as a
cold front moves into the region which should stay northwest of
the main Hawaiian islands and degrade into a shear line by Monday
and next Tuesday.  The outlier at this moment is the 00z GFS which
is the flattest and fastest with the feature as it allows a
tropical cyclone -- Chanhom/16W -- to accelerate quicker than the
other guidance and boot the upper trough eastward.  Currently, the
deterministic guidance is united in a weaker upper trough solution
than the ensemble means, which is rare.   Believe the upper trough
will be stronger than seen in the 00z guidance suite, though not
as strong as the 06/12z ECMWF advertised.

Roth