Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
818 AM EDT Sat Oct 19 2019

Valid 00Z Sun Oct 20 2019 - 00Z Sun Oct 27 2019

Today's guidance is similar at the surface and aloft through
midweek.  From Thursday onward individual models and ensemble
members diverge for specifics of shortwave energy to the north of
the area and then a trailing larger scale western-central Pacific
trough.  This results in differences for leading fronts, but so
far these differences to not appear to have a significant impact
over the main islands.

Trades will weaken a bit over the next day or so as high pressure
settles into the eastern Pacific.  Winds should hold steady on
average (with some fluctuations) into midweek and then weaken a
little more during the latter half of the week/weekend as a front
approaches from the northwest.  Expect mostly light to locally
moderate shower activity, favoring windward/mauka areas but on
occasion straying to leeward locales.  The northern fringe of a
pocket of moisture will pass over the area this weekend and
possibly enhance showers a bit, with precipitable water values
tending to remain near to slightly above climatology thereafter.

00Z ensemble spread confirms the uncertainty that operational
models suggest for the evolution of shortwave energy to the north
of the state late in the week.  Whether the slower/separated 00Z
ECMWF-ECMWF mean or more progressive GFS/CMC turn out to be more
correct, the leading front should remain north/northwest of the
main islands and allow some degree of trade flow to persist.  For
the upstream trough aloft by next Saturday the 00-06Z GFS and 00Z
CMC runs all outpace their respective ensemble means.

Rausch