Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
716 AM EST Sun Jan 13 2019

Valid 00Z Mon Jan 14 2019 - 00Z Mon Jan 21 2019

Overall there is good continuity in the forecast while guidance
differences for late this week and beyond persist.  During the
first half of the week modest high pressure initially northeast of
the state will produce light to moderate trades, and gradual
weakening/elongation of the surface ridge may promote increasing
potential for sea breezes during the day.  Expect fairly light
windward/sea-breeze focused showers given upper ridging centered
to the southwest of the main islands (rapidly collapsing after
Tuesday) and below average precipitable water values.

With fairly minor spread/run-run variability, guidance still shows
an approaching progressive shortwave trough bringing a front into
the northwestern part of the main islands Thursday and continuing
to the east/southeast thereafter.  Like yesterday the 00Z/06Z GFS
runs appear to be on their own in stalling the front/associated
moisture band over the islands versus consensus (including the 00Z
GEFS mean) which shows a farther southeastward position by
Friday-Saturday.  The 00Z FV3 GFS hangs up the front as well but
does show somewhat more southeastward progress than the
operational GFS runs.  This array of guidance would favor an
average among non-GFS solutions.  High pressure behind this front
will bring a brief period of northerly/northeasterly wind and then
more typical trades.

Another front will come into the picture well northwest of the
main islands by late next weekend.  In this case the latest GFS
runs show greater southeastward amplitude of upper troughing
versus most other guidance (including the GEFS mean), resulting in
a faster front than consensus.  Again would would favor an average
among non-GFS solutions.  By next Sunday expect winds to turn more
from the southeast as high pressure reaches the eastern Pacific
and the front approaches from the west.

Rausch