Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
258 AM EST Mon Dec 30 2019

Valid 00Z Tue Dec 31 2019 - 00Z Tue Jan 07 2020

Upper ridging to the north and northeast of the region will slip
eastward by Wednesday. Breezy trades on Tuesday will slacken a bit
on Wednesday with isolated showers possible along favored windward
areas. By early Thursday, guidance shows a shortwave reaching
~160W. The 00Z GFS and ECMWF were relatively close to each other
with timing aloft as the Canadian was a bit quicker and the UKMET
a bit slower. This upper trough will support a cold front that
will push through much of the island chain from NW to SE starting
Thursday and likely past the Big Island by late Friday (quicker
ECMWF) or early Saturday (slower GFS). Prefer a solution weighted
toward the quicker side given the trend from 24 hrs ago and
support from the Canadian. Deeper tropical moisture will likely
not get tapped from the ITCZ from the southwest of the area or
southeast, bathing Hawai'i in merely modest showers with the
FROPA. The exception may be on the Big Island per the ECMWF and
GFS, but ensemble support was lacking.

Fracasso