Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
243 AM EST Sat Dec 28 2019

Valid 00Z Sun Dec 29 2019 - 00Z Sun Jan 05 2020

Upper ridging will build over the northwest islands Sunday into
Tuesday. Trades will increase by Monday into Tuesday as high
pressure strengthens north and east of the region (1032-1034mb
Monday) with isolated showers possible along favored windward
areas. By early Wednesday, guidance shows a shortwave passing east
of 170W reaching about 160W by early Thursday. The 00Z GFS/UKMET
were a bit quicker than the 00Z ECMWF/Canadian with this feature,
which should drive a cold front into and through much of the
island chain next Thursday-Friday, perhaps stalling over the Big
Island next Saturday. The ECMWF was most aggressive with the front
and associated moisture compared to the GFS, with the ensemble
means somewhat in between. Expect an increase in showers as trades
veer to southeasterly and perhaps southerly ahead of the front. It
appears that deeper tropical moisture may not be tapped from the
ITCZ even in the stronger ECMWF scenario, but some modest rain is
possible nonetheless, depending on the strength of the system.

Fracasso