Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
830 AM EDT Sat Sep 08 2018

Valid 00Z Sun Sep 09 2018 - 00Z Sun Sep 16 2018

The forecast the next several days will be driven by tropical
cyclone influences. Initially, a weakening Tropical Storm Norman
is forecast to continue to gain latitude while all eyes move to
Hurricane Olivia. Wind fields should be rather light this weekend,
generally out of the east before the influences of the next
tropical cyclone become more noticeable by Monday. The latest
track from the National Hurricane Center suggests a landfall in
the early morning hours on Wednesday. It would be a tropical storm
at this point but heavy rain, gusty winds, and rough seas are all
likely impacts in spite of the weakening state. Models exhibit
some spatial spread with the 00Z ECMWF being north of the 06Z GFS
with the official track being somewhere in between. Based on this
path, some sustained 30 to 40 knot winds are noted on the northern
side of the circulation with higher gusts likely. It is difficult
to say where the heaviest rainfall will concentrate given model
spread, but the signal exists with the more southern 06Z GFS
forecast primarily impacting the Big Island. After the system
exits west of Hawai`i, a large of dome high pressure sets up
across the central Pacific affording a return to the more
climatologically driven trade winds. Models show them generally in
the 15 to 20 knot range with periods of trade driven showers to
conclude the period.

Rubin-Oster