Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
822 AM EDT Fri Sep 14 2018

Valid 00Z Sat Sep 15 2018 - 00Z Sat Sep 22 2018

The remnants of Tropical Depression Olivia have moved west of
Hawaii, although some lingering moisture east of the system will
continue to bring showers to the western Hawaiian islands through
Friday night before the deeper moisture moves west of the state.
In general, surface easterlies of 15 to 25 kt will prevail through
the weekend and into next week as Hawaii will largely be under the
influence of upper ridging. By late next week models/ensembles
show general agreement that an upper trough will begin to amplify
across the north central Pacific, with a number of solutions
cutting off an upper low by Thu or Fri. The ECMWF was much farther
south relative to the GFS with this cutoff low, 30N versus 42N,
respectively. At the same time models show a weak easterly wave
approaching Hawaii. The degree of northern stream trough/upper low
amplification north of Hawaii will likely play a role in the
amount of deep tropical moisture that is able to stream northward
into Hawaii in association with the easterly wave and thus the
coverage and intensity of any rainfall. At this time due to the
varying deterministic solutions, and ensemble mean approach is
preferred by late next week.

Ryan