Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
728 AM EST Sat Dec 10 2016

Valid 00Z Sun Dec 11 2016 - 00Z Sun Dec 18 2016

Ensembles show that troughing to the north/northwest of the region
will sustain a couple more days of showery conditions with some
embedded heaver amounts. Southerly flow will veer to northwesterly
as a cold front associated with the departing upper trough pushes
into the region on Monday and early Tuesday. Blend of the recent
GFS/ECMWF should suffice as timing differences remain (ensembles
generally lag the deterministic by about 6-12 hrs). As that upper
trough and sfc front pull away from Hawai'i, weak/brief ridging
and drier conditions are forecast to overspread the area on
Wednesday and early Thursday. Trades will stay disrupted as the
flow becomes southeasterly then southerly and finally
southwesterly next Friday/Saturday. Ensembles show strongly
digging heights just west of 160W (a bit farther east than 24 hrs
ago) and a strong likelihood of a closed low (potentially deep).
This could set up another heavy rainfall pattern for the 50th
state, though some differences in the GFS/ECMWF ensembles are
evident -- the former were deeper/slower than the latter though
the 00Z deterministic ECMWF was again slower than its ensemble
mean and closer to the 00Z Canadian but not as deep or southwest
as the GFS/GEFS mean. Preference lies with the 00Z GFS/GEFS mean
as the ECMWF forecasts a rather extreme solution, but is not
entirely unreasonable given the setup. These details have yet to
be determined.


Fracasso