Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
829 AM EDT Mon Oct 16 2017

Valid 00Z Tue Oct 17 2017 - 00Z Tue Oct 24 2017

Models and ensembles show generally good agreement on the large
scale pattern across the central Pacific through the next week.
Upper ridge initially northwest of Hawaii will move a bit east
over the Islands as it gradually weakens. Meanwhile, an upper low
well northeast of the state will also slowly weaken over the next
week, having very little in the way of sensible weather impacts
over Hawaii. Low-level east-northeasterly flow of 15-25 kt will
persist across the Islands through most of the next week, as a
surface high remains anchored north of the state. The pattern
across the central Pacific should begin to change by late next
weekend as most models and ensembles show a shortwave amplifying
across the north central Pacific, which could push a cold front
southward in the general direction of Hawaii. There is a fairly
large degree of spread, however, as to the exact evolution of the
trough, and whether a more full latitude trough amplifies north of
Hawaii (as shown by the GFS as well as the GEFS/NAEFS/CMC
ensembles) or whether a somewhat weaker wave moves east more
quickly (as shown by the CMC). The 00z ECMWF was generally in the
middle of these two extremes. Nonetheless, there should be some
type of wave amplifying north of Hawaii by late in the weekend,
which could push a front toward the Islands, but it remains
unclear on how quickly the front will move south toward the
Islands.

Ryan