Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
835 AM EDT Tue Oct 23 2018

Valid 00Z Wed Oct 24 2018 - 00Z Wed Oct 31 2018

Recent water vapor imagery shows dry mid-level air streaming in
over Hawaii while a plume of deeper moisture associated with
easterly waves slowly makes its way toward the islands. North of
the Islands is an active mid-latitude flow regime. A cold front is
forecast to approach the northern islands by early Friday morning
before stalling and washing out over the weekend.

Trade winds are expected to be fluctuate from 10-15 kts to
20-25kts as the waves pass south of the islands. Moisture will
once again begin to spread north across portions of Hawaii by mid
to late week increasing chances for rain. Guidance continues to
suggest that the Big Island will be affected by the deepest
moisture associated with the wave by late Wednesday as the wave
passes. Locally heavy rain may be possible.

The global models and the ensemble means are fairly clustered with
the moderate amplitude trough tracking through the north-central
Pacific and the timing of the cold front. As the mid-latitude flow
becomes more progressive, ensembles show general agreement that a
second, similar trough will amplify across the north central
Pacific by Sun-Mon; however is not as clustered as the prior
trough but suggests more potential for additional significant
impacts on Hawaii just beyond the end of the forecast period.

Campbell