Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
730 AM EST Thu Nov 19 2015

Valid 00Z Fri Nov 20 2015 - 00Z Fri Nov 27 2015

The latest models and ensembles forecast that a series of impulses
will feed into a mean mid-level trough that will linger and be
periodically reinforced to the west-northwest and north of the
Hawaiian Islands over the next week. This will provoke an
associated and prolonged inverted surface pressure trough
response. Trades will gain a more southerly component during the
week and support elevated precipitable water values pooling to
around 1.50-2.00 inches or about +1.5 to +3.0 sigma. QPF from the
models/ensembles remains a mess with lots of spread over the
region. Howevetr, heavier to locally excessive rains should focus
both on the northwestern islands closer to the surface convergence
zone, but also down to the Big Island. There, short term  will
also be prone to locally heavy and terrain enhanced downpours
during the week given extent of pooling moisture feeding into the
region. This is a wet pattern and a flash flood watch has already
been issued by the NWS forecast office in Honolulu for portions of
the Big Island today.

Schichtel