Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
804 AM EDT Thu Oct 10 2019

Valid 00Z Fri Oct 11 2019 - 00Z Fri Oct 18 2019

Model and ensemble guidance continues to agree reasonably well for
the expected pattern during the next seven days.  Through Friday a
band of very high precipitable water values (exceeding two inches,
and as high as 4-5 standard deviations above climatology) will be
crossing the main islands from east to west.  Expect the potential
for areas of heavy rainfall as this moisture band passes through. 
Best rainfall focus should be over southeastward-facing terrain
but activity may also extend to other locations at times.

During the weekend drier air will move in from the east while an
upper ridge moves over and north of the area, so showers will
trend lighter and more scattered.  The southwest periphery of
eastern Pacific high pressure will push a little westward and
allow trades to turn more easterly at some locations.  After the
start of next week the upper ridge will persist to the northwest
of the state, supporting northerly to northeasterly flow aloft
with pockets of moisture crossing the region.  The flow aloft will
help to push a cold front southward toward the islands (at least
as far south as 25N latitude) by next Wednesday-Thursday. 
Forecast differences are generally within typical error ranges for
that time frame so a guidance average would be reasonable for a
single specific forecast.  High pressure behind the front will
likely strengthen the trades somewhat.

Rausch