Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
818 AM EDT Wed Oct 11 2017

Valid 00Z Thu Oct 12 2017 - 00Z Thu Oct 19 2017

The weather pattern across the Hawaii domain during the short
range period through Friday will consist of a gradually weakening
inverted surface trough slowing tracking westward, with a lesser
magnitude of the trades compared to normal.  This is forecast to
transition to a more zonal flow pattern by the weekend and into
early next week as a large surface high settles southward from
just south of the Aleutians to 35 degrees north by Monday,
becoming established north of the Islands and strengthening the
easterly trade winds owing to the tighter pressure gradient to the
north.  Similar to what was depicted yesterday, both the GEFS and
EC mean continue to indicate the potential for a weak positively
tilted 500mb trough early next week, with a strong upper level
ridge building in northwest of the state.  While greater
differences exist in the more progressive flow pattern across the
northern Pacific, the models are in decent agreement at the lower
latitudes on the synoptic scale.

In terms of expected sensible weather, shower activity is expected
for the favored windward terrain along with gusty easterly winds
beyond Thursday.  A plume of enhanced moisture, with PWs
approaching 2 inches as depicted by the GFS, should be near the
eastern Islands by Friday afternoon and into early Saturday along
with a greater coverage of showers and isolated thunderstorms. 
The deeper moisture should be suppressed to the south by Tuesday
as the ridge advects drier air into the region.

D. Hamrick