Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
820 AM EDT Tue Oct 10 2017

Valid 00Z Wed Oct 11 2017 - 00Z Wed Oct 18 2017

The weather pattern across the Hawaii domain during the short
range period through Thursday will consist of a gradually
weakening inverted surface trough slowing tracking westward along
with a weak upper level trough.  This is forecast to transition to
a more zonal flow pattern by the weekend and beyond as a large
surface high settles southward from 50 degrees north to 35 degrees
north by the end of the forecast period, becoming established
north of the Islands and strengthening the easterly trade winds
owing to the tighter pressure gradient to the north.  Both the
GEFS and EC mean indicate the potential for a weak positively
tilted 500mb trough during the second half of the forecast period,
with strong upper level ridging 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
to be locally enhanced on the favored windward terrain along with
gusty easterly winds.  The short term portion of the forecast is
expected to be the driest.  By early next week, PWs will likely
increase to near 2 inches as the aforementioned upper trough
advects moisture towards the north, and precipitation chances will
likely increase as a result, especially across the eastern parts
of the Islands. 

D. Hamrick