Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
758 AM EDT Mon Jul 02 2018

Valid 00Z Tue Jul 03 2018 - 00Z Tue Jul 10 2018

Latest guidance reasonably agrees that a circulation well-depicted
in satellite imagery to the north of the state will continue to
lift away over the next few days to leave room for a deep layer
high pressure system.  A favored model and ensemble composite
indicates that pressure gradients underneath this high pressure
should support increasing island trade winds to moderate to brisk
levels through Saturday. This coupled with some embedded moisture
could fuel some enhanced windward focusing shower activity across
the state early week through July 4 under a general weakness
aloft.  Thursday appears to be the least active day shower-wise
around the time the ridge reaches its closest approach to the main
Hawaiian islands.

Fabio moving well northeast of the 50th state weakens the
subtropical ridge, causing weakening of the trades from Sunday
onward.  Also contributing to the weakening ridge is a
retrograding upper low/TUTT cell potentially enhanced by mid-level
shortwaves breaking around the east side of the subtropical ridge
near the 140th meridian west.  This mid- to upper-level low along
with the remnants of Tropical Storm Emilia approach the Big Island
Friday into this weekend to lead to enhanced precipitable water
values which should fuel more widespread shower/thunderstorm
activity.  The 00z ECMWF depiction of a stronger upper trough in
the Westerlies weakening the subtropical ridge from the north next
Monday looks too aggressive when based on the remainder of the
deterministic/ensemble mean guidance and is considered a low
probability alternative scenario.

Roth/Schichtel