Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
759 AM EDT Sun Apr 19 2015

Valid 00Z Mon Apr 20 2015 - 00Z Mon Apr 27 2015

High pressure tracking to the north of the state Sun-Mon and then
settling over a position to the northeast should support several
days of fairly strong trades.  Primarily windward focused showers
should be lightest through Mon given forecast precipitable water
values around or below an inch and presence of an upper level
ridge in the vicinity.

From Tue onward guidance clustering has improved dramatically with
respect to an anomalously deep/southward closed low expected to
reach a location to the south of 30N and west of 170W.  This idea
was best indicated 24 hours ago by the ECMWF/ECMWF mean and GEFS
mean.  Based on current consensus this system will be sufficiently
far west to keep an associated axis of enhanced deep moisture to
the west of the state and allow for maintenance of southeasterly
or east-southeasterly trades through next weekend.  Another
surface high crossing the central Pacific may serve to reinforce
the surface gradient by next Sun.  Coverage and intensity of
rainfall by late week and next weekend may be no greater than what
is expected around midweek, as PWATs should remain no higher than
1-1.25 inches or so and most guidance suggests that the upper
ridge just northwest of the islands midweek may drift back over
the islands thereafter.

Rausch