Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
829 AM EDT Thu Jul 30 2015

Valid 00Z Fri Jul 31 2015 - 00Z Fri Aug 07 2015

Quiet pattern for the next few days as upper ridging drifts
westward through the weekend. Next week, two tropical systems are
forecast to affect the region, at least indirectly. The first is
what is TD 8E which is forecast to dissipate on Friday per the
latest NHC forecast. Its remnant circulation is forecast to drift
west southwestward between 11-15N. However, part of its moisture
will overspread the area -- mostly over the southeastern islands
-- and an increase in rainfall is likely, especially in windward
locations of the Big Island.

The next system on its heels is TS Guillermo. The latest NHC track
takes it to near 18N/146.5W by 06Z Tue 4 Aug, in between the 00Z
GFS and ECMWF. Thereafter, the ECMWF tracks the weakening system
very near the Big Island Wed-Thu while the 00Z and 06Z GFS take it
350 and 200 miles NE of the islands, respectively. The ensemble
systems tended to follow along with their deterministic runs
(ECMWF ensemble mean was closer and weaker to the islands).
Consequently, the ECMWF ensembles forecast much higher PW values
over the SE islands -- generally 2.00-2.50 inches -- midweek next
week while the GEFS ensembles were between about 1.50-2.00 inches.
Ultimate solution depends on the strength of the system and how
the upper level flow influences its track, which is contingent
upon how new upper ridging forms/evolves near 38N/153W around
Tuesday. May tend to favor the farther east solutions but with low
confidence.


Fracasso