Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
823 AM EDT Sun Sep 28 2014

Valid 00Z Mon Sep 29 2014 - 00Z Mon Oct 06 2014

Upper ridging currently to the northeast of Hawai'i will build
eastward toward California over the next week. In the west
Pacific, subtropical ridging is forecast to maintain itself
beneath an upper low over northeastern Russia which supports a
strong jet stream (~150 kts) developing off Japan toward the
Dateline. This could allow for a split flow between 170W-160W and
subsequent upper low development just to the north of the 50th
state by late next weekend. The 00Z GFS and ECMWF were well
correlated with this scenario but fall on the deeper side of the
multi-center ensemble spread. The forecast from the 00Z Canadian,
which has clustered near the ECMWF in many recent cases, may be
tainted by an upstream W Pac typhoon forecast that is out of step
with the ensembles at this point. The 06Z GFS is less separated
but seems out of step with the ensembles closer to Alaska.

Net result for Hawai'i should be weaker trades for the middle/end
of this week that should veer more southeasterly which supports
more scattered showers and some thunderstorms. Should the
upper/sfc low form to the north of the state by late next weekend
the winds should continue to veer to southerly as PW values rise.
At this time, would suggest a solution in between the 00Z
GFS/ECMWF and the slightly less intense ensemble means, keeping
the front to the north/northwest of the state by next Sunday (day
7).


Fracasso