Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
759 AM EDT Fri Aug 08 2014

Valid 00Z Sat Aug 09 2014 - 00Z Sat Aug 16 2014

...'Iselle' impacting the Big Island...
...'Julio' expected to migrate near---but north of Hawai'i...

Please refer to the Central Pacific Hurricane Center (CPHC) for
the latest information and updates concerning these tropical
cyclones.

Active weather scenario remains in place through the weekend with
'Iselle' gradually weakening along 20N latitude---west of the Big
Island and 'Julio' maintaining a track parallel, but north of the
Islands. The 8/00Z deterministic GFS/ECMWF closely followed the
CPHC forecast tracks for both systems through 12/00Z.

Although 'Julio' is not forecast to make landfall, the circulation
will affect the northern shores of the entire island chain with
wind, swell and rain bands. The GFS suggests 850mb height and
700mb height anomalies of 4-6 standard deviations (SDs) below
normal during its life cycle as it migrates west of 150W longitude
on Saturday. Meanwhile, the 8/00z ECMWF deterministic guidance
indicated anomalies on the order of 2-4 SDs for the same height
fields (850mb & 700mb).

After 11/12z, the deterministic runs take different approaches
between 155W and 160W longitudes--handling 'Julio'--with the ECMWF
closest to the official CPHC forecast and the GFS, a slower and
northern-side envelope solution.

To the north of 'Julio' the ECENS and GEFS means take
equally-opposite approaches with the amplitude of the long wave
trough across the north central Pacific. By day 7-8, the ECENS
establishes the 'mean' long wave positioning near 170W longitude
while the 8/00Z GEFS maintains the 'mean long wave along 150W
longitude. The 8/06Z GEFS is the middle road-- splitting the
difference. For now, recommend following a blend of the 8/00Z
ECENS-8/06Z GEFS means for days 6-7 to mitigate the wide spread in
the guidance across the north central Pacific eastward to the west
coast of the Mainland.

Vojtesak