Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
810 AM EDT Thu Sep 11 2014

Valid 00Z Fri Sep 12 2014 - 00Z Fri Sep 19 2014

...Synoptic-Scale Overview...
The 11/00Z forecast did not disappoint with respect to the
synoptic-scale pattern emerging over the northern Pacific. The
overwhelming theme in the ensembles and deterministic runs
continues to be the absence of a subtropical ridge axis northeast
of the Hawaiian Islands. For the most part, the subtropical ridge
axis is 'seasonally positioned' in the west and southwest Pacific,
but the eastern Pacific ridge has been displaced in the east
Pacific---anchoring invof 130W-140W across the eastern Gulf of
Alaska and west coast of Canada.

...Model Preferences/Uncertainty Assessment...
Much if not all of the model difference is tied to the very deep
surface cyclone development in the southern Bering Sea and the
intrusion of remnant typhoon 'Fengshen' moisture and energy into
the mid-latitude upper-level westerlies. The most prominent aspect
of the model guidance has been the consistent forecast of the deep
low and its depth/location/timing---ie, a sub 970mb surface
pressure, its emergence just north of the central Aleutians, and
its maximum depth around the 13/00Z-13/12Z time frame.

For Hawai'i, the guidance contained some spread at the surface
beyond 96 hours, but the forecast seems straight-forward. The
ECENS/ECMWF solution is the way to go with respect to the absence
of a 'regular' northeast tradewind--tied to the eastern pacific
portion of the Subtropical Ridge. Through time, recommended a
heavily-weighted 11/00Z ECENS approach with its deterministic
solution handling the slow eastward progression of the western
portion of the Subtropical Ridge along 35N latitude.

...Sensible Weather Highlights...
Light trades, near to slightly above normal high temperatures, and
more diurnal convection appear to be the prevailing weather
features--this 7-day forecast.

Vojtesak