Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
726 AM EST Sat Dec 27 2014

Valid 00Z Sun Dec 28 2014 - 00Z Sun Jan 04 2015

Thought the 27/00Z ECENS/ECMWF solution more closely follows the
evolving pattern in the mid-latitude and Subtropical central
Pacific eastward to the US Mainland. The primary reason is how
much faster the 27/00Z GEFS/GFS is---incorporating several key
features into the flow pattern---particularly in the Gulf of
Alaska and over the desert Southwest (AZ/NV/SoCal) by day 5 (next
Thursday). At the very least, the 27/06Z deterministic GFS has
slowed down the progression of a closed 500mb low invof 35N 150W
around the 1/12Z time frame. The deterministic 27/00Z ECMWF would
have this same feature closer to 30N 155W at 1/12Z.

Prefer the deterministic ECMWF here. That is---IF---the forecast
was to lean one way or the other with a deterministic outcome at
the day 4-5 time scale. Thought is that it may provide a better
representation of the cloud cover and low-level wind fields for
the mid-level trough passage in 30/00Z-1/00Z time frame.  

The key frame of reference---for the Hawai'i forecast---remains
tied to a mid-level trough migration across Hawai'i between 31/00Z
and 1/00Z. The consolidation of this trough between 150W-160W and
a downstream migration of this energy really is the fundamental
difference---that would lean my preference away from the GEFS/GFS
solution---beyond the 1/00z time frame. The emergence of a closed
500mb low scenario---a feature of both 27/00Z means
(ECENS/GEFS)---adds some confidence that another mid-level trough
will begin to affect the forecast area on Tuesday and spreads
these sensible weather impacts eastward across the entire island
chain on Wednesday.

For the day 6-7...recommend using the 27/00Z ECENS mean for its
consistent forecast approach in the eastern third of the Pacific.

Vojtesak