Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
821 AM EDT Sat Jul 05 2014

Valid 00Z Sun Jul 06 2014 - 00Z Sun Jul 13 2014

Through day 4...the 5/00z ECMWF-GFS and their respective ensemble
packages maintained good continuity and did not disappoint with
respect to the overall spread of the subtropical high pressure
ridge and a dominant surface cell invof 41N 145W at 9/12Z.

Since both deterministic runs continue to project an impressive
post-frontal strengthening of the surface high invof 41N-42N and
mid-140s W, both could be used without regret with respect to
timing the resurgence of fresh trades across the Islands on and/or
by Wednesday.

In the day 5-7 period however, the 5/00Z forecast cycle yielded
much more uncertainty versus continuity across the northern
Pacific. In particular, the structure of the subtropical ridge
axis and its orientation over the mid-latitude Pacific by 11/00Z.

Much if not all of the challenge is with energy transfer(s) across
the mid-latitude Pacific and related to the replacement of an
exiting upper-level trough in the southeastern gulf of Alaska with
'new' energy emerging in the southern Bering Sea and central
Aleutians. A secondary---but not necessarily a less important
difference---lies across the tropical Pacific on either end of the
mid-level Subtropical Ridge. In short, the Canadian and GEFS
ensembles appear much sharper along 130W beyond day 5 versus the
ECENS. However, the ECENS looks to be too amplified along/west of
the Dateline.

Recommend an equal blend of the 5/00z NAEFS-ECENS to account for
the broad spread on the 'periphery' of the Subtropical Ridge and
anticipate a persistence approach beyond day 5 with the tradewind
circulation until the subtle features---at the surface and
aloft---are better resolved.

Vojtesak