Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
813 AM EDT Sun Apr 12 2015

Valid 00Z Mon Apr 13 2015 - 00Z Mon Apr 20 2015

For Hawai'i, the weather forecast and prevailing pattern in the
central Pacific remains rather "stable"---with little model
solution variation in the near term (out to 84 hours). Even with
this unusual and complex split-flow pattern aloft, the wave train
progression in the mid-latitude Pacific has a high level of
predictability.

The occasional high cloud migration in the southern branch of this
flow (Subtropical Jet) begins to lift northward Monday and periods
of the high cloud cover originating in the Tropics should not
create many sensible weather concerns. On/around Thursday---the
best prospects in the medium range period for 'phasing' of this
split-flow pattern---remains an interesting feature in the central
Pacific. In the area of the central Pacific---along 30N between
155W-160W---the 12/00Z deterministic solutions, namely the ECMWF,
GFS and Canadian are beginning to provide a scenario for mid-level
troughing to develop ---in response to---a brief phasing of the
two jet streams. 

At these time frames---the 12/00Z GFS/ECMWF generate the more
prominent vorticity signatures in the Subtropics. The 12/00Z
Canadian---letting the dynamical forcing to pass northeastward
with minimal impacts on the western portion of the state.

Overall, a blend of the 12/00z ECENS and GEFS should handle the
day4-7 portion of the medium range forecast---with an eye on the
evolving mid-level trough progression across the Subtropics along
30N between 170W and 150W. This trough will have origins in
northeast Asia, emerging off the far western Pacific
coast---between Kamchatka and northern Japan. Its parent cold core
circulation---migrating eastward along 50N and reaching 155W on
Wednesday. This may be the only system---of interest---that
provides some subtle sensible weather variation for the central
Pacific and Hawai'i this forecast period.

Vojtesak