Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
820 AM EDT Mon May 18 2015

Valid 00Z Tue May 19 2015 - 00Z Tue May 26 2015

The 18/00Z ECENS/GEFS and their deterministic runs were good
pieces of guidance heading into day 5 (23/12Z). And thereafter---a
70/30 blend of the ECENS/GEFS or a 60/20/20 ratio of the
ECENS/operational EC/GEFS works for days 6-7.

The remnants of 'Dolphin' were handled 'fairly well' and with a
certain degree of accuracy along 50N latitude --- between (21/12Z
and 23/00Z). Then it becomes a decision --- and subtle adjustment
across the Subtropical central Pacific . Follow the GEFS and GFS
and allow a split-flow to develop along 40N 150W and migrate
downstream. Or follow the ECENS/ECMWF a turn the majority of the
energy northward and amplify the blocky downstream ridge along
western coast of the North America including Alaska.

For 4 days --- the philosophy has been to amplify the ridge and
today will be no different with respect to the deterministic
solution after day 5. Inclusion of some of the deterministic ECMWF
for days 5-7 will allow a 500mb trough to move across northern
Hawai'i offshore water on Friday (day 4) and be progressive.

I can only suggest to leave the better 2 options open here --- use
strictly an ensemble mean approach and/or suggest incorporating
some deterministic ECMWF guidance to detail the smaller-scale
effects of the 500mb trough migration and pattern emerging in its
wake--- beyond day 5.

Vojtesak