Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
827 AM EDT Mon Apr 13 2015

Valid 00Z Tue Apr 14 2015 - 00Z Tue Apr 21 2015

Synopsis---

Split-flow pattern prevails across a large portion of the US
forecast area---from west (the Aleutians) to east (the Gulf of
Mexico northward into New England). The current satellite loop
across the entire Pacific---is beginning to depict some of the key
features of the evolving pattern and global guidance focus this
forecast period (days1-7). 

The water vapor imagery shows a northeastward progression of a
moisture plume from the Tropics---between the Dateline and 160W
longitude. This moisture plume has been a feature of the global
guidance---the southern branch jet axis 'depiction' lifting
northeastward and its brief 'phasing' scenario north of the
Islands at/around the 16/00Z-16/12Z time step. The 13/00Z model
cycle has not wavered much with this scenario---and if
anything---is supportive of compact 500mb vorticity migration
invof Hawai'i days3-4. As has been the case---this time frame may
be the opportunity for some subtle sensible weather change---given
the prevailing split-flow pattern.

Model Preferences/Sensible Weather---

The occasional high cloud and moisture in the southern branch of
this flow (Subtropical Jet) will be at a peak on Monday. On/around
Thursday---remains the best prospects for a period of 'phasing' in
this split-flow pattern. The 13/00Z Canadian solution would be the
more aggressive scenario with its compact closed 500mb low invof
25N 150W @ 17/00Z. The 13/00Z ECMWF solution having a weaker
vorticity center (eddy-like) feature near 19N 160W @ 17/00Z. The
13/00Z GFS carries a trough invof the Kauai Channel @ 17/00Z.
Therefore, would believe shower enhancement has promise---and the
only subtle change in the sensible weather---that seems to be
worth a mention.

Recommend a blend of the 13/00z ECENS, GEFS and NAEFS should
handle the day4-6 (Fri-Sun) portion of the medium range forecast.
The eye remains focused on the evolving mid-level trough
pattern---currently at 49N 175W and shortwave energy beginning to
migrate into the Sea of Okhotsk.

Vojtesak