Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 721 AM EST Sun Dec 13 2015 Valid 00Z Mon Dec 14 2015 - 00Z Mon Dec 21 2015 A very light and variable wind regime --- and mid-level trough/weak surface wave near 30N 160W should lift northward, and enter the Gulf of Alaska in 2-3 days. In its wake, deep-layered high pressure builds in from the west (aloft) and northwest (surface-based). Mid-period (days 4-6), another rather intense mid-latitude cyclone enters the Bering Sea and migrates to the western Gulf of Alaska---beginning the process of carving out a rather strong long wave trough into the Subtropics (east of 160W longitude). The 13/00Z EC/GFS based guidance sheds some light on the evolving pattern to emerge across the northeast Pacific---a retrograding mid-level trough and anchoring surface ridge along 30N 150W. At this point in time---an ECENS/ECMWF-based solution that is a 'lesser-phased' in the Gulf of Alaska (at day 6) makes more sense aloft (500 millibars) versus the deterministic 13/00Z GFS. Worth watching --- given the flow attempts to become uni-directional (northeasterly) late in this medium forecast 'window' and may drive an increase in the Northeast trades. Either way, deep-layered high pressure is expected to rebuild into the region --- with moderate/brisk trade wind pattern returning mid-week (day3-4). Vojtesak