Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
724 AM EST Wed Feb 06 2019

Valid 00Z Thu Feb 07 2019 - 00Z Thu Feb 14 2019

Guidance is consistent in showing a steady sharpening of an
initially diffuse shortwave trough aloft as it heads into the main
islands over the next couple days.  Low pressure developing along
a surface trough over the state will lift to the north-northeast
and pull a cold front across the area.  Strong high pressure to
the west will support brisk northerly winds from Friday into the
weekend.  Moisture/rainfall may increase briefly ahead of the cold
front but then much drier air will move in from the northwest,
bringing precipitable water values perhaps as low as 1-2 standard
deviations below climatology.

Model/ensemble clustering has improved dramatically compared to
yesterday for the unusual evolution that would bring a strong and
concentrated deep layer low just northeast of the main islands by
the latter half of the weekend into next week.  The surface low
that tracks north-northeast of the state over next couple days
should interact with the rapidly amplifying central Pacific energy
which consensus shows closing off an upper low near 30N latitude
on Saturday.  Now there is decent agreement that the deep low at
the surface and aloft should drift down to near or a fraction east
of 25N 155W by Monday.  This system will have the potential to
produce strong winds around the western half of the circulation
along with high waves.  Periodic episodes of rainfall are also
possible as the fast moving flow carries bands of moisture across
the region from the northwest.  With this part of the forecast
achieving better consensus, the primary uncertainty now is what
happens to this feature Tuesday-Wednesday as additional energy
amplifies to the northeast.  The most common theme is that the
upper feature should shear out but still leave a fair amount of
troughing aloft and lingering low pressure at the surface.  An
enhanced version of the ensemble means--keeping more low pressure
in the vicinity than the progressive 00Z GFS/FV3 GFS but somewhat
less concentrated than the 00Z ECMWF/CMC or 06Z GFS--appears to be
the best starting point as solutions diverge.  

Rausch