Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
718 AM EST Wed Feb 14 2018

Valid 00Z Thu Feb 15 2018 - 00Z Thu Feb 22 2018

Latest guidance maintains fairly good continuity from yesterday,
with a mean trough aloft supporting unsettled weather while
preventing establishment of trade flow as a corresponding surface
trough prevails over the islands for most of the period.

Model and ensemble consensus still shows a deep upper low
initially northwest of the state tracking north of Kauai by
Thursday and then opening up/lifting northward as upstream energy
approaches.  Expect this evolution to support a period of enhanced
focus of deep moisture with an axis of heavy rainfall potential
and possible embedded convection drifting from west to east across
the state during mid-late week.  Moisture and rainfall will likely
linger over/near the Big Island as initial dynamics depart and the
mean trough begins to reload.

Guidance is consistent in depicting the closure of another upper
low by Sunday-Monday within the reloading upper trough, with a low
track over or very close to the islands.  As this occurs
moisture/rainfall may return westward for a time and a weak low
may form along the north-south surface trough over the area.  As
was the case yesterday, the 00z CMC upper low track is a little
south of most other solutions though its mean is similar.  Also
the 00z/06z GFS continue to show a deeper feature than other
guidance with a higher percentage of 00z GEFS members than ECMWF
members offering support for the GFS depth.  Only one farther
north CMC ensemble member has a 570 dm height contour.  Based on
the current array of guidance would prefer an upper low depth at
least halfway toward the 00z ECMWF and GEFS/ECMWF means versus the
deeper GFS.  Most guidance has this upper low weakening and/or
lifting away next Wednesday but presence of a strong ridge over
the mid-latitude Pacific makes it more difficult to determine its
direction of motion.  Expect the circulation around the upper low
to bring in somewhat drier air from the west by Tuesday-Wednesday
though the feature will likely maintain some instability over the
area into Tuesday.

Rausch