Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
713 AM EST Tue Feb 12 2019

Valid 00Z Wed Feb 13 2019 - 00Z Wed Feb 20 2019

Rex block pattern is likely to remain in place over the central
Pacific with ridging/upper high just south of the Aleutians and an
upper low very close to Hawai'i that may retrograde westward (or
be reinforced from the north) underneath the ridge. With a
reasonably agreeable 00Z GEFS and ECMWF ensemble mean, the 00Z
ECMWF and Canadian were close to to this idea. The recent GFS runs
were farther northeast with reinforcing troughing but the 00Z GFS
was closer to the consensus than the 06Z GFS.

This scenario would maintain below average precipitable water
values and breezy northeasterly trades as a surface low organizes
to the east of the Big Island late Thursday into Friday. Per the
ensembles, it would track northwestward to the north of the island
chain but keep its moisture surge east of the area until about
next Tuesday. Over the weekend, a stronger circulation would wrap
more showers around the surface low into the islands from the
north (ECMWF) but even the weaker 06Z GFS still indicates this
next week. Trades will be disrupted but try to maintain a
northerly component, dependent on the details/evolution.

Fracasso