Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
729 AM EST Sun Jan 22 2017

Valid 00Z Mon Jan 23 2017 - 00Z Mon Jan 30 2017

Initially, an elongated, positively-tilted trough will sit across
the northern most islands while gradually shearing in time. Toward
the middle of next week, models agree on establishing longwave
troughing east of Hawai`i with this feature being of no
consequence to the region. Eventually amplified flow in the
mid-latitudes will carry shortwave energy toward 160W next weekend
which may bring a rather well-defined frontal zone through parts
of the island chain. Currently the 06Z GFS is the furthest south
among the available solutions, particularly compared to the
ensemble means. Would stay a bit more conservative and lean toward
the 00Z ECMWF along with the ensemble means.

At the surface, a broad anticyclone to the north will maintain
moderate to occasionally stronger east-northeasterly trades. Such
flow should continue to shift to the more easterly direction as
the dome of high pressure advances toward the east. The resultant
pressure gradient is forecast to continue weakening leading to a
decrease in the local wind fields. By later in the week, warm
advection takes shape in advance of the next system strengthening
across the mid-latitudes. All solutions agree on establishing a
steady period of north-northwesterly flow as cold advection ensues
next weekend. In terms of precipitation threats, the best chance
for showers will be through mid-week given the steady period of
trades. A notable drop off in precipitable water values should
decrease the threat for rainfall thereafter until another chance
arises along the baroclinic zone.


Rubin-Oster