Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
800 AM EDT Fri Jul 13 2018

Valid 00Z Sat Jul 14 2018 - 00Z Sat Jul 21 2018

Models continue to show the upper ridge building through the
region during the next few days, in the wake of an elongated TUTT
(Tropical Upper Tropospheric Trough) which slowly consolidates,
becomes less positively tilted, and retrogrades towards the
International Dateline and Papahanaumokuakea Marine National
Monument.  The guidance outside of the 00z Canadian is in good
agreement with this evolution -- prefer a compromise of the 00z
UKMET, 00z ECMWF, and 06z GFS which line up better with the
available ensemble mean solutions. 

Precipitable water values will briefly surge above normal due to
the nearby TUTT interacting with a weak tropical/easterly wave
this weekend, which should cause a requisite uptick in
precipitation chances and coverage.   Trades should freshen in the
wake of the wave.  Worth watching is a weak convective
low/stronger tropical or easterly wave, which has been
consistently forecast for days, which makes its closest approach
to the Big Island on Wednesday or Thursday.  It is unclear whether
or not it will increase moisture/precipitation for Hawai'i -- it
bears watch -- but another freshening of the trades is likely
Thursday into next Friday in its wake.

Roth