Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
826 AM EDT Thu Apr 12 2018

Valid 00Z Fri Apr 13 2018 - 00Z Fri Apr 20 2018

An upper ridge and 1032mb surface high pressure to the northeast
of Hawai'i will slide eastward and weaken over the next day or so
as a lingering moisture plume (precipitable water values near or
just over 1.50") drifts northwestward. This will support weakening
trades and scattered generally light (but locally moderate)
showers over favored upslope/mauka areas. Tomorrow an upper low
will form just west of the area (around 162W) and move westward
underneath another upper ridge axis along 165W moving eastward
through the mid-latitudes. This should guide a surface front
toward the northern islands by early this weekend before
dissipating. Ensembles show a brief increase in moisture late
Saturday into Sunday from the southeast before generally shunting
the axis west and southwest of the region next week. After
scattered showers this weekend, lighter/isolated showers are
expected next week as another surface high (near 1040mb early
Sunday) sinks southeastward, increasing trades again. Ensembles
disagree on how much to increase moisture again later next week --
GFS was generally higher than the ECMWF but was on the higher side
(top ~10%) of the multi-center ensemble spread.

Fracasso