Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
815 AM EDT Wed Apr 18 2018

Valid 00Z Thu Apr 19 2018 - 00Z Thu Apr 26 2018

A series of high pressure cells bridging to the north of the state
over the next week will act to periodically reinforce trade flow
across moderate to brisk levels into the islands. Drier air as a
lead surface high slides eastward between 30-35N will retreat over
the next few days as guidance shows a surge in precipitable water
values Thursday as a weak trough aloft moves eastward over the
region. This will act to increase showers and local downpours.
Expect some decrease in PW values again by the weekend. A
preferred composite of reasonably well clustered model and
ensemble guidance shows increasing heights to the northwest of
Hawaii as an upper ridge/closed high strengthens near the Dateline
with heights 1-2 standard deviations above the mean, and the
downstream pattern will continue to favor some windward terrain
trade showers.

Schichtel