Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
811 AM EDT Sat Jun 16 2018

Valid 00Z Sun Jun 17 2018 - 00Z Sun Jun 24 2018

Today's models and ensemble means show good agreement for the
overall pattern evolution through the period.  From now into the
first half of next week expect trades to be on the light side as a
surface ridge just north of the state will be fairly weak.  A
frontal boundary extending from mid-latitude low pressure will be
responsible for some further weakening of this ridge.  At the same
time an axis of relatively higher precipitable water values will
drop southeastward and settle over or near the northwestern
islands.  Light trades will allow for some land and sea breeze
influence for shower activity.  The greater deep moisture over the
northwestern half of the state may provide a little enhancement to
rainfall but fairly high heights aloft given proximity of upper
ridging to the north/west should keep amounts on the light side.

Later in the week guidance agrees upon a general trend toward
stronger surface high pressure building north of the islands
albeit briefly interrupted by another surface low/front crossing
the mid-latitude Pacific.  This evolution will strengthen trades
to at least moderate levels with drier air moving in from the
east.  Therefore expect more of a windward focus to showers after
midweek.  Amounts should remain fairly light, but with improved
terrain enhancement offsetting the likely decrease in precipitable
water values.

Rausch