Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
807 AM EDT Mon Aug 12 2019

Valid 00Z Tue Aug 13 2019 - 00Z Tue Aug 20 2019

Guidance maintains good continuity/agreement for the expected
pattern evolution but still disagrees over a possible increase of
moisture next weekend and early next week.  During the first half
of the week trades will be light/moderate, likely with a slight
weakening trend between now and early Wednesday.  Some locations
may see an influence from land/sea breezes.  Then into Friday
expect trades to strengthen to more brisk levels as eastern
Pacific high pressure strengthens/moves westward.  This will lead
to greater (though not exclusive) shower focus over windward and
mauka areas by the latter half of the week.  Rainfall during most
of this week should be light given near to below normal
precipitable water values and upper ridging over/northeast of the
area.  For Saturday-Monday the operational models continue to
diverge for precipitable water values with the 00Z ECMWF showing a
couple batches of enhanced moisture reaching the main islands but
the 00-06Z GFS keeping the main islands in an axis of relatively
less moisture.  The GEFS/ECMWF means again provide a good
intermediate forecast of a gradual moisture increase.  Westward
movement of the upper ridge away from the state may also allow for
at least a modest increase of shower activity late in the period.

Rausch