Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
357 AM EDT Tue Jul 19 2022

Valid 00Z Wed Jul 20 2022 - 00Z Wed Jul 27 2022

The state will see moderate to occasionally brisk trades during
the period, but with slightly lighter speeds than early this week
as high pressure initially north of the islands settles into the
east-central Pacific by the weekend.  Guidance continues to
suggest that precipitable water values will generally remain below
average for the time of year, but is still showing some mixed
messages over whether an area of enhanced moisture passing by to
the south late this week and weekend will extend far enough north
to reach at least the Big Island.  Some of the differences may
relate to subtle low-predictability detail issues for impulses
within a general weakness aloft reaching the area from the
north-northeast.  ECMWF runs had been bringing some moisture into
the state late this week but the new 00Z run is somewhat more
suppressed, getting closer to the GEFS mean that has consistently
kept the moisture to the south.  The 12Z ECMWF mean leans toward
older ECMWF runs.  The 00Z GFS has introduced a new wrinkle,
keeping the moisture south late in the week but then lifting it up
into the Big Island during the weekend.  Uncertainty over
potentially important details aloft would favor maintaining an
intermediate solution until a better consensus emerges.  So
overall expect fairly light windward/mountain focused showers
through midweek, followed by the possibility for some increase in
coverage and intensity within a portion of the late week/weekend
time frame.  An upper ridge building in from the east from late
weekend into early next week should support a return to mostly
light rainfall at that time.

Rausch