Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
359 AM EDT Thu Apr 28 2022

Valid 00Z Fri Apr 29 2022 - 00Z Fri May 06 2022

A slight weakness in the subtropical ridge to the north of Hawaii
should weaken trade winds somewhat over the next few days, but
generally moderate to locally breezy trades are still expected,
along with some windward and mountain showers. High pressure will
rebuild to the north and restrengthen trade winds by the weekend
into much of next week. Meanwhile, upper troughing aloft looks to
come into Hawaii for the latter part of the week and last into
early next week, providing added instability for vertical cloud
development and showers. Model guidance also continues to show a
trend for increasing precipitable water values, with a slight
increase late this week but general agreement for the most
anomalous moisture levels around Sunday-Tuesday. The latest GFS
and its ensemble mean show higher PW anomalies for the
southeastern islands, but the ECMWF and its ensemble mean indicate
that high PWs could reach all islands. Thus these factors combined
will lead to a stronger and wetter trade wind pattern, with more
numerous showers especially for windward and mauka locations but
with some potential to spill into leeward areas as well. There is
some model uncertainty as to when moisture levels will drop next
week, and details of the forecast will continue to be monitored to
refine the timing and placement details of the rain potential
before then.

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