Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
345 AM EDT Mon May 25 2020

Valid 00Z Tue May 26 2020 - 00Z Tue Jun 02 2020

Today's guidance is consistent and similar with the forecast into
late this week.  A weak surface ridge close to the northwestern
islands early this week will promote some land/sea breeze
influence on shower activity, most of which should be on the
lighter half of the spectrum.  The Big Island should continue to
see some trade flow.  High pressure building north of the state
will likely restore trades to at least moderate strength from
Wednesday onward with most showers continuing to be light while
strong ridging aloft prevails. 

During the weekend and early next week guidance still loosely
clusters itself similar to yesterday with respect to evolution on
the northeast side of the upper ridge and a band of moisture that
could drop southward toward the state, albeit with modest effect
on rainfall.  However the 00Z GEFS mean/ECMWF have delayed by at
least a day the arrival of moisture from the north.  This leaves
the 12Z ECMWF mean as the most aggressive and perhaps least likely
scenario given latest trends.  While these trends could give some
merit to the GFS, the 00Z run displaces the upper and surface high
farther east than other guidance from Saturday onward.  Thus would
favor a compromise among the 18Z GFS and 00Z GEFS mean/00Z ECMWF
for the Saturday-Monday part of the forecast.  This solution would
maintain the trade pattern with generally light windward-focused
showers through the weekend into early next week.

Rausch