Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
403 AM EDT Sun May 24 2020

Valid 00Z Mon May 25 2020 - 00Z Mon Jun 01 2020

Guidance shows decent agreement and continuity with the forecast
through about Friday.  For most of the first half of the week
expect a weak surface ridge to remain close to the state, leading
to relatively light winds and some sea/land breeze influence on
showers especially over the northwestern islands.  The Big Island
may hold onto more trade flow/windward shower focus.  Somewhat
stronger high pressure will build north of the area during
Wednesday-Friday and bring a return of at least moderate trades. 
Expect rainfall to be light in most cases though very localized
enhancement could occur at the very start of the forecast period.

By next weekend the models and ensemble means diverge considerably
for the upper ridge that strengthens over the area late in the
week and shortwave energy flowing around it.  On one side of the
spectrum, the 00Z GFS/CMC/CMC mean maintain a strong upper ridge
through Sunday--keeping high pressure in place north of the state
and extending the trade pattern that becomes established late in
the week.  On the other hand the 00Z ECMWF/ECMWF mean/GEFS mean
erode the ridge enough to allow a front and band of enhanced
moisture to drop southward close to or into the islands by next
Sunday.  Thus far recent trends do not appear to provide
meaningful insight as to which scenario may be more likely, so
preference would be for an intermediate solution--perhaps a
somewhat northward-adjusted version of the GEFS mean (for the
surface and moisture forecast) which is the least extreme among
that cluster.   

Rausch