Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
237 AM EDT Tue May 12 2020

Valid 00Z Wed May 13 2020 - 00Z Wed May 20 2020

Models/ensembles show good consensus that a mid/upper-level ridge
should remain in place across Hawaii and much of the Central
Pacific through the next week. Weakening trades are expected
through midweek as surface high pressure north of the state
weakens and slides southward, relaxing the surface pressure
gradient across the region. As a stronger surface high develops
north of the state once again by the weekend, trades should
return. Ensemble means show good consensus (ECENS/GEFS/NAEFS) that
the upper ridge in the vicinity of Hawaii should strengthen over
the weekend, with means showing the center of the upper ridge
anchored directly over Hawaii by Sun-Mon. This, along with a
somewhat drier air mass, should serve to keep convection
relatively suppressed by that time, with only isolated showers
sticking to favored windward/mauka locations. The ECMWF and GFS
both bring the trailing end of a decaying frontal boundary to
Hawaii by early next week, with somewhat deeper moisture pooled
along the boundary perhaps bringing a slight increase in shower
activity. With the upper-level ridge remaining overhead, however,
and the associated subsidence, would expect that would serve to
limit any significant increase in shower activity associated with
the boundary.

Ryan