Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
345 AM EDT Tue May 11 2021

Valid 00Z Wed May 12 2021 - 00Z Wed May 19 2021

Not much has changed in the forecast over the past day, with
guidance showing varying degrees of trade flow supporting a
windward/mountain focus for showers while precipitable water
trending to moderately below normal values should keep the
majority of rainfall totals in the lighter half of the spectrum. 
Consensus still shows the trades strengthening somewhat after
midweek and remaining fairly brisk into next week as an upstream
high replaces leading high pressure to the north-northeast of the
region.  Through this week and into the weekend the models/means
all suggest a shortwave aloft initially north of the state will
close off an upper low that meanders for a time northeast of the
main islands.  Then by early next week the latest GFS runs eject
the low/trough quicker than other guidance including the 00Z GEFS
mean to some degree.  There are still some questionable aspects to
the GFS handling of mid-latitude flow so preference for the upper
low/trough would go to a compromise among the ECMWF/CMC and their
means, with the GEFS mean agreeable into early Monday before
trending weaker and northeast.  Proximity of the upper low, and
more so the potential southwest elongation of the upper trough as
seen in the non-GFS cluster Sunday-Monday, may support some
enhancement of rainfall at times.  

Rausch