Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
344 AM EDT Tue May 4 2021

Valid 00Z Wed May 5 2021 - 00Z Wed May 12 2021

A building trough north of Hawaii will produce a cut-off upper low
near 170 degrees west by Wednesday morning, and then very slowly
track eastward across the western Islands through the end of the
week as suggested by the ensemble means.  This will result in an
inverted surface trough that will tend to weaken the Trades some. 
This feature should lift out as a second trough approaches from
the northwest.  Meanwhile, a large surface high builds in across
the northeast Pacific by the end of the week and into the weekend
near 140 degrees west, and this should increase the Trades some by
the weekend.  By the beginning of next week, the GEFS mean is
suggesting the potential for another upper trough north of the
state, whereas the EC mean has more of a ridge in place.

In terms of rainfall, both the ECMWF and GFS keep the heaviest
rainfall associated with the trough/closed low near the
northwestern Islands.  Elsewhere, typical trade wind enhanced
showers can be expected for the upcoming week, with some
enhancement likely across the Big Island.

Hamrick