Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
326 AM EDT Wed May 5 2021

Valid 00Z Thu May 6 2021 - 00Z Thu May 13 2021

A building trough north of Hawaii will produce a cut-off upper low
near 170 degrees west  today, 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, both the GEFS and EC
means are suggesting the potential for another upper trough north
of the state.

In terms of rainfall, some enhanced showers and perhaps some
thunderstorms can be expected across the central and western
Islands by the end of the week as the upper low slowly drifts
overhead, and creates some additional instability.  Elsewhere,
typical trade wind enhanced showers can be expected, with heavier
showers likely across the Big Island.

Hamrick