Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
211 AM EDT Tue Apr 07 2020

Valid 00Z Wed Apr 08 2020 - 00Z Wed Apr 15 2020

Model/ensemble consensus is good that a deep upper-level low north
of Hawaii is forecast to move northeast away from the state
through midweek, with a trailing cold front expected to weaken as
it slowly passes across the state. The front should eventually
dissipate across the eastern islands by late in the week. PWs of
1.2 to 1.5 will be concentrated in the vicinity of the weakening
surface front through late in the week, which should be sufficient
to focus scattered showers. Light low-level flow will favor mauka
areas for shower activity. Ensemble probabilities suggest minimal
threat for heavy rainfall through late in the week.

Over the weekend, models/ensembles show general agreement that
another shortwave should separate from the Pacific northern stream
and amplify as it moves southeast toward Hawaii, with likely
development of another closed upper-level low north of the state,
and the approach of another cold front. Solutions continue to
differ on exactly how far south the feature will move, and how
deep it will be. At this time, given the spread, something close
to the ensemble means remains the preference until deterministic
solutions come into better agreement on the specifics. Guidance
continues to suggest that the axis of deepest moisture associated
with this feature may remain just east of Hawaii, with the Big
Island perhaps having the best prospect for more significant
showers over the weekend and into early next week. Depending on
how far south the cutoff low tracks, and the strength of the
associated cold front, a period of breezy northwesterly winds is
possible over the weekend and into early next week - although
confidence in such specific aspects of the forecast is relatively
low given the time range and the described guidance variability.

Ryan