Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
208 AM EDT Mon Apr 06 2020

Valid 00Z Tue Apr 07 2020 - 00Z Tue Apr 14 2020

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
through the week. The front should eventually dissipate across the
eastern islands by late in the week. Overall model/ensemble
consensus surrounding these features remains relatively good. 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 flow at the
low-levels will favor mauka areas for shower activity during the
day, and areas near the coast at night. Localized areas of heavy
rain will remain possible through late in the week in association
with the frontal boundary, but ensemble probabilities suggest that
the threat for heavy rainfall should remain quite isolated.

Over the weekend, models/ensembles show general consensus that
another shortwave should separate from the Pacific northern stream
and dive southeast toward Hawaii, with potential development of
another closed upper-level low north of the state. Solutions
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 is the preference until deterministic
solutions come into better agreement on the specifics of the
forecast. 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.

Ryan