Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
220 AM EDT Wed Apr 08 2020

Valid 00Z Thu Apr 09 2020 - 00Z Thu Apr 16 2020

A cold front expected to weaken as it slowly passes across the
state through late this week. PWs of 1.2 to 1.5 will be focused in
the vicinity of the front, which should be sufficient for
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. Deterministic guidance has come into much
better agreement on this feature over the past couple days, and a
general blend of model guidance should represent the feature well,
including any relatively minor differences in frontal timing and
intensity of low pressure north of Hawaii. Guidance continues to
suggest that the axis of deepest moisture associated with this
feature may remain primarily east of Hawaii, with the Big Island
perhaps having the best prospect for more significant showers over
the weekend and into next week as the front likely stalls in the
vicinity. By the middle of next week, as the upper-level system
moves away from the state, ensemble show consensus that
upper-level ridging from the west central Pacific should attempt
to build east toward Hawaii, with heights gradually rising a bit.
This, along with a surface high building north of the state,
should allow for a resumption of a somewhat more typical trade
wind pattern for Hawaii. Guidance shows light trades, on the order
of 10-15 kt, resuming by next Wednesday.

Ryan