Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
217 AM EST Wed Nov 29 2023

Valid 00Z Thu Nov 30 2023 - 00Z Thu Dec 07 2023

...Heavy Rain and Flash Flooding possible this week across much of
Hawaii...

There continues to be excellent agreement that a Kona low will set
up west of Hawaii by Thursday, bringing potential for widespread
heavy rainfall and thunderstorms  through Friday to much of the
state. The guidance shows precipitable water values up to two or
more standard deviations above normal, increasing the threat for
flooding and flash flooding. Despite the large scale agreement,
there continues to be quite a bit of uncertainty in the details
which has implications for total rainfall amounts with some of the
guidance suggesting the heaviest rains may actually stay
north/east of the island chain. A general model compromise with
the ensemble means should serve a good starting point for the
forecast. The upper low should weaken and slowly begin to drift
east Friday-Saturday. Rainfall this weekend should trend lighter
across Hawaii, but still some potential for locally heavy rain as
the upper low lingers. Trade winds should shift back easterly and
strengthen early-mid next week as upper ridging builds back in
over Hawaii.

Santorelli