Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
334 AM EDT Mon Oct 17 2022

Valid 00Z Tue Oct 18 2022 - 00Z Tue Oct 25 2022

Over the next couple of days, trade winds are forecast to be light
given a weak pressure gradient, which will allow for a land and
sea breeze pattern to set up over Hawaii. Shower coverage is
likely to be somewhat limited with ridging aloft leading to a
stable airmass. But model agreement has been increasing for a more
active pattern by around Wednesday. Upper troughing moving across
the Pacific should split energy off into a closed upper low by
late Wednesday or Thursday to the north of the state (perhaps
around 30-35N before drifting southwestward). Meanwhile at the
surface, a cold front is likely to track across the northern
islands and stall. This front should provide a focus for moisture
and increased coverage of showers around Thursday-Friday, with the
exact positioning of the front meandering determining where the
highest rain totals could be. Kauai and Oahu appear most likely,
but a moist airmass should be in place farther south as well for
some shower potential. As the upper low drifts west, so will any
remains of the front. But a moist environment could remain into
next weekend with moisture being pulled north from the ITCZ. This
potential for increased moisture is most agreeable for the Big
Island but some guidance like the ECMWF shows the moisture
reaching most of the state. By early next week, a more stable
pattern is forecast to build in, reducing rain chances.

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