Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
242 AM EST Mon Feb 19 2024

Valid 00Z Tue Feb 20 2024 - 00Z Tue Feb 27 2024

Surface high pressure well north of Hawaii (centered just north of
30N) will promote easterly trades likely starting out on the
breezy side Monday. Limited moisture is in place given a ridge
aloft and the post-frontal airmass, but a few showers are possible
in windward locations, especially for the Big Island and Maui per
the HREF. The surface high is forecast to gradually weaken
Tuesday-Wednesday while diving southeast, causing winds to
decrease to more moderate levels. Any showers should stay limited
through midweek.

By the latter half of the week, trades look to strengthen and
possibly veer a bit more southeasterly. This is in response to
another surface high well north of the state while upper and
surface lows develop well west of the islands. Model guidance
varies with how close the surface low/frontal system edge toward
the state by late week. ECMWF and CMC runs have trended a bit west
compared to a day ago, with the moisture plume just ahead/east of
the cold front staying west of the northwestern islands with its
heavy rainfall amounts. The GFS maintains its western position.
But the ensemble members show enough variability that the ensemble
means indicate increased QPF across the state. Thus there is still
some uncertainty and the forecast will continue to be monitored.
Somewhat more predictable is that the atmosphere should gradually
moisten into late week while a weak west-east front may push
through the state slowly. This could increase coverage of
windward/mauka showers late week into the weekend regardless of
how close the low to the west gets.

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