Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
307 AM EST Fri Jan 27 2023

Valid 00Z Sat Jan 28 2023 - 00Z Sat Feb 04 2023

A frontal boundary stalled near the Big Island will remain that
way for the latter part of this week but likely weaken into a
trough. It should still provide convergence for moisture to pool,
however, and showers are likely to continue across the Big Island
into Maui through Friday/Friday night, with a drift of the trough
and shower axis westward a bit into the central islands by
Saturday per the HREF and other model guidance. Meanwhile Kauai
and Oahu are likely to see drier and breezier conditions on the
other side of this surface feature.

In the upper levels, a closed low is in place centered around 35
degrees north. Its center may drift north a bit over the next
couple days, but its associated trough is forecast to lengthen,
with upper-level energy drifting southward over the state and
closing off a subtropical upper low by around 12Z Monday perhaps
centered just to the southwest of Hawaii. This will draw in deep
tropical moisture as well as possibly providing instability with a
removed inversion given the lowering heights aloft. There are some
differences in timing of the peak of the highest moisture
anomalies (likely over the 90th or 95th percentiles for
precipitable water values) and thus the heaviest precipitation,
with the GFS runs peaking Sunday-Monday and the ECMWF peaking
Monday-Tuesday. But generally by early next week, widespread rain
and thunderstorms are likely, with models indicating the heaviest
totals over the Big Island. Instances of flooding are certainly
possible. Meanwhile Kauai and Oahu will start out on the backside
of the upper trough/low and could see continued breezy
north-northeasterly winds through early next week before the upper
low may drift over them. Models generally indicate that this
pattern could be slow to erode, with chances for showers and
storms continuing into the latter half of next week as well,
though likely to a lesser extent.

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