Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
256 AM EST Sun Jan 29 2023

Valid 00Z Mon Jan 30 2023 - 00Z Mon Feb 06 2023

Heavy rain and thunderstorms are likely to continue across Hawaii
over the next couple of days. Aloft, an elongated upper trough
sneaking southward into Hawaii still looks likely to pinch off
energy into a subtropical closed low centered over to just
southwest of the state by around 12Z Monday. This will draw in
deep tropical moisture as well as provide instability with a
removed inversion given the lowering heights aloft, for even more
support for widespread rain and thunderstorms. Moisture levels
will be quite high with precipitable water values showing to be
over the 90th or 95th percentiles. Meanwhile a surface trough will
continue to focus this moisture and gradually drift west over the
next couple days. All islands may be at risk of seeing very heavy
rain amounts and additional instances of flooding--the Big Island
where moisture levels are maximized and other islands particularly
as the trough passes over. Kauai could see a wetter trend over the
next couple of days along with their gusty north-northeasterly
winds on the backside of the trough/low. The Honolulu Forecast
Office has a Flash Flood Watch in place for much of the state.
Additionally, the summits of Mauna Kea and Mauna Loa have been and
could continue to see snow for another day or so given the lower
heights of the trough/low causing colder air in these highest
elevations, and Winter Storm Warnings are in effect.

By Tuesday and beyond, models generally indicate that the closed
upper low should drift a bit west away from the state but be slow
to erode. This will lead to less support for the heaviest rainfall
amounts, but above average moisture looks to stay in place through
midweek and beyond, but likely to a lesser extent. After a period
of some weak overall winds around midweek, the surface pattern
looks favorable for more typical easterly winds to form by later
in the week with a high to the north, so a wet trade wind pattern
looks to be in store.

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