Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
313 AM EST Fri Dec 03 2021

Valid 00Z Sat Dec 04 2021 - 00Z Sat Dec 11 2021

Active weather will continue over Hawaii through this weekend and
well into next week. A closed upper low is forecast to spin north
of the state (around 35N/155W) through the weekend, while at the
surface, a cold front passing through much of the state today into
Saturday before stalling will help to focus moisture especially
over the Big Island and Maui. The enhanced moisture should lead to
increased coverage of showers for those areas. Additionally, gusty
northwesterly winds are forecast behind the cold front. The
highest elevations of the Big Island have Blizzard Warnings issued
by NWS Honolulu given the moisture in place with the stalled front
and windy conditions. Meanwhile, there is a Flood Watch in place
for most of the rest of the state.

By Sunday into Monday, the upper low is expected to reform/drift
southwestward to around 25N/165W, while an upper high resides well
east of the state, and a surface low and high generally reflect
the positions of the upper-level features. This pattern will lead
to mean southerly flow across Hawaii through much of the period,
bringing in ample tropical moisture northward from the ITCZ. Model
guidance agrees that precipitable water values will be over the
95th percentile around Monday-Wednesday, with the axis of highest
PWs drifting slowly east to west across the state. Heavy rainfall
should follow this pattern and several inches of rain can be
expected, along with flooding/flash flooding potential. By the
latter part of next week, the upper low is forecast to drift
westward while an upper high encroaches toward Hawaii, eventually
lessening heavy rain chances.

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