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Hawaiian Islands Synoptic Discussion and Guidance

FXHW60 PHFO 050152

Area Forecast Discussion
National Weather Service Honolulu HI
352 PM HST Mon Dec 4 2023

Dry and stable trade wind conditions are expected through midweek,
with the best rainfall chances favoring our windward and mauka
locations overnight through the morning periods. A few showers
could make it into our leeward areas, especially as the trades
become gusty tonight through Tuesday. A return of light winds and
increasing moisture associated with an approaching front could
bring the rainfall chances up late Thursday through the weekend,
especially over the western end of the state as the front begins
to weaken and stall.


High pressure systems are centered far northeast and northwest of
Hawaii driving moderate trade winds. A slow moving and weak cold
front 300 miles north of Kauai separates the highs. While mostly
dry and stable conditions will prevail over the next couple days,
trades will carry in low clouds and showers that will favor
windward and mauka locations, with the best chances being
overnight through the early morning hours. Although the tail-end
of the passing front should stall and dissipate nearby to the
north Tuesday through Wednesday, the leading edge of the moisture
axis could make it as far south as Kauai late Tuesday into Tuesday
night, which would support better windward shower coverage.
Elsewhere, dry and stable conditions will limit rainfall
accumulations. The trades are expected to peak in the breezy
category Tuesday as the high to the northwest moves eastward and
may bring a few of those incoming showers onto leeward sides of
the smaller islands.

Despite some model differences in timing, a general consensus
supports the ridge to the north weakening and shifting southward
beginning Thursday as a shortwave trough and surface cold front
approach from the northwest. Surface winds will respond and
become light out of the southeast Thursday. A combination of
light winds, increasing moisture, and lowering upper heights will
support better rainfall coverage over the western end of the state
where the front will weaken and begin to stall. Light winds may
linger into the weekend before trades gradually return Sunday into
next week.


High pressure north of the state will drive moderate to locally
breezy trade winds through Tuesday. Dry and stable conditions will
keep clouds and showers over mainly windward and mauka areas, with
periods of MVFR possible under passing showers. Otherwise, expect
mainly VFR conditions across the state.

No SIGMETs are in effect nor expected through Tuesday.


A high far northwest of the main Hawaiian Islands will tighten
the pressure gradient across the region and strengthen trade winds
into the fresh to strong category by Tuesday morning. After
Wednesday, a weak front approaching from the northwest will cause
winds to weaken again. This front may reach far northwest waters
by the weekend. A large swell created by a hurricane force low
far north of the islands will begin arriving tonight. A Small
Craft Advisory (SCA) for seas remains in effect for all waters
through Wednesday afternoon.

A High Surf Advisory (HSA) remains in effect for most north and
west-facing shores of the smaller islands through Tuesday
afternoon. The current north-northwest (320-340 degrees) swell
will be reinforced by the next one generated by the hurricane
force low beginning tonight. This large, long-period swell will
peak Tuesday and boost surf heights along north and west-facing
shores to High Surf Warning (HSW) levels Tuesday morning. This
swell will slowly decline Tuesday night through the remainder of
the week. Strengthening trades over the next couple of days will
increase east-facing shore surf and lead to rough conditions from
Tuesday into the middle of the week.


High Surf Advisory until 6 PM HST Tuesday for north and west
facing shores of Niihau, Kauai, Oahu, Molokai and north facing
shores of Maui.

Small Craft Advisory until 6 PM HST Wednesday for all Hawaiian




Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office