High Surf in Hawaii, November 24 to 26, 2021

Area Forecast Discussion
National Weather Service Honolulu HI
359 PM HST Wed Nov 24 2021

.SYNOPSIS...
Trade winds will pick up to moderate speeds on Thursday then
gradually decline Friday into Saturday. An increase in moisture
over the eastern end of the state tonight and tomorrow will boost
rainfall there, particularly over windward Big Island and east
Maui. The remainder of the state will remain on the drier side
with some scattered shower through the end of the week. Breezy
trade winds will likely return Sunday into early next week.

&&

.DISCUSSION...
Although some sea breezes developed in some select areas this
afternoon, for the most part we saw light trade wind conditions
across the state. Trade winds should briefly pick up on
Thanksgiving with widespread moderate speeds expected.

An area of higher moisture will begin approaching the Big Island
this afternoon and steadily increase overnight tonight into
Thursday. At the same time, a weak upper level low will move over
the Big Island on Thursday will cause the trade wind inversion to
dissipate. This will allow for deeper moisture and should
translate to moderate to locally heavy showers over windward Big
Island and east Maui. Over the rest of the state some passing
showers are expected Thursday, but rainfall intensities will be
much lighter than windward areas of Big Island and Maui.

Starting Friday a drier air mass will move into the eastern end
of the state and we should see a drier than normal trade wind
pattern across the state. A front passing north of the state on
Saturday will cause the winds to weaken over the state. Light
northeasterly winds are expected on Saturday with fair weather
conditions. Winds should be light enough for localized sea breezes
by midday Saturday. As this front moves northeast and away from
the state, high pressure will build north of the state on Sunday.
Moderate to locally breezy trade winds could return as early as
Sunday.

In the extended forecast, global models are in fairly good
agreement with an upper level low dropping down and cutting off
just east of the Big Island Sunday night into the first half of
next week. A strong jet is associated with the low as it begins to
drop south toward the state on Sunday and this could bring strong
and gusty winds over the summits of the Big Island and possibly
Haleakala Sunday into Monday. Further out, the forecast will
depend on the location of this upper level low. If the low ends up
drifting more westward and toward the state, we could see a wet
weather pattern. Stay tuned for more details.

&&

.AVIATION...
Light to moderate easterly trade winds will persist through this
evening and into tonight. Thus, isolated to scattered showers
will mainly affect windward coasts and slopes of the western most
smaller islands with scattered to numerous showers poised to
affect windward Maui and the Big Island. Periods of MVFR ceilings
and visibility may accompany this activity.

No AIRMETs are currently in effect.

&&

.MARINE...
Surface high pressure is centered far northeast of the area with
a ridge axis extending southwest to a position just north of
Kauai. This places the area in a light to locally moderate
easterly trade wind environment. The stronger winds are around the
Big Island with the lighter winds over the western waters. This
overall wind pattern is expected through Saturday night. A new
high will build in north of the area on Sunday and Monday with
northeast trade winds expected to increase across the entire area.

A new northwest swell will continue to fill in overnight, peak on
Thursday, then lower slowly Friday and Saturday. Open ocean swell
heights are expected to peak around 8 to 9 feet. Surf heights are
expected to reach low end advisory levels during the peak of the
swell. A High Surf Advisory has been issued for exposed north and
west facing shores. Another similar size northwest swell is
expected to fill in Saturday night, peak on Sunday, then lower
slowly Monday and Tuesday. Advisory level surf is likely with this
swell as well.

With trade winds being on the lighter side, short period choppy
surf will be rather small along east facing shores through
Saturday with an uptrend expected beginning Sunday and continuing
on into early next week as trade winds increase over and upwind
of the state. South facing shores will only experience small
background swell energy throughout the forecast period.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory from 6 AM Thursday to 6 AM HST Friday for
Niihau-Kauai Leeward-Waianae Coast-Oahu North Shore-Maui
Windward West-Kauai North-Molokai Windward-Molokai North-Molokai
West-Maui Central Valley North-Windward Haleakala.

&&

DISCUSSION...Kino
AVIATION...Thomas
MARINE...Burke