High Surf in Hawaii, January 4 to 8, 2021

Area Forecast Discussion...UPDATED
National Weather Service Honolulu HI
644 AM HST Mon Jan 4 2021

.SYNOPSIS...
A ridge north of the area will maintain moderate trade winds
through Thursday. Showers will be focused over mainly windward
areas, especially during the night and morning hours. The ridge
will move over the area Friday, bringing light and variable winds

&&

.DISCUSSION...
A progressive and zonal weather pattern across the North Pacific
basin will keep high and low pressure systems passing by north of
the state with little impacts to local Hawaiian weather until
Friday and Saturday. Breezy trade winds this past weekend will
weaken a bit to moderate levels from Monday through Thursday.
Clouds and passing showers will favor windward and mountain areas
during this period with typical higher trends in the overnight to
early morning hours. A brief increase in the trade wind speeds are
forecast from Wednesday night into Thursday as a stronger high
pressure system moves across the basin north of the island chain.
This increase in trade winds will be brief, as the high center
quickly moves eastward away from the area with light winds
developing over the region by Friday.

From Friday through Sunday, a cold frontal trough moves into the
region from the north, weakening the high pressure ridge north of
the island chain, and causing trade winds to vanish on Friday and
Saturday. This pressure pattern change with weakening large scale
winds will allow local scale land and sea breezes to develop
across the main Hawaiian Islands. Weather patterns will then shift
to clouds building over island mountain and interior sections
with afternoon sea breeze convergence. A few showers will develop
in this pattern mainly in the afternoon to early evening hours as
the converging sea breezes begin to decrease. Offshore land
breezes will begin around sunset, clearing out most of the cloud
cover. A weak background easterly wind will modify the land and
sea breeze regime on Sunday with a slight increase in windward
clouds and shower activity.

&&

.AVIATION...
Trade winds will continue to trend down today, potentially enough
for localized sea breezes across some leeward areas through
the afternoon hours. Although VFR conditions will prevail through
much of the 24-hr period, spotty windward showers will bring
brief periods of MVFR CIGS/VSBYS - mainly overnight through the
early morning hours.

There are no AIRMETs in place at this time.

&&

.MARINE...
A ridge north of the area will maintain gentle to locally fresh
trade winds through Thursday. Winds will shift out of the
southeast and weaken Friday as the ridge shifts south.

Swell heights at the NOAA buoys northwest of the main islands
are high enough to generate advisory level surf across exposed
shores, so a High Surf Advisory is now in effect for north and
west facing shores of Niihau, Kauai, Oahu and Molokai as well as
for north facing shores of Maui. This advisory is in effect
through Tuesday afternoon, but may need to be extended. A larger
northwest swell is forecast to build Tuesday night, with another
large northwest swell expected Wednesday night and Thursday. These
swells may produce warning level surf along north and west facing
shores Wednesday through Thursday. Surf is expected to drop back
below advisory levels by Friday night.

Surf along east facing shores will subside over the next few days
as trade winds weaken. South shore surf will remain small through
the coming week.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory until 6 PM Tuesday for north and west facing
shores of Niihau, Kauai, Oahu and Molokai and north facing shores
of Maui.

&&

DISCUSSION...Donaldson
AVIATION...Gibbs
MARINE...Powell