High Surf in Hawaii, March 7 to 10, 2023

Area Forecast Discussion
National Weather Service Honolulu HI
403 PM HST Tue Mar 7 2023

.SYNOPSIS...
A strong cold front approaching Kauai will sweep from west to
east down the island chain tonight through Wednesday night,
bringing showers and windy conditions to the state. Winds will
ease with drier and cooler conditions filtering into the islands
Thursday through the weekend. Warmer weather will return early
next week.

&&

.DISCUSSION...
Currently at the surface, a weakening front is east of Big
Island, while a stronger cold front is located around 150 miles
west- northwest of Kauai. Visible satellite imagery shows partly
to mostly cloudy conditions across the state. Radar imagery shows
the rainband that was over Oahu early this morning is now over
Maui County. Another rainband associated with the approaching
frontal band is now moving over Niihau and Kauai.

The main short term focus still revolves around the approaching
front and the potential for strong southwesterly winds across the
island chain tonight and Wednesday. Breezy west to southwest
winds this evening will continue to gradually strengthen to windy
west southwest winds by midnight tonight and remain windy through
Wednesday evening. As a result, a Wind Advisory remains in effect for
the entire state beginning midnight tonight through 12 AM
Thursday, with gusty downslope winds in excess of 50 mph likely
over the windward areas northeast of the mountains. The unusual
wind direction and well soaked soils will increase the potential
for impacts in the form of falling trees or possible landslides.
On the summits of the Big Island, a High Wind Warning remains in
effect through 6 PM Sunday. On the Haleakala summit, the High Wind
Watch has been upgraded to a High Wind Warning which will go into
effect at 6 PM this evening through 6 AM Thursday.

In addition to strong winds, fairly showery weather can be
expected with the frontal passage beginning this evening around
Kauai, then central islands late tonight and Wednesday, with some
showery weather likely to continue over the Big Island Wednesday
night. Showers will mainly be focused over leeward areas and
diminish behind the front.

Winds will ease to moderate levels Thursday and become light
Friday through early next week as a weak ridge slides eastward
over the island chain. Drier conditions will encompass the entire
state Thursday through Monday allowing for noticeably cooler
conditions. Dewpoints are expected drop into the 50s. Maximum
high temperatures will struggle to reach 80 degrees, and lows will
bottom out in the upper 50s to lower 60s Thursday through
Saturday.

&&

.AVIATION...
Southwest winds will strengthen as a cold front approaches Hawaii
from the northwest tonight into Wednesday. AIRMET Tango is also
posted for tempo low level moderate turbulence along northeast
sides of all islands due to the strengthening southwest winds.

AIRMET Sierra is posted for tempo mountain obscurations above
2500 feet for the leeward side of Kauai. AIRMET Sierra will likely
be expanded to islands eastward as the front advances and brings
more widespread clouds and showers. A pre-frontal cloud/shower
band is set up across Maui County bringing brief MVFR ceilings and
visibility tonight.

&&

.MARINE...
Southwest to west winds will increase as a cold front, currently
moving over waters west of Kauai this afternoon, passes over Oahu
waters overnight, then sweeps down the rest of the island chain
Wednesday. Strong to near gale force west winds developing late
tonight and Wednesday will be driven by the circulation around the
front's parent low, which will pass less than 500 nm north of the
state. A Small Craft Advisory (SCA) is in effect for all waters
tonight through Wednesday night. Westerly winds will gradually
ease Thursday and Friday, though seas should remain above the 10
foot SCA threshold into Friday for most areas. Gentle to locally
moderate westerly winds will likely prevail this weekend.

Generally small surf is due through the evening, followed by very
large, rough, and hazardous seas Wednesday and Thursday. In the
short term, short-period northwest swell will produce surf well
below seasonal average this evening. A very large northwest swell
(310-320 degrees) will build late tonight and Wednesday, peak
Wednesday night, then slowly decline Thursday and Friday. As
expected, there is no sign of the swell on the NOAA buoys
northwest of Kauai this afternoon, but overnight altimeter passes
verified guidance, showing seas of 30 to 34 ft in the source
region of the swell about 1000 nm northwest of Kauai. The storm
producing the swell will continue to advance southeastward at a
very low latitude through Wednesday, and its captured fetch will
generate a large swell, likely in excess of 20 ft during the peak,
across Hawaiian waters Wednesday into Thursday. Surf will exceed
High Surf Warning levels along most north and west facing shores,
including the leeward Big Island by Wednesday evening, and due to
large wind waves from the strong west winds and a mix of medium
and longer period swell energy, rough conditions could lead to
overwash of some coastal infrastructure and beach erosion, mainly
Wednesday evening through Thursday morning along exposed north and
west facing shores. The swell will decline and shift out of the
north-northwest Friday through the weekend.

Minimal trade wind swell is expected this week, though there is
some potential for localized wave wrap along east facing shores
exposed to the large northwest swell from late Wednesday into
Friday. Rough surf may briefly increase along south facing shores
as the front moves down the island chain late tonight and
Wednesday.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from midnight tonight to 12 AM HST Thursday night
for Niihau, Kauai, Oahu, Molokai, Lanai, Kahoolawe and lower
elevations of Maui and the Big Island.

High Surf Warning from 6 AM Wednesday to 6 PM HST Thursday for
north and west facing shores of Niihau, Kauai, Oahu and North
facing shores of Maui.

High Wind Warning from 6 PM this evening until 6 AM HST Thursday
for Haleakala Summit.

High Surf Warning from 6 PM Wednesday to 6 PM HST Thursday for
west facing shores of the Big Island.

High Wind Warning until 6 PM HST Sunday for Big Island Summits.

Small Craft Advisory until 6 AM HST Thursday for all waters.

&&

DISCUSSION...Almanza/Vaughan
AVIATION...Foster
MARINE...Wroe