High Surf in Hawaii, April 2 to 3, 2022

Area Forecast Discussion
National Weather Service Honolulu HI
330 AM HST Sat Apr 2 2022

.SYNOPSIS...
Trade winds will increase further and remain gusty through the
weekend. Rainfall will focus along windward slopes, with some
showers blowing over leeward areas from Maui to Kauai at times.
Afternoon showers will develop over the Kona slopes of the Big
Island. As trade winds ease, a disturbance aloft will produce
increasing high clouds Monday and may raise rain chances Tuesday.
Moderate trade winds and a typical windward rainfall pattern are
expected by the middle of next week.

&&

.DISCUSSION...
A high far north of Kauai is driving strong trade winds across
the area, with a stalled front between the islands and the high
preventing even stronger winds from developing. Weak upper ridging
seems to be capping shower intensity so far this morning. A
diffuse band of low level moisture embedded within the trades has
moved west of the state overnight, decreasing cloud and shower
coverage. With continued trade flow, expect rainfall to focus
along windward slopes, with showers periodically being blown
across leeward areas from Maui to Kauai.

Breezy and gusty trade wind weather will prevail through this
weekend. The high will move to a position north of the state, and
the front will dissipate. Trades will increase slightly and may
approach Wind Advisory strength across portions of the Big Island
and Maui County. The current rainfall pattern will continue, with
random pockets of moisture periodically enhancing showers.

Trade winds will decrease and shower chances may increase during
the first half of next week. Trades will ease as the high is
weakened and displaced eastward by a front. The upper ridge will
be eroded by a deepening upper trough, leading to increased
instability. The initial result will be thickening high clouds on
Monday, and as the upper trough moves overhead on Tuesday, shower
chances may increase. The upper trough will move out Wednesday
and Thursday, bringing back stability as trades rebound.

&&

.AVIATION...
Breezy to strong trade winds continue to affect the island chain
as robust high pressure remains far to the north. Showery low
cloudiness, with accompanying MVFR ceilings and visibilities,
is riding on the trades and has been mainly affecting windward
and mauka sections, though occasionally moving over leeward areas
from time to time as well.

An AIRMET for TEMPO mountain obscuration is posted for most
islands because of the broken to occasionally overcast low clouds
moving through the area. Another AIRMET for low level turbulence
to the lee of the islands remains in effect.

&&

.MARINE...
A strong surface high pressure system centered far north of the
islands, which is moving east slowly, is generating strong trade
winds across the state this weekend. In addition, combined seas
will remain elevated and rough over waters exposed to the strong
trades and a northwest swell. A Small Craft Advisory (SCA) is in
effect for all Hawaiian waters through early Sunday morning, and
will likely be extended through the day on Sunday for most of the
same area. The SCA may be scaled back from Sunday night into
Monday to include only the typically windier waters adjacent to
the islands of Maui County and the Big Island. The surface high
will eventually weaken northeast of the area early next week,
which will cause the trade winds to gradually ease from late
Monday through Tuesday.

Observations from the Hanalei Buoy near the north shore of Kauai
show the current northwest swell is about one foot above the wave
model guidance. The swell is expected to peak later this morning,
and a High Surf Advisory (HSA) remains in effect through this
afternoon for the north and west facing shores of Kauai, Niihau,
Oahu, and Molokai, and for north facing shores of Maui. This swell
is forecast to gradually lower later today and tonight, but we
will monitor observations in case the HSA needs to be extended
into this evening. The northwest swell will continue to slowly
lower from Sunday through early next week. A mix of small
northwest and north-northwest swells will produce modest surf
along most north and west facing shores during the middle of next
week.

The strong trade winds will cause surf to build along east facing
shores, and it will likely remain elevated and rough through
Sunday night. By early next week, the weakening trade winds will
cause the surf to gradually lower along east facing shores.
Background south swell energy will maintain small, near seasonal
surf heights along most south facing shores. Note that the trade
wind wrap may produce slightly elevated surf along some shorelines
with an east exposure this weekend, such as along the coast of
the southeast Big Island.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory until 6 PM HST this evening 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.

Small Craft Advisory until 6 PM HST Sunday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big
Island Southeast Waters.

Small Craft Advisory until 6 AM HST Sunday for Kauai Northwest
Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel-
Oahu Windward Waters-Oahu Leeward Waters-Kaiwi Channel-Maui
County Windward Waters-Maui County Leeward Waters-Big Island
Windward Waters.

&&

DISCUSSION...Powell
AVIATION...Kinel
MARINE...Houston