High Surf Warning 7, NWS Honolulu, HI

Area Forecast Discussion
National Weather Service Honolulu HI
930 AM HST Fri Apr 4 2025

.SYNOPSIS...
Breezy trades will focus showers associated with a dissipating
front over Oahu and Kauai into Saturday while dry weather and
light winds prevail elsewhere. Trades then return to the
remainder of the area tonight and continue through next week.

&&

.DISCUSSION...

Regional observations and model analyses this morning reveal a
dissipating cold front stalled in the Kauai Channel beneath a mostly
opaque canopy of high clouds aloft. Strong southwesterlies aloft
ensure high clouds will persist for the balance of the day helping
to tamp down temperatures. However, mixing depths will also be
suppressed, which will likely reduce any gust component to the wind
while also maintaining slightly elevated dewpoints at the surface.
Radar composite shows the focus of showers extending from the Kauai
Channel to Oahu at press time as moderate to breezy trades make
their return to the western end of the state. This band of frontal
moisture will favor enhanced showers over windward and mauka
sections of Oahu and especially Kauai until building trades usher it
west of the state by late Saturday. Elsewhere, breezy trades
gradually return as governing high pressure becomes established near
30N. This in turn favors a return to a typical distribution of
clouds and showers over windward and mauka areas going forward.
Little change then for the remainder of the forecast period as
breezy trades prevail.

&&

.AVIATION...

A dissipating front over the western end of the state has stalled
across the Kauai Channel with breezy northeasterly trade winds
building in its wake. Enhanced clouds and showers over Kauai and
Oahu are expected through the morning as moisture lingers along
the dissipating front. Periods of MVFR conditions are likely
within the heavier showers, with brief periods of IFR possible. As
such, AIRMET Sierra is in effect for mountain obscuration for all of
Kauai and Oahu through the morning.

The eastern half of the state will see moderate to locally breezy
southeasterly winds through the afternoon before easterly trade
winds return tonight. Overall, VFR conditions will prevail across
this end of the state.

AIRMET Tango is in effect for tempo moderate upper level
turbulence and is expected to continue through the morning.

&&

.MARINE...

Trade winds will build today and become locally strong and gusty
during the weekend. A dissipating front stalled just north and
west of Oahu will drift westward over Kauai tonight and Saturday.
Meanwhile, strong high pressure far northwest of the state will
build and creep eastward. As a result, trade winds will gradually
strengthen today, especially around Kauai, where a Small Craft
Advisory (SCA) is in effect. SCA strength winds will develop
across the typically windy waters around the Big Island and Maui
County tonight and will persist through at least Sunday. Trades
will likely ease slightly Monday and Tuesday as the surface high
weakens, but trades are expected to build again by Wednesday.

A north-northwest (330-340 deg) swell will arrive today, followed
by a large north (340-350 deg) swell Saturday and Sunday. Recent
observations from buoy 51001 have shown the new north-northwest
swell at 7 to 8 feet with the energy spread out between periods of
11 to 14 seconds, and surf along north facing shores will build
close to High Surf Advisory levels this afternoon and tonight. A
much larger pulse of long period north swell will rapidly build
late Saturday and peak Saturday night and Sunday. During the peak,
surf along north and exposed east facing shores of most islands
should reach High Surf Warning levels, while most west facing
shores experience advisory level conditions. Moderate to heavy
surges in north facing harbors, mainly at Kahului and Hilo, are
anticipated by Saturday and will persist through the weekend. The
large swell will also produce combined seas in excess of 10 feet
over most waters and will contribute to the need for a SCA. The
north swell will steadily decline on Monday and will fade by the
middle of next week.

Small surf will prevail along south facing shores during the next
couple of days. Small pulses of south swell are possible late
Sunday and Monday and again midweek.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 AM HST Saturday for Kauai Northwest
Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel.

&&

DISCUSSION...JVC
AVIATION...Farris
MARINE...Wroe