High Surf Warning 10, NWS Honolulu, HI

Area Forecast Discussion
National Weather Service Honolulu HI
950 AM HST Thu Dec 1 2022

.SYNOPSIS...
Light to moderate trade winds will strengthen somewhat over the
weekend, bringing a few brief windward showers. Increasing moisture
and strengthening southeast winds may bring more showers next week.

&&

.DISCUSSION...

Current satellite and radar imagery shows moderate northeast
winds focusing low level clouds and showers along the windward
coasts while light winds support extensive cloud cover wrapping
around the Big Island to coastal leeward areas. Early morning
soundings show more dry and stable conditions over Kauai than the
Big Island which is in line with satellite precipitable water
imagery showing drier conditions moving in from the north over
Kauai and lingering moisture around the Big Island. By tonight,
hi-res models indicate that this moisture will support increasing
showers over downslope areas of Windward Big Island as stronger
easterly trades build into the area. Increased showers, mainly
over windward and mauka areas, will then spread over the
remainder of the island chain late tonight through early Friday. A
slight chance of showers and thunderstorms remains in the forecast
over the Mauna Loa summit where lava-induced extreme heating of
the lower atmosphere will spur occasional development of
pyrocumulonimbus clouds.

Early next week, a strong ridge aloft well W of the area will
allow for the downstream development of a large cutoff low,
roughly along the longitude of the islands. Latest guidance
indicates the low will develop just W of the islands, then drift
W. This would lead to a strengthening of the ridge aloft over the
islands, and a relatively strong surface high pressure cell to the
NE that will support locally strong E-SE trade winds. Depending
on the eventual location of the low, associated convergence bands
could bring increased showers to the W end of the island chain by
the middle of next week.

&&

.AVIATION...

Light winds today will be transitioning to a moderate trade wind
flow over the next 24 hours or so, as high pressure builds to the
north, and moves to the northeast of the islands. Winds will be
light enough today that some areas will see some afternoon sea
breezes. Clouds will be focused over the north through east
sections of the islands, along with afternoon clouds over the
Kona slopes of the Big Island. Expect passing showers, with some
MVFR conditions possible, but overall VFR conditions are expected
to prevail.

Winds are expected to remain light today, so not expecting any
turbulence issues. As the trades strengthen, there will be the
possibility for AIRMET Tango for mechanical turbulence.

&&

.MARINE...

Large surface high pressure north of the islands will maintain
moderate trade winds through late today. A building large
northwest swell will peak later today and select waters exposed to
the northwest swell should see seas reach the Small Craft
Advisory threshold of 10 feet tonight. A Small Craft Advisory has
been issued for these exposed waters. Moderate trades will veer
more easterly Friday and persist well into next week. An
approaching cold front from the northwest may hang up just west of
the state early next week and veer winds more south of east.

A large, long period west northwest (300-310 degree) swell will build
in today, peak this afternoon through tonight then gradually fall
Friday into the weekend. Due to buoy readings at buoy 51101 and
51001 running 3 to 4 feet above wavewatch3 guidance, the High Surf
Advisory was upgraded to a High Surf Warning for most north and
west facing shores of the smaller islands. Also a High Surf
Advisory was issued for the west facing shores of the Big Island
starting tonight and continuing through Friday. A northeast swell
moving into our nearshore windward waters Saturday may also lift
north and east-facing shore surf across the state to near HSA
levels over east facing shores this weekend.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Warning until 6 AM HST Friday for Niihau-Kauai Leeward-
Waianae Coast-Oahu North Shore-Maui Windward West-Kauai North-
Molokai Windward-Molokai North-Molokai West-Windward Haleakala.

High Surf Advisory from 6 AM to 6 PM HST Friday for Niihau-Kauai
Leeward-Waianae Coast-Oahu North Shore-Maui Windward West-Kauai
North-Molokai Windward-Molokai North-Molokai West-Windward
Haleakala.

High Surf Advisory from 6 PM this evening to 6 PM HST Friday for
Kona-Kohala.

Small Craft Advisory from 6 PM this evening to 6 AM HST Friday
for Kauai Northwest Waters-Kauai Windward Waters-Kauai Leeward
Waters-Kauai Channel-Oahu Windward Waters-Kaiwi Channel-Maui
County Windward Waters.

&&

DISCUSSION...Almanza/JVC
AVIATION...M Ballard
MARINE...Ciofi/Kino