High Surf Advisory 1, NWS Honolulu, HI

045 
WHHW40 PHFO 030117
CFWHFO

Coastal Hazard Message
National Weather Service Honolulu HI
317 PM HST Sat Jan 2 2021


HIZ001>003-006>008-012-013-017-019-020-030230-
/O.CAN.PHFO.SU.Y.0001.000000T0000Z-210103T0400Z/
Niihau-Kauai Windward-Kauai Leeward-Waianae Coast-
Oahu North Shore-Oahu Koolau-Molokai Windward-Molokai Leeward-
Maui Windward West-Maui Central Valley-Windward Haleakala-
317 PM HST Sat Jan 2 2021

...HIGH SURF ADVISORY IS CANCELLED...

Surf along the north and west facing shores has dropped below
advisory levels as the swell continues to subside.

$$

Area Forecast Discussion...CORRECTED
National Weather Service Honolulu HI
145 AM HST Sat Jan 2 2021

.UPDATE...
The winds atop Big Island summits have hit the wind advisory
criteria of 45 mph or higher. Hence, a wind advisory is now in
effect to until 6 pm HST Saturday.

&&

.SYNOPSIS...
An area of high pressure located 1050 miles northeast of the
islands will continue to move east through Monday. This action
will result in weakening trade winds, trending down to light to
moderate speeds by Monday night, then hold through Wednesday.
Showers may become less frequent with the diminishing trades.

&&

.DISCUSSION...
The wind situation this evening is still quite windy in some spots
over on the eastern islands, but overall it is on its way down.
Perhaps one more day of breezy conditions. The wind advisory that
is good to 4 am HST Saturday still stands, and will likely be
canceled at 4 am HST Saturday. The winds atop Mauna Kea is blowing
just below advisory threshold, and will be monitored closely
overnight. Trade winds will likely be down to light to moderate
speeds by Monday night, then hold through at least the middle of
next week. This weakening trend is in response to the surface high
moving further away from the islands. The high is currently
located 1050 mile northeast of the islands. The region may
encounter less frequent trade wind showers with the weaker
trades.

The weakening trend with the trades usually means a front is
approaching the islands from the west. And this is what it is. A
front is expected to weaken and pass north of the islands on
Wednesday. That is all for now.

Satellite imagery shows widely dispersed clouds upwind of all the
islands. Radar is picking up a few showers with these clouds on
just about all the islands exposed to this flow. Do expect an
uptick in the clouds and showers, especially after midnight. The
frequency of these showers will become less by mid or late morning
Saturday, with ample of sunshine along the leeward shores in the
afternoon. The lee side of the Big Island is mainly clear this
evening, which is uncommon from the afternoon and evening clouds.

&&

.AVIATION...
A high pressure system passing by north of the Hawaiian Islands
will keep breezy trade winds in the forecast through this weekend.
Low level winds this strong will produce moderate turbulence below
8000 feet over and south through west of all island mountains. A
jet stream passing over the Big Island will produce Severe Clear
Air Turbulence near the Big Island and Maui this evening between
FL290 and FL430.

Expect passing showers favoring windward and mountain areas with
more isolated showers over leeward slopes. Tempo Mountain
Obscuration is possible over the windward slopes of some islands
later tonight.

&&

.MARINE...
Strong east-northeast trade winds will continue into Saturday, then
gradually trend down Sunday through the first half of the upcoming
week. The Small Craft Advisory will remain in place through the
weekend due to a combination of winds and seas. This advisory will
likely continue through the first half of the week due to seas as
overlapping large northwest swells move through. Although confidence
is low being this far out, winds may drop enough for localized land
and sea breeze conditions by midweek as a weakness forms in the
ridge to the north in response to a front passing.

Surf along north facing shores will ease into Saturday, potentially
below advisory levels by Saturday night. The offshore buoys to the
north and northwest reflect this downward trend this evening with
the peak swell energy in the 14-16 second bands out of the north-
northwest (330 deg). The active pattern across the northern Pacific
is forecast to continue over the weekend through next week with a
series of systems sending overlapping northwest swells through the
islands. The first in the series should begin to fill in through the
day Saturday and Saturday night (out of 320 deg), then peak Sunday
night into Monday near warning levels. Guidance depicts this episode
slowly lowering to advisory levels for north and west facing shores
Tuesday.

A large fetch setting up over the northwest Pacific within the 310-
330 directional bands relative to the islands shown in the guidance
Sunday through Monday will potentially deliver the next warning-
level event to exposed north and west facing shores come
Wednesday. A similar pulse arriving Friday into Saturday is shown
following this.

Although lowering daily tidal ranges will limit the extent of the
wave runup next week, overlapping large northwest swells described
above will only worsen the ongoing coastal erosion issues for
vulnerable shores exposed to north and west swells. Peak monthly
tides for January are expected from the 10th through the 15th.

Surf along east facing shores will remain near the advisory level of
8 ft (faces) over the weekend, then gradually lower early next week
as the trades ease.

&&

.FIRE WEATHER...
Trade winds will remain breezy through the weekend, and leeward
relative humidity values will drop down to 50 percent or less each
afternoon. With abnormally dry long term conditions in place over
leeward areas, there will be elevated fire weather concerns,
though Red Flag Warnings do not appear likely.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Warning until 4 AM HST Saturday for Niihau-Kauai
Windward-Kauai Leeward-Waianae Coast-Oahu North Shore-Oahu
Koolau-Molokai-Maui Windward West-Maui Central Valley-Windward
Haleakala.

Wind Advisory until 4 AM HST Saturday for Lanai-Kahoolawe-Maui
Windward West-Maui Leeward West-Maui Central Valley-Windward
Haleakala-Leeward Haleakala-South Big Island-Big Island North
and East-Kohala.

Wind Advisory until 6 PM HST Saturday for Big Island Summits.

Small Craft Advisory until 6 PM HST Sunday for Kauai Northwest
Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel-
Oahu Windward Waters-Kaiwi Channel-Maui County Windward Waters-
Maalaea Bay-Pailolo Channel-Alenuihaha Channel-Big Island
Windward Waters-Big Island Leeward Waters-Big Island Southeast
Waters.

Small Craft Advisory until 6 PM HST Saturday for Oahu Leeward
Waters-Maui County Leeward Waters.

&&

H Lau/Bohlin/Gibbs